Showing 1–50 of 56 results for author: Olivero, P

Oxygen in diamond: thermal stability of ST1 spin centres and creation of oxygen-pair complexes

Authors: Paul Neugebauer, Xinxi Huang, Chloe Newsom, Christophe Arnold, Hjørdis Martelock, Séverine Diziain, Edoardo Monnetti, Jocelyn Achard, Tobias Lühmann, Paolo Olivero, Jan Meijer, Julien Barjon, Alexandre Tallaire, Sébastien Pezzagna

Abstract: Little is known about oxygen-related defects in diamond. Recently, the promising room-temperature spin centre named ST1 was identified as an oxygen centre, but of still unknown atomic structure and thermal stability. In this work, we report on the optically active oxygen-related centres and the conditions for their formation, using ion implantation of oxygen in various conditions of depth and flue… ▽ More Little is known about oxygen-related defects in diamond. Recently, the promising room-temperature spin centre named ST1 was identified as an oxygen centre, but of still unknown atomic structure and thermal stability. In this work, we report on the optically active oxygen-related centres and the conditions for their formation, using ion implantation of oxygen in various conditions of depth and fluence. More specifically, we establish the temperature formation/stability range of the ST1 centre, which has a maximum at about 1100°C and is narrower than for NV centres. In these conditions, optically detected magnetic resonance (ODMR) on small ST1 ensembles was measured with a spin readout contrast of > 20% at 300K. In cathodoluminescence, the 535 nm ST1 peak is not observed. Besides, a broad peak centred at 460 nm is measured for implantation of O$_2$ molecular ions. For an annealing temperature of 1500°C, a different centre is formed (with ZPL at 584.5 nm) with an intensity increasing with a power law 1.5 < p < 1.9 dependence from the implantation fluence. This suggests that this centre contains two oxygen atoms. Besides, a new spectral feature associated to an intrinsic defect was also observed, with four prominent lines (especially at 594nm). Finally, the thermal formation and stability of oxygen centres in diamond presented here are important for the identification of the atomic structure of defects such as the ST1 and possible O$_2$V$_x$ complex by means of ab initio calculations. Indeed, the formation energies and charge states of defect centres are easier to compute than the full energy level scheme, which to date still remains unsuccessful regarding the ST1 centre. △ Less

Submitted 7 January, 2026; originally announced January 2026.

Photoactivation of color centers induced by laser irradiation in ion-implanted diamond

Authors: V. Pugliese, E. Nieto Hernández, E. Corte, M. Govoni, S. Ditalia Tchernij, P. Olivero, J. Forneris

Abstract: Split-vacancy color centers in diamond are promising solid state platforms for the implementation of photonic quantum technologies. These luminescent defects are commonly fabricated upon low energy ion implantation and subsequent thermal annealing. Their technological uptake will require the availability of reliable methods for the controlled, large scale production of localized individual photon… ▽ More Split-vacancy color centers in diamond are promising solid state platforms for the implementation of photonic quantum technologies. These luminescent defects are commonly fabricated upon low energy ion implantation and subsequent thermal annealing. Their technological uptake will require the availability of reliable methods for the controlled, large scale production of localized individual photon emitters. This task is partially achieved by controlled ion implantation to introduce selected impurities in the host material, and requires the development of challenging beam focusing or collimation procedures coupled with single-ion detection techniques. We report on protocol for the direct optical activation of split-vacancy color centers in diamond via localized processing with continuous wave laser at mW optical powers. We demonstrate the activation of photoluminescent Mg- and Sn-related centers at both the ensemble and single-photon emitter level in ion-implanted, high-purity diamond crystals without further thermal processing. The proposed lithographic method enables the activation of individual color centers at specific positions of a large area sample by means of a relatively inexpensive equipment offering the real-time, in situ monitoring of the process. △ Less

Submitted 10 September, 2024; originally announced September 2024.

Comments: 17 pages, 7 figures

Creation, Control, and Modeling of NV Centers in Nanodiamonds

Authors: Pietro Aprà, Nour Hanne Amine, Adam Britel, Sofia Sturari, Veronica Varzi, Matteo Ziino, Lorenzo Mino, Paolo Olivero, Federico Picollo

Abstract: Sensing based on Nitrogen-Vacancy (NV) centers in nanodiamonds (NDs) offers significant potential across various applications. However, optimizing their quantum-optical properties remains challenging. This study focuses on enhancing and controlling the optical properties of NV centers in NDs through surface chemistry tuning and proton beam irradiation. Systematic thermal oxidations were performed… ▽ More Sensing based on Nitrogen-Vacancy (NV) centers in nanodiamonds (NDs) offers significant potential across various applications. However, optimizing their quantum-optical properties remains challenging. This study focuses on enhancing and controlling the optical properties of NV centers in NDs through surface chemistry tuning and proton beam irradiation. Systematic thermal oxidations were performed to investigate the evolution of surface chemical groups using IR spectroscopy and their influence on optical properties using photoluminescence spectroscopy and PL decay measurements. Proton irradiation was explored over a wide range of fluences (10^14 to 10^17 cm^-2) to precisely control the NV center concentration, identifying conditions that maximize creation and emission intensity. Furthermore, NV center charge state control was achieved by analyzing the NV-/NV0 ratio with varying surface terminations and NV center concentrations. A novel predictive mathematical model was developed to evaluate the efficiencies of forming NV- and NV0. Although tested specifically with proton-irradiated NDs, this model has broad applicability, representing a significant advancement in predicting the outcomes of ion-beam-based color center generation in diamond. △ Less

Submitted 1 July, 2024; originally announced July 2024.

4H-SiC Schottky diode radiation hardness assessment by IBIC microscopy

Authors: Ettore Vittone, Paolo Olivero, Milko Jaksic, Zeljko Pastuovic

Abstract: We report findings on the Ion Beam Induced Charge (IBIC) characterization of a 4H-SiC Schottky barrier diode (SBD), in terms of the modification of the Charge Collection Efficiency (CCE) distribution induced by 20 MeV C ions irradiations with fluences ranging from 20 to 200 ions/um2. The lateral IBIC microscopy with 4 MeV protons over the SBD cross section, carried out on the pristine diode eviden… ▽ More We report findings on the Ion Beam Induced Charge (IBIC) characterization of a 4H-SiC Schottky barrier diode (SBD), in terms of the modification of the Charge Collection Efficiency (CCE) distribution induced by 20 MeV C ions irradiations with fluences ranging from 20 to 200 ions/um2. The lateral IBIC microscopy with 4 MeV protons over the SBD cross section, carried out on the pristine diode evidenced the widening of the depletion layer extension as function of the applied bias and allowed the measurement of the minority carrier diffusion lengths. After the irradiation with C ions, lateral IBIC showed a significant modification of the CCE distribution, with a progressive shrinkage of the depletion layer as the fluence of the damaging C ions increases. A simple electrostatic model ruled out that the shrinkage is due to the implanted charge and ascribed the perturbation of the electrostatic landscape to radiation-induced defects with positive charge state. △ Less

Submitted 10 November, 2022; originally announced November 2022.

Magnesium-vacancy optical centers in diamond

Authors: Emilio Corte, Greta Andrini, Elena Nieto Hernández, Vanna Pugliese, Ângelo Costa, Goele Magchiels, Janni Moens, Shandirai Malven Tunhuma, Renan Villarreal, Lino M. C. Pereira, André Vantomme, João Guilherme Correia, Ettore Bernardi, Paolo Traina, Ivo Pietro Degiovanni, Ekaterina Moreva, Marco Genovese, Sviatoslav Ditalia Tchernij, Paolo Olivero, Ulrich Wahl, Jacopo Forneris

Abstract: We provide the first systematic characterization of the structural and photoluminescence properties of optically active defect centers fabricated upon implantation of 30-100 keV Mg+ ions in artificial diamond. The structural configurations of Mg-related defects were studied by the emission channeling technique for 27Mg implantations performed both at room-temperature and 800 °C, which allowed the… ▽ More We provide the first systematic characterization of the structural and photoluminescence properties of optically active defect centers fabricated upon implantation of 30-100 keV Mg+ ions in artificial diamond. The structural configurations of Mg-related defects were studied by the emission channeling technique for 27Mg implantations performed both at room-temperature and 800 °C, which allowed the identification of a major fraction of Mg atoms (~30-42%) in sites which are compatible with the split-vacancy structure of the MgV complex. A smaller fraction of Mg atoms (~13-17%) was found on substitutional sites. The photoluminescence emission was investigated both at the ensemble and individual defect level in a temperature range comprised between 5 K and 300 K, offering a detailed picture of the MgV-related emission properties and revealing the occurrence of previously unreported spectral features. The optical excitability of the MgV center was also studied as a function of the optical excitation wavelength enabling to identify the optimal conditions for photostable and intense emission. The results are discussed in the context of the preliminary experimental data and the theoretical models available in the literature, with appealing perspectives for the utilization of the tunable properties of the MgV center for quantum information processing applications. △ Less

Submitted 17 June, 2022; originally announced June 2022.

Comments: 7 figures

Spectral emission dependence of tin-vacancy centers in diamond from thermal processing and chemical functionalization

Authors: Emilio Corte, Selene Sachero, Sviatoslav Ditalia Tchernij, Tobias Lühmann, Sébastien Pezzagna, Paolo Traina, Ivo Pietro Degiovanni, Ekaterina Moreva, Paolo Olivero, Jan Meijer, Marco Genovese, Jacopo Forneris

Abstract: We report a systematic photoluminescence (PL) investigation of the spectral emission properties of individual optical defects fabricated in diamond upon ion implantation and annealing. Three spectral lines at 620 nm, 631 nm, and 647 nm are identified and attributed to the SnV center due to their occurrence in the PL spectra of the very same single-photon emitting defects. We show that the relative… ▽ More We report a systematic photoluminescence (PL) investigation of the spectral emission properties of individual optical defects fabricated in diamond upon ion implantation and annealing. Three spectral lines at 620 nm, 631 nm, and 647 nm are identified and attributed to the SnV center due to their occurrence in the PL spectra of the very same single-photon emitting defects. We show that the relative occurrence of the three spectral features can be modified by oxidizing the sample surface following thermal annealing. We finally report the relevant emission properties of each class of individual emitters, including the excited state emission lifetime and the emission intensity saturation parameters. △ Less

Submitted 14 June, 2021; originally announced June 2021.

