Showing 1–31 of 31 results for author: Erbe, A

Geometry Dependence of Charge Transport in Nanoscopic Au@PANI Nanoparticle Assemblies

Authors: Gyusang Yi, Borja Rodriguez-Barea, Gabriele Carelli, Lukas Mielke, Andreas Fery, Artur Erbe, Hendrik Schlicke

Abstract: Hybrid nanostructures from metal nanoparticles equipped with conducting polymer shells are of great interest for use as functional materials in sensing and optoelectronics, as well as for ink-deposited conductors. Here, we investigate the charge transport mechanism of nanostructures composed of gold nanoparticles coated with a polyaniline shell (Au@PANI). In particular, we focus on how geometry in… ▽ More Hybrid nanostructures from metal nanoparticles equipped with conducting polymer shells are of great interest for use as functional materials in sensing and optoelectronics, as well as for ink-deposited conductors. Here, we investigate the charge transport mechanism of nanostructures composed of gold nanoparticles coated with a polyaniline shell (Au@PANI). In particular, we focus on how geometry influences the charge transport behavior. Highly ordered linear assemblies of Au@PANI nanoparticles were fabricated using template-assisted assembly, while bulk-like films were obtained via drop-casting. Temperature-dependent transport measurements were analyzed using established theoretical models. Linear assemblies exhibit more localized transport, characterized by variable-range hopping (VRH) and thermally assisted tunneling (TAT), whereas bulk-like films show more delocalized transport, dominated by Arrhenius-type and thermionic conduction. These findings highlight the critical role of geometry in determining charge transport mechanisms in nanoparticle-based hybrid systems. △ Less

Submitted 18 September, 2025; originally announced September 2025.

DNA mold-based fabrication of continuous silver nanostructures

Authors: Christoph Hadlich, Borja Rodriguez-Barea, Darius Pohl, Bernd Rellinghaus, Artur Erbe, Ralf Seidel

Abstract: Bottom-up fabrication of inorganic nanostructures is emerging as an alternative to classical top-down approaches, offering precise nanometer-scale control at relatively low cost and effort. In particular, DNA nanostructures provide versatile scaffolds for directly templating the growth of metal structures. Previously, a DNA mold-based method for metal nanostructure synthesis has been established t… ▽ More Bottom-up fabrication of inorganic nanostructures is emerging as an alternative to classical top-down approaches, offering precise nanometer-scale control at relatively low cost and effort. In particular, DNA nanostructures provide versatile scaffolds for directly templating the growth of metal structures. Previously, a DNA mold-based method for metal nanostructure synthesis has been established that supports a modular structure design and a high control over the structure formation. So far, this method was limited to the growth of gold and palladium nanostructures. Here, we report the successful adaptation of the DNA mold-based fabrication method to produce continuous silver nanowires. By optimizing reagent concentrations and applying gentle thermal annealing, we obtain continuous wire structures of several hundred nanometer length, overcoming limitations in anisotropic growth. Despite the strong interaction of silver ions with DNA, we can control the growth without increasing the complexity of our approach. Our structures are not oxidized yet they did not exhibit conductivity. This work demonstrates the versatility of DNA-templated metallization and opens new opportunities for constructing self-assembled hybrid nanostructures with controlled shape and composition. △ Less

Submitted 18 September, 2025; originally announced September 2025.

Intrinsic Resistive Switching in Microtubule-Templated Gold Nanowires for Reconfigurable Nanoelectronics

Authors: Borja Rodriguez-Barea, Brenda Palestina Romero, René Hübner, Stefan Diez, Artur Erbe

Abstract: The scaling limitations of conventional transistors demand alternative device concepts capable of dynamic reconfigurability at the atomic scale. Resistive switching (RS), a key mechanism for neuromorphic computing and non-volatile memory, has been widely demonstrated in oxides, semiconductors, and nanocomposites, but not in pure one-dimensional metallic systems. Here, we report the first electrica… ▽ More The scaling limitations of conventional transistors demand alternative device concepts capable of dynamic reconfigurability at the atomic scale. Resistive switching (RS), a key mechanism for neuromorphic computing and non-volatile memory, has been widely demonstrated in oxides, semiconductors, and nanocomposites, but not in pure one-dimensional metallic systems. Here, we report the first electrical characterization of gold nanowires (AuNWs) synthesized within the lumen of functionalized microtubules. Structural analyses confirm continuous metallic wires with local compositional inhomogeneities. Electrical measurements reveal three distinct conduction behaviours and abrupt, reversible resistance transitions under applied bias, consistent with defect-driven electromigration. Voltage pulsing enables active and reproducible modulation of resistance states without loss of metallic conduction, establishing a new RS mechanism intrinsic to pure metallic nanowires. Owing to their high aspect ratio, lateral geometry, and CMOS-compatible processing, microtubule-templated AuNWs provide a versatile platform for reconfigurable interconnects and neuromorphic device architectures. △ Less