Comments: 12 pages, 6 figures, 1 table

Spectral features of Pb-related color centers in diamond

Authors: Sviatoslav Ditalia Tchernij, Emilio Corte, Tobias Lühmann, Paolo Traina, Sébastien Pezzagna, Ivo Pietro Degiovanni, Georgios Provatas, Ekaterina Moreva, Jan Meijer, Paolo Olivero, Marco Genovese, Jacopo Forneris

Abstract: We report on the systematic characterization of the optical properties of diamond color centers based on Pb impurities. An ensemble photoluminescence analysis of their spectral emission was performed at different excitation wavelengths in the 405-520 nm range and at different temperatures in the 4-300 K range. The series of observed spectral features consist of different emission lines associated… ▽ More We report on the systematic characterization of the optical properties of diamond color centers based on Pb impurities. An ensemble photoluminescence analysis of their spectral emission was performed at different excitation wavelengths in the 405-520 nm range and at different temperatures in the 4-300 K range. The series of observed spectral features consist of different emission lines associated with Pb-related defects. Finally, a room-temperature investigation of single-photon emitters under 490.5 nm laser excitation is reported, revealing different spectral signatures with respect to those already reported under 514 nm excitation. This work represents a substantial progress with respect to previous studies on Pb-related color centers, both in the attribution of an articulated series of spectral features and in the understanding of the formation process of this type of defect, thus clarifying the potential of this system for high-impact applications in quantum technologies. △ Less

Submitted 2 June, 2021; originally announced June 2021.

Fluorine-based color centers in diamond

Authors: S. Ditalia Tchernij, T. Lühmann, E. Corte, F. Sardi, F. Picollo, P. Traina, M. Brajkovic, A. Crnjac, S. Pezzagna, I. P. Degiovanni, E. Moreva, P. Aprà, P. Olivero, Z. Siketić, J. Meijer, M. Genovese, J. Forneris

Abstract: We report on the creation and characterization of the luminescence properties of high-purity diamond substrates upon F ion implantation and subsequent thermal annealing. Their room-temperature photoluminescence emission consists of a weak emission line at 558 nm and of intense bands in the 600 - 750 nm spectral range. Characterization at liquid He temperature reveals the presence of a structured s… ▽ More We report on the creation and characterization of the luminescence properties of high-purity diamond substrates upon F ion implantation and subsequent thermal annealing. Their room-temperature photoluminescence emission consists of a weak emission line at 558 nm and of intense bands in the 600 - 750 nm spectral range. Characterization at liquid He temperature reveals the presence of a structured set of lines in the 600 - 670 nm spectral range. We discuss the dependence of the emission properties of F-related optical centers on different experimental parameters such as the operating temperature and the excitation wavelength. The correlation of the emission intensity with F implantation fluence, and the exclusive observation of the afore-mentioned spectral features in F-implanted and annealed samples provides a strong indication that the observed emission features are related to a stable F-containing defective complex in the diamond lattice. △ Less

Submitted 9 December, 2020; v1 submitted 28 September, 2020; originally announced September 2020.

Comments: 10 pages, 5 figures

Photoluminescence of lead-related optical centers in single-crystal diamond

Authors: S. Ditalia Tchernij, T. Lühmann, J. Forneris, T. Herzig, J. Küpper, A. Damin, S. Santonocito, P. Traina, E. Moreva, F. Celegato, S. Pezzagna, I. P. Degiovanni, M. Jakšić, M. Genovese, J. Meijer, P. Olivero

Abstract: We report on the creation and characterization of Pb-related color centers in diamond upon ion implantation and subse- quent thermal annealing. Their optical emission in photoluminescence (PL) regime consists of an articulated spectrum with intense emission peaks at 552.1 nm and 556.8 nm, accompanied by a set of additional lines in the 535700 nm range. The attribution of the PL emission to stable… ▽ More We report on the creation and characterization of Pb-related color centers in diamond upon ion implantation and subse- quent thermal annealing. Their optical emission in photoluminescence (PL) regime consists of an articulated spectrum with intense emission peaks at 552.1 nm and 556.8 nm, accompanied by a set of additional lines in the 535700 nm range. The attribution of the PL emission to stable Pb-based defects is corroborated by the correlation of its intensity with the implantation fluence of Pb ions, while none of the reported features is observed in reference samples implanted with C ions. Furthermore, PL measurements performed as a function of sample temperature (143-300 K range) and un- der different excitation wavelengths (532 nm, 514 nm, 405 nm) suggest that the complex spectral features observed in Pb-implanted diamond might be related to a variety of different defects and/or charge states. This work follows from previous reports on optically active centers in diamond based on group IV impurities, such as Si, Ge and Pb. In perspective, a comprehensive study of this set of defect complexes could bring significant insight on the common features involved in their formation and opto-physical properties, thus offering a solid basis for the devel- opment of a new generation of quantum-optical devices. △ Less

Submitted 5 June, 2018; originally announced June 2018.

Comments: 7 pages, 4 figures

Photo-physical properties of He-related color centers in diamond

Authors: G. Prestopino, M. Marinelli, E. Milani, C. Verona, G. Verona-Rinati P. Traina, E. Moreva, I. P. Degiovanni, M. Genovese, S. Ditalia Tchernij, F. Picollo, P. Olivero, J. Forneris

Abstract: Diamond is a promising platform for the development of technological applications in quantum optics and photonics. The quest for color centers with optimal photo-physical properties has led in recent years to the search for novel impurity-related defects in this material. Here, we report on a systematic investigation of the photo-physical properties of two He-related (HR) emission lines at 535 nm… ▽ More Diamond is a promising platform for the development of technological applications in quantum optics and photonics. The quest for color centers with optimal photo-physical properties has led in recent years to the search for novel impurity-related defects in this material. Here, we report on a systematic investigation of the photo-physical properties of two He-related (HR) emission lines at 535 nm and 560 nm created in three different diamond substrates upon implantation with 1.3 MeV He+ ions and subsequent annealing. The spectral features of the HR centers were studied in an "optical grade" diamond substrate as a function of several physical parameters, namely the measurement temperature, the excitation wavelength and the intensity of external electric fields. The emission lifetimes of the 535 nm and 560 nm lines were also measured by means of time-gated photoluminescence measurements, yielding characteristic decay times of (29 +- 5) ns and (106 +- 10) ns, respectively. The Stark shifting of the HR centers under the application of an external electrical field was observed in a CVD diamond film equipped with buried graphitic electrodes, suggesting a lack of inversion symmetry in the defects' structure. Furthermore, the photoluminescence mapping under 405 nm excitation of a "detector grade" diamond sample implanted at a 1x1010 cm-2 He+ ion fluence enabled to identify the spectral features of both the HR emission lines from the same localized optical spots. The reported results provide a first insight towards the understanding of the structure of He-related defects in diamond and their possible utilization in practical applications △ Less

Submitted 29 August, 2017; originally announced August 2017.

Comments: 9 pages, 3 figures

Single-photon-emitting optical centers in diamond fabricated upon Sn implantation

Authors: S. Ditalia Tchernij, T. Herzig, J. Forneris, J. Küpper, S. Pezzagna, P. Traina, E. Moreva, I. P. Degiovanni, G. Brida, N. Skukan, M. Genovese, M. Jakšić, J. Meijer, P. Olivero

Abstract: The fabrication of luminescent defects in single-crystal diamond upon Sn implantation and annealing is reported. The relevant spectral features of the optical centers (emission peaks at 593.5 nm, 620.3 nm, 630.7 nm and 646.7 nm) are attributed to Sn-related defects through the correlation of their photoluminescence (PL) intensity with the implantation fluence. Single Sn-related defects were identi… ▽ More The fabrication of luminescent defects in single-crystal diamond upon Sn implantation and annealing is reported. The relevant spectral features of the optical centers (emission peaks at 593.5 nm, 620.3 nm, 630.7 nm and 646.7 nm) are attributed to Sn-related defects through the correlation of their photoluminescence (PL) intensity with the implantation fluence. Single Sn-related defects were identified and characterized through the acquisition of their second-order auto-correlation emission functions, by means of Hanbury-Brown-Twiss interferometry. The investigation of their single-photon emission regime as a function of excitation laser power revealed that Sn-related defects are based on three-level systems with a 6 ns radiative decay lifetime. In a fraction of the studied centers, the observation of a blinking PL emission is indicative of the existence of a dark state. Furthermore, absorption dependence from the polarization of the excitation radiation with about 45 percent contrast was measured. This work shed light on the existence of a new optical center associated with a group-IV impurity in diamond, with similar photo-physical properties to the already well-known Si-V and Ge-V emitters, thus providing results of interest from both the fundamental and applicative points of view. △ Less

Submitted 26 September, 2017; v1 submitted 4 August, 2017; originally announced August 2017.

Comments: 10 pages, 4 figures

Mapping the local spatial charge in defective diamond by means of NV sensors - A "self-diagnostic" concept

Authors: J. Forneris, S. Ditalia Tchernij, P. Traina, E. Moreva, N. Skukan, M. Jakšić, V. Grilj, L. Croin, G. Amato, I. P. Degiovanni, B. Naydenov, F. Jelezko, M. Genovese, P. Olivero

Abstract: Electrically-active defects have a significant impact on the performance of electronic devices based on wide band-gap materials such as diamond. This issue is ubiquitous in diamond science and technology, since the presence of charge traps in the active regions of different classes of diamond-based devices (detectors, power diodes, transistors) can significantly affect their performances, due to t… ▽ More Electrically-active defects have a significant impact on the performance of electronic devices based on wide band-gap materials such as diamond. This issue is ubiquitous in diamond science and technology, since the presence of charge traps in the active regions of different classes of diamond-based devices (detectors, power diodes, transistors) can significantly affect their performances, due to the formation of space charge, memory effects and the degradation of the electronic response associated with radiation damage. Among the most common defects in diamond, the nitrogen-vacancy (NV) center possesses unique spin properties which enable high-sensitivity field sensing at the nanoscale. Here we demonstrate that NV ensembles can be successfully exploited to perform a direct local mapping of the internal electric field distribution of a graphite-diamond-graphite junction exhibiting electrical properties dominated by trap- and space-charge-related conduction mechanisms. By performing optically-detected magnetic resonance measurements, we performed both punctual readout and spatial mapping of the electric field in the active region at different bias voltages. In this novel "self-diagnostic" approach, defect complexes represent not only the source of detrimental space charge effects, but also a unique tool to directly investigate them, by providing experimental evidences on the conduction mechanisms that in previous studies could only be indirectly inferred on the basis of conventional electrical and optical characterization. △ Less

Submitted 24 June, 2017; originally announced June 2017.

Journal ref: Phys. Rev. Applied 10, 014024 (2018)

Formation of buried conductive micro-channels in single crystal diamond with MeV C and He implantation

Authors: F. Picollo, P. Olivero, F. Bellotti, Ž. Pastuović, N. Skukan, A. Lo Giudice, G. Amato, M. Jakšić, E. Vittone

Abstract: As demonstrated in previous works, implantation with a MeV ion microbeam through masks with graded thickness allows the formation of conductive micro-channels in diamond which are embedded in the insulating matrix at controllable depths [P. Olivero et al., Diamond Relat. Mater. 18 (5-8), 870-876 (2009)]. In the present work we report about the systematic electrical characterization of such micro-c… ▽ More As demonstrated in previous works, implantation with a MeV ion microbeam through masks with graded thickness allows the formation of conductive micro-channels in diamond which are embedded in the insulating matrix at controllable depths [P. Olivero et al., Diamond Relat. Mater. 18 (5-8), 870-876 (2009)]. In the present work we report about the systematic electrical characterization of such micro-channels as a function of several implantation conditions, namely: ion species and energy, implantation fluence. The current-voltage (IV) characteristics of the buried channels were measured at room temperature with a two point probe station. Significant parameters such as the sheet resistance and the characteristic exponent (alpha) of the IV power-law trend were expressed as a function of damage density, with satisfactory compatibility between the results obtained in different implantation conditions. △ Less

Submitted 9 September, 2016; originally announced September 2016.

Comments: 19 pages, 5 figures

Journal ref: Diamond and Related Materials 19 (5-6), 466-469 (2010)

Characterization of Three-Dimensional Microstructures in Single Crystal Diamond

Authors: P. Olivero, S. Rubanov, P. Reichart, B. C. Gibson, S. T. Huntington, J. R. Rabeau, A. D. Greentree, J. Salzman, D. Moore, D. N. Jamieson, S. Prawer

Abstract: We report on the Raman and photoluminescence characterization of three-dimensional microstructures created in single crystal diamond with a Focused Ion Beam (FIB) assisted lift-off technique. The method is based on MeV ion implantation to create a buried etchable layer, followed by FIB patterning and selective etching. In the applications of such microstructures where the properties of high qualit… ▽ More We report on the Raman and photoluminescence characterization of three-dimensional microstructures created in single crystal diamond with a Focused Ion Beam (FIB) assisted lift-off technique. The method is based on MeV ion implantation to create a buried etchable layer, followed by FIB patterning and selective etching. In the applications of such microstructures where the properties of high quality single crystal diamond are most relevant, residual damage after the fabrication process represents a critical technological issue. The results of Raman and photoluminescence characterization indicate that the partial distortion of the sp3-bonded lattice and the formation of isolated point defects are effectively removed after thermal annealing, leaving low amounts of residual damage in the final structures. Three-dimensional microstructures in single-crystal diamond offer a large range of applications, such as quantum optics devices and fully integrated opto mechanical assemblies. △ Less

Submitted 1 September, 2016; originally announced September 2016.

Comments: 30 pages, 7 figures

Journal ref: Diamond and Related Materials 15 (10), 1614 1621 (2006)

Micromachining structured optical fibers using focused ion beam milling

Authors: C. Martelli, P. Olivero, J. Canning, N. Groothoff, B. Gibson, S. Huntington

Abstract: A focused ion beam is used to mill side holes in air-silica structured fibres. By way of example, side holes are introduced in two types of air-structured fibres (1) a photonic crystal four-ring fibre and (2) a 6-hole single ring step index structured fibre. A focused ion beam is used to mill side holes in air-silica structured fibres. By way of example, side holes are introduced in two types of air-structured fibres (1) a photonic crystal four-ring fibre and (2) a 6-hole single ring step index structured fibre. △ Less

Submitted 1 September, 2016; originally announced September 2016.

Comments: 15 pages, 4 figures

Journal ref: Optics Letters 32 (11), 1575-1577 (2007)

Semiconductor characterization by scanning ion beam induced charge (IBIC) microscopy

Authors: E. Vittone, Z. Pastuovic, P. Olivero, C. Manfredotti, M. Jaksic, A. Lo Giudice, F. Fizzotti, E. Colombo

Abstract: The acronym IBIC (Ion Beam Induced Charge) was coined in early 1990's to indicate a scanning microscopy technique which uses MeV ion beams as probes to image the basic electronic properties of semiconductor materials and devices. Since then, IBIC has become a widespread analytical technique to characterize materials for electronics or for radiation detection, as testified by more than 200 papers p… ▽ More The acronym IBIC (Ion Beam Induced Charge) was coined in early 1990's to indicate a scanning microscopy technique which uses MeV ion beams as probes to image the basic electronic properties of semiconductor materials and devices. Since then, IBIC has become a widespread analytical technique to characterize materials for electronics or for radiation detection, as testified by more than 200 papers published so far in peer-reviewed journals. Its success stems from the valuable information IBIC can provide on charge transport phenomena occurring in finished devices, not easily obtainable by other analytical techniques. However, IBIC analysis requires a robust theoretical background to correctly interpret experimental data. In order to illustrate the importance of using a rigorous mathematical formalism, we present in this paper a benchmark IBIC experiment aimed to test the validity of the interpretative model based on the Gunn's theorem and to provide an example of the analytical capability of IBIC to characterize semiconductor devices. △ Less

Submitted 1 September, 2016; originally announced September 2016.

Comments: 22 pages, 7 figures

Journal ref: Nuclear Instruments and Methods in Physics Research B 266, 1312-1318 (2008)

Fabrication of Ultrathin Single-Crystal Diamond Membranes

Authors: B. A. Fairchild, P. Olivero, S. Rubanov, A. D. Greentree, F. Waldermann, R. A. Taylor, I. Walmsley, J. M. Smith, S. Huntington, B. C. Gibson, D. N. Jamieson, S. Prawer

Abstract: We demonstrate the fabrication of sub-micron layers of single-crystal diamond suitable for subsequent processing as demonstrated by this test ring structure. This method is a significant enabling technology for nanomechanical and photonic structures incorporating colour-centres. The process uses a novel double implant process, annealing and chemical etching to produce membranes of diamond from sin… ▽ More We demonstrate the fabrication of sub-micron layers of single-crystal diamond suitable for subsequent processing as demonstrated by this test ring structure. This method is a significant enabling technology for nanomechanical and photonic structures incorporating colour-centres. The process uses a novel double implant process, annealing and chemical etching to produce membranes of diamond from single-crystal starting material, the thinnest layers achieved to date are 210 nm thick. △ Less

Submitted 31 August, 2016; originally announced August 2016.

Comments: 21 pages, 4 figures

Journal ref: Advanced Materials 20 (24), 4793-4798 (2008)

Finite element analysis of ion-implanted diamond surface swelling

Authors: F. Bosia, P. Olivero, E. Vittone, F. Picollo, A. Lo Giudice, M. Jaksic, N. Skukan, L. Giuntini, M. Massi, S. Calusi, M. Vannoni, S. Lagomarsino, S. Sciortino

Abstract: We present experimental results and numerical Finite Element analysis to describe surface swelling due to the creation of buried graphite-like inclusions in diamond substrates subjected to MeV ion implantation. Numerical predictions are compared to experimental data for MeV proton and helium implantations, performed with scanning ion microbeams. Swelling values are measured with white light interf… ▽ More We present experimental results and numerical Finite Element analysis to describe surface swelling due to the creation of buried graphite-like inclusions in diamond substrates subjected to MeV ion implantation. Numerical predictions are compared to experimental data for MeV proton and helium implantations, performed with scanning ion microbeams. Swelling values are measured with white light interferometric profilometry in both cases. Simulations are based on a model which accounts for the through-the-thickness variation of mechanical parameters in the material, as a function of ion type, fluence and energy. Surface deformation profiles and internal stress distributions are analyzed and numerical results are seen to adequately fit experimental data. Results allow us to draw conclusions on structural damage mechanisms in diamond for different MeV ion implantations. △ Less

Submitted 29 August, 2016; originally announced August 2016.

Comments: 15 pages, 4 figures

Journal ref: Nuclear Instruments and Methods in Physics Research B 268, 2991-2995 (2010)

Direct fabrication of three-dimensional buried conductive channels in single crystal diamond with ion microbeam induced graphitization

Authors: P. Olivero, G. Amato, F. Bellotti, O. Budnyk, E. Colombo, M. Jaksic, A. Lo Giudice, C. Manfredotti, Z. Pastuovic, F. Picollo, N. Skukan, M. Vannoni, E. Vittone

Abstract: We report on a novel method for the fabrication of three-dimensional buried graphitic micropaths in single crystal diamond with the employment of focused MeV ions. The use of implantation masks with graded thickness at the sub-micrometer scale allows the formation of conductive channels which are embedded in the insulating matrix at controllable depths. In particular, the modulation of the channel… ▽ More We report on a novel method for the fabrication of three-dimensional buried graphitic micropaths in single crystal diamond with the employment of focused MeV ions. The use of implantation masks with graded thickness at the sub-micrometer scale allows the formation of conductive channels which are embedded in the insulating matrix at controllable depths. In particular, the modulation of the channels depth at their endpoints allows the surface contacting of the channel terminations with no need of further fabrication stages. In the present work we describe the sample masking, which includes the deposition of semi spherical gold contacts on the sample surface, followed by MeV ion implantation. Because of the significant difference between the densities of pristine and amorphous or graphitized diamond, the formation of buried channels has a relevant mechanical effect on the diamond structure, causing localized surface swelling, which has been measured both with interferometric profilometry and atomic force microscopy. The electrical properties of the buried channels are then measured with a two point probe station: clear evidence is given that only the terminal points of the channels are electrically connected with the surface, while the rest of the channels extends below the surface. IV measurements are employed also to qualitatively investigate the electrical properties of the channels as a function of implantation fluence and annealing. △ Less

Submitted 26 August, 2016; originally announced August 2016.

Comments: 27 pages, 10 figures

Journal ref: Diamond and Related Materials 18, 870-876 (2009)

Multitechnique characterization of lapis lazuli for provenance study

Authors: A. Lo Giudice, A. Re, S. Calusi, L. Giuntini, M. Massi, P. Olivero, G. Pratesi, M. Albonico, E. Conz

Abstract: Lapis Lazuli is one of the oldest precious stone, being used for glyptic as early as 7000 years ago: jewels, amulets, seals and inlays are examples of objects produced using this material. Only few sources of Lapis Lazuli exist in the world due to the low probability of geological conditions in which it can form, so that the possibility to associate the raw material to man-made objects helps to re… ▽ More Lapis Lazuli is one of the oldest precious stone, being used for glyptic as early as 7000 years ago: jewels, amulets, seals and inlays are examples of objects produced using this material. Only few sources of Lapis Lazuli exist in the world due to the low probability of geological conditions in which it can form, so that the possibility to associate the raw material to man-made objects helps to reconstruct trade routes. Since art objects produced using Lapis Lazuli are valuable, only non-destructive investigations can be carried out to identify the provenance of the raw materials. Ionoluminescence (IL) is a good candidate for this task. Similarly to cathodoluminescence (CL), IL consists in the collection of luminescence spectra induced by MeV ion (usually protons) irradiation. The main advantage of IL consists in the possibility of working in air while measuring simultaneously the composition of major and trace element by means of complementary Ion Beam Analysis techniques like PIXE or PIGE (Particle Induce X-ray or Gamma-ray Emission). In the present work a systematic study of the luminescence properties of Lapis Lazuli under charged particles irradiation is reported. In a first phase a multi-technique approach was adopted (CL, SEM with microanalysis, micro-Raman) to characterise luminescent minerals. This characterisation was propaedeutic for IL/PIXE/PIGE measurements carried out on significant areas selected on the basis of results obtained previously. Criteria to identify provenance of Lapis Lazuli from four of the main sources (Afghanistan, Pamir Mountains in Tajikistan, Chile and Siberia) were proposed. △ Less

Submitted 26 August, 2016; originally announced August 2016.