Submitted 17 September, 2025; originally announced September 2025.

Comments: 23 pages, 15 figures, 1 table

Molecular Cross-linking of MXenes: Tunable Interfaces and Chemiresistive Sensing

Authors: Yudhajit Bhattacharjee, Lukas Mielke, Mahmoud Al-Hussein, Shivam Singh, Karen Schaefer, Borja Rodriguez-Barea, Qiong Li, Anik Kumar Ghosh, Artur Erbe, Carmen Herrmann, Yana Vaynzof, Andreas Fery, Hendrik Schlicke

Abstract: MXenes, a family of 2D transition metal compounds, have emerged as promising materials due to their unique electronic properties and tunable surface chemistry. However, the translation of these nanoscale properties into macroscopic devices is constrained by suitable cross-linking strategies that enable both processability and controlled inter-flake charge transport. Herein, we demonstrate the tuna… ▽ More MXenes, a family of 2D transition metal compounds, have emerged as promising materials due to their unique electronic properties and tunable surface chemistry. However, the translation of these nanoscale properties into macroscopic devices is constrained by suitable cross-linking strategies that enable both processability and controlled inter-flake charge transport. Herein, we demonstrate the tunability of interfaces and the inter-layer spacing between Ti$_3$C$_2$T$_x$ MXene flakes through molecular cross-linking with homologous diamines. Oleylamine was first used to stabilize MXenes in chloroform, followed by diamine-mediated cross-linking to tune precisely the interlayer spacing. Grazing incidence X-ray scattering (GIXRD/GIWAXS) confirmed the correlation between ligand chain length and inter-layer spacing, which was further supported by Density Functional Theory (DFT) calculations. Furthermore, we investigated the charge transport properties of thin films consisting of these diamine-crosslinked Ti$_3$C$_2$T$_x$ MXenes and observed a strong dependence of the conductivity on the interlayer spacing. The dominating charge transport mechanism is variable range hopping (VRH) in accordance with the structure analysis of the films. Finally, we probed chemiresistive vapor sensing in MXene composites, observing pronounced water sensitivity and selectivity, highlighting their potential for use in humidity sensors. Insights into molecular cross-linking and its impact on charge transport open avenues for next-generation MXene-based electronic devices. △ Less

Submitted 24 August, 2025; v1 submitted 15 April, 2025; originally announced April 2025.

Effect of Helium Ion Implantation on 3C-SiC Nanomechanical String Resonators

Authors: Philipp Bredol, Felix David, Nagesh S. Jagtap, Yannick S. Klaß, Georgy V. Astakhov, Artur Erbe, Eva M. Weig

Abstract: Hybrid quantum devices enable novel functionalities by combining the benefits of different subsystems. Particularly, point defects in nanomechanical resonators made of diamond or silicon carbide (SiC) have been proposed for precise magnetic field sensing and as versatile quantum transducers. However, the realization of a hybrid system may involve tradeoffs in the performance of the constituent sub… ▽ More Hybrid quantum devices enable novel functionalities by combining the benefits of different subsystems. Particularly, point defects in nanomechanical resonators made of diamond or silicon carbide (SiC) have been proposed for precise magnetic field sensing and as versatile quantum transducers. However, the realization of a hybrid system may involve tradeoffs in the performance of the constituent subsystems. In a spin-mechanical system, the mechanical properties of the resonator may suffer from the presence of engineered defects in the crystal lattice. This may severely restrict the performance of the resulting device and needs to be carefully explored. Here, we focus on the impact of defects on high Q nanomechanical string resonators made of pre-stressed 3C-SiC grown on Si(111). We use helium ion implantation to create point defects and study their accumulated effect on the mechanical performance. Using Euler-Bernoulli beam theory, we present a method to determine Young's modulus and the pre-stress of the strings. We find that Young's modulus is not modified by implantation. Under implantation doses relevant for single defect or defect ensemble generation, both tensile stress and damping rate also remain unaltered. For higher implantation dose, both exhibit a characteristic change. △ Less

Submitted 3 May, 2024; originally announced May 2024.