Comments: 9 pages, 5 figures

Journal ref: Analytical and Bioanalytical Chemistry 395 (7), 2211 2217 (2009)

Direct fabrication and IV characterization of sub-surface conductive channels in diamond with MeV ion implantation

Authors: P. Olivero, G. Amato, F. Bellotti, S. Borini, A. Lo Giudice, F. Picollo, E. Vittone

Abstract: In the present work we report about the investigation of the conduction mechanism of sp2 carbon micro-channels buried in single crystal diamond. The structures are fabricated with a novel technique which employs a MeV focused ion-beam to damage diamond in conjunction with variable thickness masks. This process changes significantly the structural proprieties of the target material, because the ion… ▽ More In the present work we report about the investigation of the conduction mechanism of sp2 carbon micro-channels buried in single crystal diamond. The structures are fabricated with a novel technique which employs a MeV focused ion-beam to damage diamond in conjunction with variable thickness masks. This process changes significantly the structural proprieties of the target material, because the ion nuclear energy loss induces carbon conversion from sp3 to sp2 state mainly at the end of range of the ions (few micrometers). Furthermore, placing a mask with increasing thickness on the sample it is possible to modulate the channels depth at their endpoints, allowing their electrical connection with the surface. A single-crystal HPHT diamond sample was implanted with 1.8 MeV He+ ions at room temperature, the implantation fluence was set in the range 2.1x10^16 - 6.3x10^17 ions cm^-2, determining the formation of buried micro-channels at 3 um. After deposition of metallic contacts at the channels' endpoints, the electrical characterization was performed measuring the I-V curves at variable temperatures in the 80-690 K range. The Variable Range Hopping model was used to fit the experimental data in the ohmic regime, allowing the estimation of characteristic parameters such as the density of localized states at the Fermi level. A value of 5.5x10^17 states cm-3 eV-1 was obtained, in satisfactory agreement with values previously reported in literature. The power-law dependence between current and voltage is consistent with the space charge limited mechanism at moderate electric fields. △ Less

Submitted 26 August, 2016; originally announced August 2016.

Comments: 17 pages, 8 figures

Journal ref: The European Physical Journal B 75 (2), 127 132 (2010)

Controlled variation of the refractive index in ion-damaged diamond

Authors: P. Olivero, S. Calusi, L. Giuntini, S. Lagomarsino, A. Lo Giudice, M. Massi, S. Sciortino, M. Vannoni, E. Vittone

Abstract: A fine control of the variation of the refractive index as a function of structural damage is essential in the fabrication of diamond-based optical and photonic devices. We report here about the variation of the real part of the refractive index at lambda=632.8 nm in high quality single crystal diamond damaged with 2 and 3 MeV protons at low-medium fluences (10^13 - 10^17 ions cm^-2). After implan… ▽ More A fine control of the variation of the refractive index as a function of structural damage is essential in the fabrication of diamond-based optical and photonic devices. We report here about the variation of the real part of the refractive index at lambda=632.8 nm in high quality single crystal diamond damaged with 2 and 3 MeV protons at low-medium fluences (10^13 - 10^17 ions cm^-2). After implanting the samples in 125x125 um^2 areas with a raster scanning ion microbeam, the variation of optical thickness of the implanted regions was measured with laser interferometric microscopy. The results were analyzed with a model based on the specific damage profile. The technique allows the direct fabrication of optical structures in bulk diamond based on the localized variation of the refractive index, which will be explored in future works. △ Less

Submitted 26 August, 2016; originally announced August 2016.

Comments: 15 pages, 4 figures

Journal ref: Diamond and Related Materials 19 (5-6), 428-431 (2010)

Raman spectroscopic features of the neutral vacancy in diamond from ab initio quantum-mechanical calculations

Authors: J. Baima, A. Zelferino, P. Olivero, A. Erba, R. Dovesi

Abstract: Quantum-mechanical ab initio calculations are performed to elucidate the vibrational spectroscopic features of a common irradiation-induced defect in diamond, i.e. the neutral vacancy. Raman spectra are computed analytically through a Coupled-Perturbed-Hartree-Fock/Kohn-Sham approach as a function of both different defect spin states and defect concentration. The experimental Raman features of def… ▽ More Quantum-mechanical ab initio calculations are performed to elucidate the vibrational spectroscopic features of a common irradiation-induced defect in diamond, i.e. the neutral vacancy. Raman spectra are computed analytically through a Coupled-Perturbed-Hartree-Fock/Kohn-Sham approach as a function of both different defect spin states and defect concentration. The experimental Raman features of defective diamond located in the 400-1300 cm-1 spectral range, i.e. below the first-order line of pristine diamond at 1332 cm-1 , are well reproduced, thus corroborating the picture according to which, at low damage densities, this spectral region is mostly affected by non-graphitic sp3 defects. No peaks above 1332 cm-1 are found, thus ruling out previous tentative assignments of different spectral features (at 1450 and 1490 cm-1) to the neutral vacancy. The perturbation introduced by the vacancy to the thermal nuclear motion of carbon atoms in the defective lattice is discussed in terms of atomic anisotropic displacement parameters (ADPs), computed from converged lattice dynamics calculations. △ Less

Submitted 26 August, 2016; originally announced August 2016.

Comments: 8 pages, 5 figures, 1 table

Journal ref: Physical Chemistry Chemical Physics 18, 1961-1968 (2016)

Luminescence centers in proton irradiated single crystal CVD diamond

Authors: C. Manfredotti, S. Calusi, A. Lo Giudice, L. Giuntini, M. Massi, P. Olivero, A. Re

Abstract: Diamond displays a large variety of luminescence centers which define its optical properties and can be either created or modified by irradiation. The main purpose of the present work is to study the radiation hardness of several of such centers in homoepitaxial single crystal CVD diamond by following the evolution of photoluminescence and ionoluminescence upon 2 MeV proton irradiation. Luminescen… ▽ More Diamond displays a large variety of luminescence centers which define its optical properties and can be either created or modified by irradiation. The main purpose of the present work is to study the radiation hardness of several of such centers in homoepitaxial single crystal CVD diamond by following the evolution of photoluminescence and ionoluminescence upon 2 MeV proton irradiation. Luminescence decays were observed with values of the fluence at half of the starting luminescence (F1/2) of the order of 1014 cm-2. The 3H center displayed a non monotonic behavior, with a growing behavior and a subsequent decay with a rather high F1/2 value (in the order of few 1016 cm-2), maintaining at the highest fluences an intensity significantly higher than the blue A-band. A simple model based on a double-exponential trend was defined to fit with satisfactory accuracy the evolution of the 3H center. Several PL centers (namely: 3H, TR12, 491 nm, 494 nm) exhibited clear correlations and anti-correlations in their fluence dependences, which were considered in the attempt to acquire some insight into their possible alternative attributions. △ Less

Submitted 25 August, 2016; originally announced August 2016.

Comments: 20 pages, 7 figures

Journal ref: Diamond and Related Materials 19, 854-860 (2010)

Modification of the structure of diamond with MeV ion implantation

Authors: F. Bosia, N. Argiolas, M. Bazzan, P. Olivero, F. Picollo, A. Sordini, M. Vannoni, E. Vittone

Abstract: We present experimental results and numerical simulations to investigate the modification of structural-mechanical properties of ion-implanted single-crystal diamond. A phenomenological model is used to derive an analytical expression for the variation of mass density and elastic properties as a function of damage density in the crystal. These relations are applied together with SRIM Monte Carlo s… ▽ More We present experimental results and numerical simulations to investigate the modification of structural-mechanical properties of ion-implanted single-crystal diamond. A phenomenological model is used to derive an analytical expression for the variation of mass density and elastic properties as a function of damage density in the crystal. These relations are applied together with SRIM Monte Carlo simulations to set up Finite Element simulations for the determination of internal strains and surface deformation of MeV-ion-implanted diamond samples. The results are validated through comparison with high resolution X-ray diffraction and white-light interferometric profilometry experiments. The former are carried out on 180 keV B implanted diamond samples, to determine the induced structural variation, in terms of lattice spacing and disorder, whilst the latter are performed on 1.8 MeV He implanted diamond samples to measure surface swelling. The effect of thermal processing on the evolution of the structural-mechanical properties of damaged diamond is also evaluated by performing the same profilometric measurements after annealing at 1000 °C, and modeling the obtained trends with a suitably modified analytical model. The results allow the development of a coherent model describing the effects of MeV-ion-induced damage on the structural-mechanical properties of single-crystal diamond. In particular, we suggest a more reliable method to determine the so-called diamond "graphitization threshold" for the considered implantation type. △ Less

Submitted 25 August, 2016; originally announced August 2016.

Comments: 19 pages, 4 figures

Journal ref: Diamond and Related Materials 20, 774-778 (2011)

Ultra-smooth single crystal diamond surfaces resulting from implantation and lift-off processes

Authors: T. N. Tran Thi, B. Fernandez, D. Eon, E. Gheeraert, J. Hartwig, T. A. Lafford, A. Perrat-Mabilon, C. Peaucelle, P. Olivero, E. Bustarret

Abstract: A method for obtaining a smooth, single crystal diamond surface is presented, whereby a sacrificial defective layer is created by implantation and graphitized by annealing before being selectively etched. We have used O+ at 240 keV, the main process variables being the ion fluence (ranging from 3x10^15 cm^-2 to 3x10^17 cm^-2) and the final etching process (wet etch, H2 plasma and annealing in air)… ▽ More A method for obtaining a smooth, single crystal diamond surface is presented, whereby a sacrificial defective layer is created by implantation and graphitized by annealing before being selectively etched. We have used O+ at 240 keV, the main process variables being the ion fluence (ranging from 3x10^15 cm^-2 to 3x10^17 cm^-2) and the final etching process (wet etch, H2 plasma and annealing in air). The substrates were characterized by atomic force microscopy, optical profilometry and white beam X-ray topography. The influence of the various process parameters on the resulting lift-off efficiency and final surface roughness is discussed. An O+ fluence of 2x10^17 cm^-2 was found to result in sub-nanometre roughness over tens of um^2. △ Less

Submitted 25 August, 2016; originally announced August 2016.

Comments: 4 pages, 4 figures

Journal ref: Physica Status Solidi A 208 (9), 2057-2061 (2011)

An upper limit on the lateral vacancy diffusion length in diamond

Authors: J. O. Orwa, K. Ganesan, J. Newnham, C. Santori, P. Barclay, K. M. C. Fu, R. G. Beausoleil, I. Aharonovich, B. A. Fairchild, P. Olivero, A. D. Greentree, S. Prawer

Abstract: Ion implantation is widely used to modify the structural, electrical and optical properties of materials. By appropriate masking, this technique can be used to define nano- and micro-structures. However, depending on the type of mask used, experiments have shown that vacancy-related substrate modification can be inferred tens of microns away from the edge of the mask used to define the implanted r… ▽ More Ion implantation is widely used to modify the structural, electrical and optical properties of materials. By appropriate masking, this technique can be used to define nano- and micro-structures. However, depending on the type of mask used, experiments have shown that vacancy-related substrate modification can be inferred tens of microns away from the edge of the mask used to define the implanted region. This could be due to fast diffusion of vacancies from the implanted area during annealing or to a geometric effect related to ion scattering around the mask edges. For quantum and single-atom devices, stray ion damage can be deleterious and must be minimized. In order to profile the distribution of implantation-induced damage, we have used the nitrogen-vacancy colour centre as a sensitive marker for vacancy concentration and distribution following MeV He ion implantation into diamond and annealing. Results show that helium atoms implanted through a mask clamped to the diamond surface are scattered underneath the mask to distances in the range of tens of micrometers from the mask edge. Implantation through a lithographically defined and deposited mask, with no spacing between the mask and the substrate, significantly reduces the scattering to <5 m but does not eliminate it. These scattering distances are much larger than the theoretically estimated vacancy diffusion distance of 260 nm under similar conditions. This paper shows that diffusion, upon annealing, of vacancies created by ion implantation in diamond is limited and the appearance of vacancies many tens of micrometers from the edge of the mask is due to scattering effects. △ Less

Submitted 25 August, 2016; originally announced August 2016.

Comments: 21 pages, 4 figures

Journal ref: Diamond and Related Materials 24, 6-10 (2012)

Complex refractive index variation in proton-damaged diamond

Authors: S. Lagomarsino, P. Olivero, S. Calusi, D. Gatto Monticone, L. Giuntini, M. Massi, S. Sciortino, A. Sytchkova, A. Sordini, M. Vannoni

Abstract: An accurate control of the optical properties of single crystal diamond during microfabrication processes such as ion implantation plays a crucial role in the engineering of integrated photonic devices. In this work we present a systematic study of the variation of both real and imaginary parts of the refractive index of single crystal diamond, when damaged with 2 and 3 MeV protons at low-medium f… ▽ More An accurate control of the optical properties of single crystal diamond during microfabrication processes such as ion implantation plays a crucial role in the engineering of integrated photonic devices. In this work we present a systematic study of the variation of both real and imaginary parts of the refractive index of single crystal diamond, when damaged with 2 and 3 MeV protons at low-medium fluences (range: 10^15 - 10^17 cm^-2). After implanting in 125x125 um^2 areas with a scanning ion microbeam, the variation of optical pathlength of the implanted regions was measured with laser interferometric microscopy, while their optical transmission was studied using a spectrometric set-up with micrometric spatial resolution. On the basis of a model taking into account the strongly non-uniform damage profile in the bulk sample, the variation of the complex refractive index as a function of damage density was evaluated. △ Less

Submitted 25 August, 2016; originally announced August 2016.

Comments: 13 pages, 7 figures. arXiv admin note: text overlap with arXiv:1608.07122

Journal ref: Optics Express 20 (17), 19382-19394 (2012)

A 3-dimensional interdigitated electrode geometry for the enhancement of charge collection efficiency in diamond detectors

Authors: J. Forneris, A. Lo Giudice, P. Olivero, F. Picollo, A. Re, M. Marinelli, F. Pompili, C. Verona, G. Verona Rinati, M. Benetti, D. Cannata, F. Di Pietrantonio

Abstract: In this work, a single crystal CVD diamond film with a novel three-dimensional (3D) interdigitated electrode geometry has been fabricated with the Reactive Ion Etching (RIE) technique in order to increase the charge collection efficiency (CCE) with respect to that obtained by standard superficial electrodes. The geometrical arrangement of the electric field lines due to the 3D patterning of the el… ▽ More In this work, a single crystal CVD diamond film with a novel three-dimensional (3D) interdigitated electrode geometry has been fabricated with the Reactive Ion Etching (RIE) technique in order to increase the charge collection efficiency (CCE) with respect to that obtained by standard superficial electrodes. The geometrical arrangement of the electric field lines due to the 3D patterning of the electrodes results in a shorter travel path for the excess charge carriers, thus contributing to a more efficient charge collection mech-anism. The CCE of the device was mapped by means of the Ion Beam Induced Charge (IBIC) technique. A 1 MeV proton micro-beam was raster scanned over the active area of the diamond detector under different bias voltage conditions, enabling to probe the charge transport properties of the detector up to a depth of 8 μm below the sample surface. The experimental results, supported by the numerical simulations, show a significant improvement in the 3D-detector performance (i.e. CCE, energy resolution, extension of the active area) if compared with the results obtained by standard surface metallic electrodes. △ Less

Submitted 25 August, 2016; originally announced August 2016.

Comments: 5 pages, 4 figures

Journal ref: Europhysics Letters 108, 18001 (2014)

Single-photon emitters based on NIR colour centres in diamond coupled with solid immersion lenses

Authors: D. Gatto Monticone, J. Forneris, M. Levi, A. Battiato, F. Picollo, P. Olivero, P. Traina, E. Moreva, E. Enrico, G. Brida, I. P. Degiovanni, M. Genovese, G. Amato, L. Boarino

Abstract: Single-photon sources represent a key enabling technology in quantum optics, and single colour centres in diamond are a promising platform to serve this purpose, due to their high quantum efficiency and photostability at room temperature. The widely studied nitrogen vacancy centres are characterized by several limitations, thus other defects have recently been considered, with a specific focus of… ▽ More Single-photon sources represent a key enabling technology in quantum optics, and single colour centres in diamond are a promising platform to serve this purpose, due to their high quantum efficiency and photostability at room temperature. The widely studied nitrogen vacancy centres are characterized by several limitations, thus other defects have recently been considered, with a specific focus of centres emitting in the Near Infra-Red. In the present work, we report on the coupling of native near-infrared-emitting centres in high-quality single crystal diamond with Solid Immersion Lens structures fabricated by Focused Ion Beam lithography. The reported improvements in terms of light collection efficiency make the proposed system an ideal platform for the development of single-photon emitters with appealing photophysical and spectral properties. △ Less

Submitted 25 August, 2016; originally announced August 2016.

Comments: 17 pages, 5 figures

Journal ref: International Journal of Quantum Information 12 (7-8), 1560011 (2014)

Kelvin probe characterization of buried graphitic microchannels in single-crystal diamond

Authors: E. Bernardi, A. Battiato, P. Olivero, F. Picollo, E. Vittone

Abstract: In this work, we present an investigation by Kelvin Probe Microscopy (KPM) of buried graphitic microchannels fabricated in single-crystal diamond by direct MeV ion microbeam writing. Metal deposition of variable-thickness masks was adopted to implant channels with emerging endpoints and high temperature annealing was performed in order to induce the graphitization of the highly-damaged buried regi… ▽ More In this work, we present an investigation by Kelvin Probe Microscopy (KPM) of buried graphitic microchannels fabricated in single-crystal diamond by direct MeV ion microbeam writing. Metal deposition of variable-thickness masks was adopted to implant channels with emerging endpoints and high temperature annealing was performed in order to induce the graphitization of the highly-damaged buried region. When an electrical current was flowing through the biased buried channel, the structure was clearly evidenced by KPM maps of the electrical potential of the surface region overlying the channel at increasing distances from the grounded electrode. The KPM profiling shows regions of opposite contrast located at different distances from the endpoints of the channel. This effect is attributed to the different electrical conduction properties of the surface and of the buried graphitic layer. The model adopted to interpret these KPM maps and profiles proved to be suitable for the electronic characterization of buried conductive channels, providing a non-invasive method to measure the local resistivity with a micrometer resolution. The results demonstrate the potential of the technique as a powerful diagnostic tool to monitor the functionality of all-carbon graphite/diamond devices to be fabricated by MeV ion beam lithography. △ Less

Submitted 25 August, 2016; originally announced August 2016.

Comments: 21 pages, 5 figures

Journal ref: Journal of Applied Physics 117, 024103 (2015)

Micro-beam and pulsed laser beam techniques for the micro-fabrication of diamond surface and bulk structures

Authors: S. Sciortino, M. Bellini, F. Bosia, S. Calusi, C. Corsi, C. Czelusniak, N. Gelli, L. Giuntini, F. Gorelli, S. Lagomarsino, P. A. Mando, M. Massi, P. Olivero, G. Parrini, M. Santoro, A. Sordini, A. Sytchkova, F. Taccetti, M. Vannoni

Abstract: Micro-fabrication in diamond is involved in a wide set of emerging technologies, exploiting the exceptional characteristics of diamond for application in bio-physics, photonics, radiation detection. Micro ion-beam irradiation and pulsed laser irradiation are complementary techniques, which permit the implementation of complex geometries, by modification and functionalization of surface and/or bulk… ▽ More Micro-fabrication in diamond is involved in a wide set of emerging technologies, exploiting the exceptional characteristics of diamond for application in bio-physics, photonics, radiation detection. Micro ion-beam irradiation and pulsed laser irradiation are complementary techniques, which permit the implementation of complex geometries, by modification and functionalization of surface and/or bulk material, modifying the optical, electrical and mechanical characteristics of the material. In this article we summarize the work done in Florence (Italy) concerning ion beam and pulsed laser beam micro-fabrication in diamond. △ Less

Submitted 25 August, 2016; originally announced August 2016.