Probing the band splitting near the $Γ$ point in the van der Waals magnetic semiconductor CrSBr

Authors: Kaiman Lin, Yi Li, Mahdi Ghorbani-Asl, Zdenek Sofer, Stephan Winnerl, Artur Erbe, Arkady V. Krasheninnikov, Manfred Helm, Shengqiang Zhou, Yaping Dan, Slawomir Prucnal

Abstract: This study investigates the electronic band structure of Chromium Sulfur Bromide (CrSBr) through comprehensive photoluminescence (PL) characterization. We clearly identify low-temperature optical transitions between two closely adjacent conduction-band states and two different valence-band states. The analysis of the PL data robustly unveils energy splittings, bandgaps and excitonic transitions ac… ▽ More This study investigates the electronic band structure of Chromium Sulfur Bromide (CrSBr) through comprehensive photoluminescence (PL) characterization. We clearly identify low-temperature optical transitions between two closely adjacent conduction-band states and two different valence-band states. The analysis of the PL data robustly unveils energy splittings, bandgaps and excitonic transitions across different thicknesses of CrSBr, ranging from monolayer to bulk. Temperature-dependent PL measurements elucidate the stability of the band splitting below the Néel temperature, suggesting that magnons coupled with excitons are responsible for the symmetry breaking and brightening of the transitions from the secondary conduction band minimum (CBM2) to the global valence band maximum (VBM1). Collectively, these results not only reveal band splitting in both the conduction and valence bands, but also point to an intricate interplay between the optical, electronic and magnetic properties of antiferromagnetic two-dimensional van der Waals crystals. △ Less

Submitted 2 April, 2024; originally announced April 2024.

Lane formation in gravitationally driven colloid mixtures consisting of up to three different particle sizes

Authors: Kay Hofmann, Marc Isele, Artur Erbe, Paul Leiderer, Peter Nielaba

Abstract: Brownian dynamics simulations are utilized to study segregation phenomena far from thermodynamic equilibrium. In the present study, we expand upon the analysis of binary colloid mixtures and additionally introduce a third particle species to further our understanding of colloidal systems. Gravitationally driven, spherical colloids immersed in an implicit solvent are confined in two-dimensional lin… ▽ More Brownian dynamics simulations are utilized to study segregation phenomena far from thermodynamic equilibrium. In the present study, we expand upon the analysis of binary colloid mixtures and additionally introduce a third particle species to further our understanding of colloidal systems. Gravitationally driven, spherical colloids immersed in an implicit solvent are confined in two-dimensional linear microchannels. The interaction between the colloids is modeled by the Weeks-Chandler-Andersen potential, and the confinement of the colloids is realized by hard walls based on the solution of the Smoluchowski equation in half space. In binary and ternary colloidal systems, a difference in the driving force is achieved by differing colloid sizes, but fixed mass density. We observe for both the binary and ternary systems that a driving force difference induces a nonequilibrium phase transition to lanes. For ternary systems, we study the tendency of lane formation in dependence of the diameter of the medium-sized colloids. Here, we find a sweetspot for lane formation in ternary systems. Furthermore, we study the interaction of two differently sized colloids at the channel walls. Recently, we observed that driven large colloids push smaller colloids to the walls. This results in small particle lanes at the walls at early simulation times. In this work, we additionally find that thin lanes are unstable and dissolve over very long time frames. Furthermore, we observe a connection between lane formation and the nonuniform distribution of particles along the channel length. This nonuniform distribution occurs either alongside lane formation or in shared lanes (i.e. lanes consisting of two colloid types). △ Less

Submitted 10 January, 2024; originally announced January 2024.