Comments: 14 pages, 5 figures

Journal ref: Nuclear Instruments and Methods in Physics Research B 348, 191 198 (2015)

Structural transformation of implanted diamond layers during high temperature annealing

Authors: S. Rubanov, B. A. Fairchild, A. Suvorova, P. Olivero, S. Prawer

Abstract: In the recent years graphitization of ion-beam induced amorphous layers became the basic tool for device fabrication in diamond. The etchable graphitic layers can be removed to form free-standing membranes into which the desired structures can be sculpted using FIB milling. The optical properties of the devices fabricated using this method are assumed on the model of sharp diamond-air interface. T… ▽ More In the recent years graphitization of ion-beam induced amorphous layers became the basic tool for device fabrication in diamond. The etchable graphitic layers can be removed to form free-standing membranes into which the desired structures can be sculpted using FIB milling. The optical properties of the devices fabricated using this method are assumed on the model of sharp diamond-air interface. The real quality of this interface could depend on degree of graphitization of the amorphous damage layers after annealing. In the present work the graphitization process was studied using conventional and analytical TEM. It was found that annealing at 550 °C results in a partial graphitization of the implanted volume with formation of the nano-crystalline graphitic phase sandwiched between layers of tetrahedral amorphous carbon. Annealing at 1400 °C resulted in complete graphitization of the amorphous layers. The average size of graphite nano-crystals did not exceed 5 nm with predominant orientation of c-planes normal to the sample surface. △ Less

Submitted 25 August, 2016; originally announced August 2016.

Comments: 10 pages, 4 figures

Journal ref: Nuclear Instruments and Methods in Physics Research B 365A, 50-54 (2015)

Effects of high-power laser irradiation on sub-superficial graphitic layers in single crystal diamond

Authors: F. Picollo, S. Rubanov, C. Tomba, A. Battiato, E. Enrico, A. Perrat-Mabilon, C. Peaucelle, T. N. Tran Thi, L. Boarino, E. Gheeraert, P. Olivero

Abstract: We report on the structural modifications induced by a lambda = 532 nm ns-pulsed high-power laser on sub-superficial graphitic layers in single-crystal diamond realized by means of MeV ion implantation. A systematic characterization of the structures obtained under different laser irradiation conditions (power density, number of pulses) and subsequent thermal annealing was performed by different e… ▽ More We report on the structural modifications induced by a lambda = 532 nm ns-pulsed high-power laser on sub-superficial graphitic layers in single-crystal diamond realized by means of MeV ion implantation. A systematic characterization of the structures obtained under different laser irradiation conditions (power density, number of pulses) and subsequent thermal annealing was performed by different electron microscopy techniques. The main feature observed after laser irradiation is the thickening of the pre-existing graphitic layer. Cross sectional SEM imaging was performed to directly measure the thickness of the modified layers, and subsequent selective etching of the buried layers was employed to both assess their graphitic nature and enhance the SEM imaging contrast. In particular, it was found that for optimal irradiation parameters the laser processing induces a six-fold increase the thickness of sub superficial graphitic layers without inducing mechanical failures in the surrounding crystal. TEM microscopy and EELS spectroscopy allowed a detailed analysis of the internal structure of the laser irradiated layers, highlighting the presence of different nano graphitic and amorphous layers. The obtained results demonstrate the effectiveness and versatility of high-power laser irradiation for an accurate tuning of the geometrical and structural features of graphitic structures embedded in single crystal diamond, and open new opportunities in diamond fabrication. △ Less

Submitted 25 August, 2016; originally announced August 2016.

Comments: 24 pages, 7 figures

Journal ref: Acta Materialia 103, 665-671 (2016)

Characterization of the recovery of mechanical properties of ion-implanted diamond after thermal annealing

Authors: M. Mohr, F. Picollo, A. Battiato, E. Bernardi, J. Forneris, A. Tengattini, E. Enrico, L. Boarino, F. Bosia, H. J. Fecht, P. Olivero

Abstract: Due to their outstanding mechanical properties, diamond and diamond-like materials find significant technological applications ranging from well-established industrial fields (cutting tools, coatings, etc.) to more advanced mechanical devices as micro- and nano-electromechanical systems. The use of energetic ions is a powerful and versatile tool to fabricate three-dimensional micro-mechanical stru… ▽ More Due to their outstanding mechanical properties, diamond and diamond-like materials find significant technological applications ranging from well-established industrial fields (cutting tools, coatings, etc.) to more advanced mechanical devices as micro- and nano-electromechanical systems. The use of energetic ions is a powerful and versatile tool to fabricate three-dimensional micro-mechanical structures. In this context, it is of paramount importance to have an accurate knowledge of the effects of ion-induced structural damage on the mechanical properties of this material, firstly to predict potential undesired side-effects of the ion implantation process, and possibly to tailor the desired mechanical properties of the fabricated devices. We present an Atomic Force Microscopy (AFM) characterization of free-standing cantilevers in single-crystal diamond obtained by a FIB-assisted lift-off technique, which allows a determination of the Young's modulus of the diamond crystal after the MeV ion irradiation process concurrent to the fabrication of the microstructures, and subsequent thermal annealing. The AFM measurements were performed with the beam-bending technique and show that the thermal annealing process allows for an effective recovery of the mechanical properties of the pristine crystal. △ Less

Submitted 25 August, 2016; originally announced August 2016.

Comments: 15 pages, 5 figures

Journal ref: Diamond and Related Materials 63, 75-79 (2016)

Softening the ultra-stiff: controlled variation of Young's modulus in single crystal diamond

Authors: A. Battiato, M. Lorusso, E. Bernardi, F. Picollo, F. Bosia, D. Ugues, A. Zelferino, A. Damin, J. Baima, N. M. Pugno, E. P. Ambrosio, P. Olivero

Abstract: A combined experimental and numerical study on the variation of the elastic properties of defective single-crystal diamond is presented for the first time, by comparing nano-indentation measurements on MeV-ion-implanted samples with multi-scale modeling consisting of both ab initio atomistic calculations and meso-scale Finite Element Method (FEM) simulations. It is found that by locally introducin… ▽ More A combined experimental and numerical study on the variation of the elastic properties of defective single-crystal diamond is presented for the first time, by comparing nano-indentation measurements on MeV-ion-implanted samples with multi-scale modeling consisting of both ab initio atomistic calculations and meso-scale Finite Element Method (FEM) simulations. It is found that by locally introducing defects in the 2x10^18 - 5x10^21 cm-3 density range, a significant reduction of, as well as of density, can be induced in the diamond crystal structure without incurring in the graphitization of the material. Ab initio atomistic simulations confirm the experimental findings with a good degree of confidence. FEM simulations are further employed to verify the consistency of measured deformations with a stiffness reduction, and to derive strain and stress levels in the implanted region. Combining these experimental and numerical results, we also provide insight into the mechanism responsible for the depth dependence of the graphitization threshold in diamond. This work prospects the possibility of achieving accurate tunability of the mechanical properties of single-crystal diamond through defect engineering, with significant technological applications, i.e. the fabrication and control of the resonant frequency of diamond-based micromechanical resonators. △ Less

Submitted 25 August, 2016; originally announced August 2016.

Comments: 32 pages, 7 figures

Journal ref: Acta Materialia 116, 95-103 (2016)

Micro and nano-patterning of single-crystal diamond by swift heavy ion irradiation

Authors: G. Garcia, I. Preda, M. Diaz-Hijar, V. Tormo-Marquez, O. Pena Rodriguez, J. Olivares, F. Bosia, N. M. Pugno, F. Picollo, L. Giuntini, A. Sordini, P. Olivero, L. Lopez-Mir, C. Ocal

Abstract: This paper presents experimental data and analysis of the structural damage caused by swift-heavy ion irradiation of single-crystal diamond. The patterned buried structural damage is shown to generate, via swelling, a mirror-pattern on the sample surface, which remains largely damage-free. While extensive results are available for light ion implantations, this effect is reported here for the first… ▽ More This paper presents experimental data and analysis of the structural damage caused by swift-heavy ion irradiation of single-crystal diamond. The patterned buried structural damage is shown to generate, via swelling, a mirror-pattern on the sample surface, which remains largely damage-free. While extensive results are available for light ion implantations, this effect is reported here for the first time in the heavy ion regime, where a completely different range of input parameters (in terms of ion species, energy, stopping power, etc.) is available for customized irradiation. The chosen ion species are Au and Br, in the energy range 10-40 MeV. The observed patterns, as characterized by profilometry and atomic force microscopy, are reported in a series of model experiments, which show swelling patterns ranging from a few nm to above 200 nm. Moreover, a systematic phenomenological modelling is presented, in which surface swelling measurements are correlated to buried crystal damage. A comparison is made with data for light ion implantations, showing good compatibility with the proposed models. The modelling presented in this work can be useful for the design and realization of micropatterned surfaces in single crystal diamond, allowing to generate highly customized structures by combining appropriately chosen irradiation parameters and masks. △ Less

Submitted 25 August, 2016; originally announced August 2016.

Comments: 20 pages, 8 figures

Journal ref: Diamond and Related Materials 69, 1 (2016)

Electrical control of deep NV centers in diamond by means of sub-superficial graphitic micro-electrodes

Authors: J. Forneris, S. Ditalia Tchernij, A. Tengattini, E. Enrico, V. Grilj, N. Skukan, G. Amato, L. Boarino, M. Jakšić, P. Olivero

Abstract: The control of the charge state of nitrogen-vacancy (NV) centers in diamond is of primary importance for the stabilization of their quantum-optical properties, in applications ranging from quantum sensing to quantum computing. To this purpose, in this work current-injecting micro-electrodes were fabricated in bulk diamond for NV charge state control. Buried (i.e. 3 μm in depth) graphitic micro-ele… ▽ More The control of the charge state of nitrogen-vacancy (NV) centers in diamond is of primary importance for the stabilization of their quantum-optical properties, in applications ranging from quantum sensing to quantum computing. To this purpose, in this work current-injecting micro-electrodes were fabricated in bulk diamond for NV charge state control. Buried (i.e. 3 μm in depth) graphitic micro-electrodes with spacing of 9 μm were created in single-crystal diamond substrates by means of a 6 MeV C scanning micro-beam. The high breakdown field of diamond was exploited to electrically control the variation in the relative population of the negative (NV-) and neutral (NV0) charge states of sub-superficial NV centers located in the inter- electrode gap regions, without incurring into current discharges. Photoluminescence spectra acquired from the biased electrodes exhibited an electrically induced increase up to 40% in the NV- population at the expense of the NV0 charge state. The variation in the relative charge state populations showed a linear dependence from the injected current at applied biases smaller than 250 V, and was interpreted as the result of electron trapping at NV sites, consistently with the Space Charge Limited Current interpretation of the abrupt current increase observed at 300 V bias voltage. In correspondence of such trap-filling-induced transition to a high-current regime, a strong electroluminescent emission from the NV0 centers was observed. In the high-current-injection regime, a decrease in the NV- population was observed, in contrast with the results obtained at lower bias voltages. These results disclose new possibilities in the electrical control of the charge state of NV centers located in the diamond bulk, which are characterized by longer spin coherence times. △ Less

Submitted 19 July, 2016; originally announced July 2016.

Comments: 28 pages, 8 figures

Creation and characterization of He-related color centers in diamond

Authors: Jacopo Forneris, Andrea Tengattini, Sviatoslav Ditalia Tchernij, Federico Picollo, Alfio Battiato, Paolo Traina, Ivo Degiovanni, Ekaterina Moreva, Giorgio Brida, Veljko Grilj, Natko Skukan, Milko Jakšić, Marco Genovese, Paolo Olivero

Abstract: Diamond is a promising material for the development of emerging applications in quantum optics, quantum information and quantum sensing. The fabrication and characterization of novel luminescent defects with suitable opto-physical properties is therefore of primary importance for further advances in these research fields. In this work we report on the investigation in the formation of photolumines… ▽ More Diamond is a promising material for the development of emerging applications in quantum optics, quantum information and quantum sensing. The fabrication and characterization of novel luminescent defects with suitable opto-physical properties is therefore of primary importance for further advances in these research fields. In this work we report on the investigation in the formation of photoluminescent (PL) defects upon MeV He implantation in diamond. Such color centers, previously reported only in electroluminescence and cathodoluminescence regime, exhibited two sharp emission lines at 536.5 nm and 560.5 nm, without significant phonon sidebands. A strong correlation between the PL intensities of the above-mentioned emission lines and the He implantation fluence was found in the 10^15-10^17 cm^{-2} fluence range. The PL emission features were not detected in control samples, i.e. samples that were either unirradiated or irradiated with different ion species (H, C). Moreover, the PL emission lines disappeared in samples that were He-implanted above the graphitization threshold. Therefore, the PL features are attributed to optically active defects in the diamond matrix associated with He impurities. The intensity of the 536.5 nm and 560.5 nm emission lines was investigated as a function of the annealing temperature of the diamond substrate. The emission was observed upon annealing at temperatures higher than 500°C, at the expenses of the concurrently decreasing neutral-vacancy-related GR1 emission intensity. Therefore, our findings indicate that the luminescence originates from the formation of a stable lattice defect. Finally, the emission was investigated under different laser excitations wavelengths (i.e. 532 nm and 405 nm) with the purpose of gaining a preliminary insight about the position of the related levels in the energy gap of diamond. △ Less

Submitted 4 June, 2016; originally announced June 2016.

Journal ref: Journal of Luminescence 179 (2016) 59-63

Electroluminescence from nitrogen-vacancy and interstitial-related centers in bulk diamond stimulated by ion-beam-fabricated sub-superficial graphitic micro-electrodes

Authors: J. Forneris, S. Ditalia Tchernij, A. Battiato, F. Picollo, A. Tengattini, V. Grilj, N. Skukan, G. Amato, L. Boarino, I. P. Degiovanni, E. Enrico, P. Traina, M. Jakšić, M. Genovese, P. Olivero

Abstract: We report on the fabrication and characterization of a single-crystal diamond device for the electrical stimula- tion of light emission from nitrogen-vacancy (NV0) and other defect-related centers. Pairs of sub-superficial graphitic micro-electrodes embedded in insulating diamond were fabricated by a 6 MeV C3+ micro-beam irra- diation followed by thermal annealing. A photoluminescence (PL) charact… ▽ More We report on the fabrication and characterization of a single-crystal diamond device for the electrical stimula- tion of light emission from nitrogen-vacancy (NV0) and other defect-related centers. Pairs of sub-superficial graphitic micro-electrodes embedded in insulating diamond were fabricated by a 6 MeV C3+ micro-beam irra- diation followed by thermal annealing. A photoluminescence (PL) characterization evidenced a low radiation damage concentration in the inter-electrode gap region, which did not significantly affect the PL features domi- nated by NV centers. The operation of the device in electroluminescence (EL) regime was investigated by ap- plying a bias voltage at the graphitic electrodes, resulting in the injection of a high excitation current above a threshold voltage (~300V), which effectively stimulated an intense EL emission from NV0 centers. In addition, we report on the new observation of two additional sharp EL emission lines (at 563 nm and 580 nm) related to interstitial defects formed during MeV ion beam fabrication. △ Less

Submitted 8 July, 2015; originally announced July 2015.

An analytical model for the mechanical deformation of locally graphitized diamond

Authors: Marco Piccardo, Federico Bosia, Paolo Olivero, Nicola Pugno

Abstract: We propose an analytical model to describe the mechanical deformation of single-crystal diamond following the local sub-superficial graphitization obtained by laser beams or MeV ion microbeam implantation. In this case, a local mass-density variation is generated at specific depths within the irradiated micrometric regions, which in turn leads to swelling effects and the development of correspondi… ▽ More We propose an analytical model to describe the mechanical deformation of single-crystal diamond following the local sub-superficial graphitization obtained by laser beams or MeV ion microbeam implantation. In this case, a local mass-density variation is generated at specific depths within the irradiated micrometric regions, which in turn leads to swelling effects and the development of corresponding mechanical stresses. Our model describes the constrained expansion of the locally damaged material and correctly predicts the surface deformation, as verified by comparing analytical results with experimental profilometry data and Finite Element simulations. The model can be adopted to easily evaluate the stress and strain fields in locally graphitized diamond in the design of microfabrication processes involving the use of focused ion/laser beams, for example to predict the potential formation of cracks, or to evaluate the influence of stress on the properties of opto mechanical devices. △ Less

Submitted 11 February, 2015; originally announced February 2015.

Comments: 29 pages, 7 figures

Journal ref: Diamond and Related Materials 48, 73-81 (2014)

Realization of a diamond based high density multi electrode array by means of deep ion beam lithography

Authors: Federico Picollo, Alfio Battiato, Ettore Bernardi, Luca Boarino, Emanuele Enrico, Jacopo Forneris, Daniele Gatto Monticone, Paolo Olivero

Abstract: In the present work we report about a parallel-processing ion beam fabrication technique whereby high-density sub-superficial graphitic microstructures can be created in diamond. Ion beam implantation is an effective tool for the structural modification of diamond: in particular ion-damaged diamond can be converted into graphite, therefore obtaining an electrically conductive phase embedded in an… ▽ More In the present work we report about a parallel-processing ion beam fabrication technique whereby high-density sub-superficial graphitic microstructures can be created in diamond. Ion beam implantation is an effective tool for the structural modification of diamond: in particular ion-damaged diamond can be converted into graphite, therefore obtaining an electrically conductive phase embedded in an optically transparent and highly insulating matrix. The proposed fabrication process consists in the combination of Deep Ion Beam Lithography (DIBL) and Focused Ion Beam (FIB) milling. FIB micromachining is employed to define micro-apertures in the contact masks consisting of thin (<10 um) deposited metal layers through which ions are implanted in the sample. A prototypical single-cell biosensor was realized with the above described technique. The biosensor has 16 independent electrodes converging inside a circular area of 20 um diameter (typical neuroendocrine cells size) for the simultaneous recording of amperometric signals. △ Less

Submitted 6 December, 2014; originally announced December 2014.

Electrical stimulation of single-photon emission from nitrogen-vacancy centers in diamond with sub-superficial graphitic electrodes

Authors: J. Forneris, D. Gatto Monticone, P. Traina, V. Grilj, G. Brida, G. Amato, L. Boarino, E. Enrico, I. P. Degiovanni, E. Moreva, N. Skukan, M. Jakšić, M. Genovese, P. Olivero

Abstract: Focused MeV ion beams with micrometric resolution are suitable tools for the direct writing of conductive graphitic channels buried in an insulating diamond bulk. Their effectiveness has been shown for the fabrication of multi-electrode ionizing radiation detectors and cellular biosensors. In this work we investigate such fabrication method for the electrical excitation of color centers in diamond… ▽ More Focused MeV ion beams with micrometric resolution are suitable tools for the direct writing of conductive graphitic channels buried in an insulating diamond bulk. Their effectiveness has been shown for the fabrication of multi-electrode ionizing radiation detectors and cellular biosensors. In this work we investigate such fabrication method for the electrical excitation of color centers in diamond. Differently from optically-stimulated light emission from color centers in diamond, electroluminescence (EL) requires a high current flowing in the diamond subgap states between the electrodes. With this purpose, buried graphitic electrode pairs with a spacing of 10 $μ$m were fabricated in the bulk of a single-crystal diamond sample using a 6 MeV C microbeam. The electrical characterization of the structure showed a significant current above an effective voltage threshold of 150V, which was interpreted according to the theory of Space Charge Limited Current. The EL imaging allowed to identify the electroluminescent regions and the residual vacancy distribution associated with the fabrication technique. Measurements evidenced bright electroluminescent emission from native neutrally-charged nitrogen-vacancy centers ($NV^0$); the acquired spectra highlighted the absence of EL associated with radiation damage. △ Less

Submitted 12 September, 2014; v1 submitted 1 August, 2014; originally announced August 2014.

Comments: This article has been withdrawn due to the inclusion of additional upgrades and modifications, which significantly improve the paper. A new submission will be performed at a later stage

Electroluminescence from a diamond device with ion-beam-micromachined buried graphitic electrodes

Authors: J. Forneris, A. Battiato, D. Gatto Monticone, F. Picollo, G. Amato, L. Boarino, G. Brida, I. P. Degiovanni, E. Enrico, M. Genovese, E. Moreva, P. Traina, C. Verona, G. Verona-Rinati, P. Olivero

Abstract: Focused MeV ion microbeams are suitable tools for the direct writing of conductive graphitic channels buried in an insulating diamond bulk, as demonstrated in previous works with the fabrication of multi-electrode ionizing radiation detectors and cellular biosensors. In this work we investigate the suitability of the fabrication method for the electrical excitation of colour centres in diamond. Di… ▽ More Focused MeV ion microbeams are suitable tools for the direct writing of conductive graphitic channels buried in an insulating diamond bulk, as demonstrated in previous works with the fabrication of multi-electrode ionizing radiation detectors and cellular biosensors. In this work we investigate the suitability of the fabrication method for the electrical excitation of colour centres in diamond. Differently from photoluminescence, electroluminescence requires an electrical current flowing through the diamond sub-gap states for the excitation of the colour centres. With this purpose, buried graphitic electrodes with a spacing of 10 micrometers were fabricated in the bulk of a detector-grade CVD single-crystal diamond sample using a scanning 1.8 MeV He micro-beam. The current flowing in the gap region between the electrodes upon the application of a 250 V bias voltage was exploited as the excitation pump for the electroluminescence of different types of colour centres localized in the above-mentioned gap. The bright light emission was spatially mapped using a confocal optical microscopy setup. The spectral analysis of electroluminescence revealed the emission from neutrally-charged nitrogen-vacancy centres ($NV^0$, $λ_{ZPL}$ = 575 nm), as well as from cluster crystal dislocations (A-band, λ = 400-500 nm). Moreover, an electroluminescence signal with appealing spectral features (sharp emission at room temperature, low phonon sidebands) from He-related defects was detected ($λ_{ZPL}$ = 536.3 nm, $λ_{ZPL}$ = 560.5 nm); a low and broad peak around λ = 740 nm was also observed and tentatively ascribed to Si-V or GR1 centres. These results pose interesting future perspectives for the fabrication of electrically-stimulated single-photon emitters in diamond for applications in quantum optics and quantum cryptography. △ Less

Submitted 29 July, 2014; originally announced July 2014.

Journal ref: Nuclear Instruments and Methods in Physics Research B 348 (2015) 187

Native NIR-emitting single colour centres in CVD diamond

Authors: D. Gatto Monticone, P. Traina, E. Moreva, J. Forneris, P. Olivero, I. P. Degiovanni, F. Taccetti, L. Giuntini, G. Brida, G. Amato, M. Genovese

Abstract: Single-photon sources are a fundamental element for developing quantum technologies, and sources based on colour centres in diamonds are among the most promising candidates. The well-known NV centres are characterized by several limitations, thus few other defects have recently been considered. In the present work, we characterize in detail native efficient single colour centres emitting in the ne… ▽ More Single-photon sources are a fundamental element for developing quantum technologies, and sources based on colour centres in diamonds are among the most promising candidates. The well-known NV centres are characterized by several limitations, thus few other defects have recently been considered. In the present work, we characterize in detail native efficient single colour centres emitting in the near infra-red in both standard IIa single-crystal and electronic-grade polycrystalline commercial CVD diamond samples. In the former case, a high-temperature annealing process in vacuum is necessary to induce the formation/activation of luminescent centres with good emission properties, while in the latter case the annealing process has marginal beneficial effects on the number and performances of native centres in commercially available samples. Although displaying significant variability in several photo physical properties (emission wavelength, emission rate instabilities, saturation behaviours), these centres generally display appealing photophysical properties for applications as single photon sources: short lifetimes, high emission rates and strongly polarized light. The native centres are tentatively attributed to impurities incorporated in the diamond crystal during the CVD growth of high-quality type IIa samples, and offer promising perspectives in diamond-based photonics. △ Less

Submitted 18 March, 2014; originally announced March 2014.

Comments: 27 pages, 10 figures. Submitted to "New Journal of Phsyics", NJP-100003.R2

Journal ref: New Journal of Physics 16, 053005 (2014)

Measurement and modelling of anomalous polarity pulses in a multi-electrode diamond detector

Authors: J. Forneris, V. Grilj, M. Jaksic, P. Olivero, F. Picollo, N. Skukan, C. Verona, G. Verona-Rinati, E. Vittone

Abstract: In multi-electrode detectors, the motion of excess carriers generated by ionizing radiation induces charge pulses at the electrodes, whose intensities and polarities depend on the geometrical, electrostatic and carriers transport properties of the device. The resulting charge sharing effects may lead to bipolar currents, pulse height defects and anomalous polarity signals affecting the response of… ▽ More In multi-electrode detectors, the motion of excess carriers generated by ionizing radiation induces charge pulses at the electrodes, whose intensities and polarities depend on the geometrical, electrostatic and carriers transport properties of the device. The resulting charge sharing effects may lead to bipolar currents, pulse height defects and anomalous polarity signals affecting the response of the device to ionizing radiation. This latter effect has recently attracted attention in commonly used detector materials, but different interpretations have been suggested, depending on the material, the geometry of the device and the nature of the ionizing radiation. In this letter, we report on the investigation in the formation of anomalous polarity pulses in a multi-electrode diamond detector with buried graphitic electrodes. In particular, we propose a purely electrostatic model based on the Shockley-Ramo-Gunn theory, providing a satisfactory description of anomalous pulses observed in charge collection efficiency maps measured by means of Ion Beam Induced Charge (IBIC) microscopy, and suitable for a general application in multi-electrode devices and detectors. △ Less

Submitted 17 December, 2013; originally announced December 2013.

Comments: 8 pages, 4 figures

Systematic study of defect-related quenching of NV luminescence in diamond with time correlated single photon counting spectroscopy

Authors: D. Gatto Monticone, F. Quercioli, R. Mercatelli, S. Soria, S. Borini, T. Poli, M. Vannoni, E. Vittone, P. Olivero

Abstract: We report on the systematic characterization of photoluminescence (PL) lifetimes in NV- and NV0 centers in 2 MeV H+ implanted type Ib diamond samples by means of a time correlated single photon counting (TCSPC) microscopy technique. A dipole-dipole resonant energy transfer model was applied to interpret the experimental results, allowing a quantitative correlation of the concentration of both nati… ▽ More We report on the systematic characterization of photoluminescence (PL) lifetimes in NV- and NV0 centers in 2 MeV H+ implanted type Ib diamond samples by means of a time correlated single photon counting (TCSPC) microscopy technique. A dipole-dipole resonant energy transfer model was applied to interpret the experimental results, allowing a quantitative correlation of the concentration of both native (single substitutional nitrogen atoms) and ion-induced (isolated vacancies) PL-quenching defects with the measured PL lifetimes. The TCSPC measurements were carried out in both frontal (i.e. laser beam probing the main sample surface along the same normal direction of the previously implanted ions) and lateral (i.e. laser beam probing the lateral sample surface orthogonally with respect to the same ion implantation direction) geometries. In particular, the latter geometry allowed a direct probing of the centers lifetime along the strongly nonuniform damage profiles of MeV ions in the crystal. The extrapolation of empirical quasi-exponential decay parameters allowed the systematic estimation of the mean quantum efficiency of the centers as a function of intrinsic and ion-induced defect concentration, which is of direct relevance for the current studies on the use of diamond color centers for photonic applications. △ Less

Submitted 19 September, 2013; originally announced September 2013.

Comments: 39 pages, 12 figures

Journal ref: Physical Review B 88, 155201 (2013)

A new diamond biosensor with integrated graphitic microchannels for detecting quantal exocytic events from chromaffin cells

Authors: Federico Picollo, Sara Gosso, Ettore Vittone, Alberto Pasquarelli, Emilio Carbone, Paolo Olivero, Valentina Carabelli

Abstract: The quantal release of catecholamines from neuroendocrine cells is a key mechanism which has been investigated with a broad range of materials and devices, among which carbon-based materials such as carbon fibers, diamond-like carbon, carbon nanotubes and nanocrystalline diamond. In the present work we demonstrate that a MeV-ion-microbeam lithographic technique can be successfully employed for the… ▽ More The quantal release of catecholamines from neuroendocrine cells is a key mechanism which has been investigated with a broad range of materials and devices, among which carbon-based materials such as carbon fibers, diamond-like carbon, carbon nanotubes and nanocrystalline diamond. In the present work we demonstrate that a MeV-ion-microbeam lithographic technique can be successfully employed for the fabrication of an all-carbon miniaturized cellular bio-sensor based on graphitic micro-channels embedded in a single-crystal diamond matrix. The device was functionally characterized for the in vitro recording of quantal exocytic events from single chromaffin cells, with high sensitivity and signal-to-noise ratio, opening promising perspectives for the realization of monolithic all-carbon cellular biosensors. △ Less

Submitted 29 August, 2013; originally announced August 2013.

Direct measurement and modelling of internal strains in ion-implanted diamond

Authors: Federico Bosia, Nicola Argiolas, Marco Bazzan, Barbara A. Fairchild, Andrew D. Greentree, Desmond W. M. Lau, Paolo Olivero, Federico Picollo, Sergey Rubanov, Steven Prawer

Abstract: We present a phenomenological model and Finite Element simulations to describe the depth variation of mass density and strain of ion-implanted single-crystal diamond. Several experiments are employed to validate the approach: firstly, samples implanted with 180 keV B ions at relatively low fluences are characterized using high-resolution X-ray diffraction (HR-XRD); secondly, the mass density varia… ▽ More We present a phenomenological model and Finite Element simulations to describe the depth variation of mass density and strain of ion-implanted single-crystal diamond. Several experiments are employed to validate the approach: firstly, samples implanted with 180 keV B ions at relatively low fluences are characterized using high-resolution X-ray diffraction (HR-XRD); secondly, the mass density variation of a sample implanted with 500 keV He ions well above its amorphization threshold is characterized with Electron Energy Loss Spectroscopy (EELS). At high damage densities, the experimental depth profiles of strain and density display a saturation effect with increasing damage and a shift of the damage density peak towards greater depth values with respect to those predicted by TRIM simulations, which are well accounted for in the model presented here. The model is then further validated by comparing TEM-measured and simulated thickness values of a buried amorphous carbon layer formed at different depths by implantation of 500 keV He ions through a variable-thickness mask to simulate the simultaneous implantation of ions at different energies. △ Less

Submitted 1 March, 2013; originally announced March 2013.

Comments: 40 pages, 9 figures, submitted to Physical Review B

Splitting of photo-luminescent emission from nitrogen-vacancy centers in diamond induced by ion-damage-induced stress

Authors: P. Olivero, F. Bosia, B. A. Fairchild, B. C. Gibson, A. D. Greentree, P. Spizzirri, S. Prawer

Abstract: We report a systematic investigation on the spectral splitting of negatively charged, nitrogen-vacancy (NV-) photo-luminescent emission in single crystal diamond induced by strain engineering. The stress fields arise from MeV ion-induced conversion of diamond to amorphous and graphitic material in regions proximal to the centers of interest. In low-nitrogen sectors of a HPHT diamond, clearly disti… ▽ More We report a systematic investigation on the spectral splitting of negatively charged, nitrogen-vacancy (NV-) photo-luminescent emission in single crystal diamond induced by strain engineering. The stress fields arise from MeV ion-induced conversion of diamond to amorphous and graphitic material in regions proximal to the centers of interest. In low-nitrogen sectors of a HPHT diamond, clearly distinguishable spectral components in the NV- emission develop over a range of 4.8 THz corresponding to distinct alignment of sub-ensembles which were mapped with micron spatial resolution. This method provides opportunities for the creation and selection of aligned NV- centers for ensemble quantum information protocols. △ Less

Submitted 11 February, 2013; originally announced February 2013.

Comments: Submitted to "New Journal of Physics" (NJP/458519/PAP/133921): 30 pages, 12 figures, 2 tables, 61 references

Journal ref: New Journal of Physics 15, 043027 (2013)