Comments: Submitted to Physical Review E. 14 pages, 14 figures

Mid- and far-infrared localized surface plasmon resonances in chalcogen-hyperdoped silicon

Authors: Mao Wang, Ye Yu, Slawomir Prucnal, Yonder Berencén, Mohd Saif Shaikh, Lars Rebohle, Muhammad Bilal Khan, Vitaly Zviagin, René Hübner, Alexej Pashkin, Artur Erbe, Yordan M. Georgiev, Marius Grundmann, Manfred Helm, Robert Kirchner, Shengqiang Zhou

Abstract: Plasmonic sensing in the infrared region employs the direct interaction of the vibrational fingerprints of molecules with the plasmonic resonances, creating surface-enhanced sensing platforms that are superior than the traditional spectroscopy. However, the standard noble metals used for plasmonic resonances suffer from high radiative losses as well as fabrication challenges, such as tuning the sp… ▽ More Plasmonic sensing in the infrared region employs the direct interaction of the vibrational fingerprints of molecules with the plasmonic resonances, creating surface-enhanced sensing platforms that are superior than the traditional spectroscopy. However, the standard noble metals used for plasmonic resonances suffer from high radiative losses as well as fabrication challenges, such as tuning the spectral resonance positions into mid- to far-infrared regions, and the compatibility issue with the existing complementary metal-oxide-semiconductor (CMOS) manufacturing platform. Here, we demonstrate the occurrence of mid-infrared localized surface plasmon resonances (LSPR) in thin Si films hyperdoped with the known deep-level impurity tellurium. We show that the mid-infrared LSPR can be further enhanced and spectrally extended to the far-infrared range by fabricating two-dimensional arrays of micrometer-sized antennas in a Te-hyperdoped Si chip. Since Te-hyperdoped Si can also work as an infrared photodetector, we believe that our results will unlock the route toward the direct integration of plasmonic sensors with the one-chip CMOS platform, greatly advancing the possibility of mass manufacturing of high-performance plasmonic sensing systems. △ Less

Submitted 7 October, 2022; originally announced October 2022.

Comments: 20 pages, 5 figures

Journal ref: Nanoscale 14, 2826-2836 (2022)

Terahertz control of photoluminescence emission in few-layer InSe

Authors: Tommaso Venanzi, Malte Selig, Alexej Pashkin, Stephan Winnerl, Manuel Katzer, Himani Arora, Artur Erbe, Amalia Patanè, Zakhar R. Kudrynskyi, Zakhar D. Kovalyuk, Leonetta Baldassarre, Andreas Knorr, Manfred Helm, Harald Schneider

Abstract: A promising route for the development of opto-elelctronic technology is to use terahertz radiation to modulate the optical properties of semiconductors. Here we demonstrate the dynamical control of photoluminescence (PL) emission in few-layer InSe using picosecond terahertz pulses. We observe a strong PL quenching (up to 50%) after the arrival of the terahertz pulse followed by a reversible recove… ▽ More A promising route for the development of opto-elelctronic technology is to use terahertz radiation to modulate the optical properties of semiconductors. Here we demonstrate the dynamical control of photoluminescence (PL) emission in few-layer InSe using picosecond terahertz pulses. We observe a strong PL quenching (up to 50%) after the arrival of the terahertz pulse followed by a reversible recovery of the emission on the time scale of 50ps at T =10K. Microscopic calculations reveal that the origin of the photoluminescence quenching is the terahertz absorption by photo-excited carriers: this leads to a heating of the carriers and a broadening of their distribution, which reduces the probability of bimolecular electron-hole recombination and, therefore, the luminescence. By numerically evaluating the Boltzmann equation, we are able to clarify the individual roles of optical and acoustic phonons in the subsequent cooling process. The same PL quenchingmechanismis expected in other van derWaals semiconductors and the effectwill be particularly strong for materials with low carrier masses and long carrier relaxation time, which is the case for InSe. This work gives a solid background for the development of opto-electronic applications based on InSe, such as THz detectors and optical modulators. △ Less

Submitted 18 February, 2022; originally announced February 2022.

Comments: The following article has been accepted by Applied Physics Letters. After it is published, it will be found at https://publishing.aip.org/resources/librarians/products/journals/

A photonic platform hosting telecom photon emitters in silicon

Authors: Michael Hollenbach, Nagesh S. Jagtap, Ciarán Fowley, Juan Baratech, Verónica Guardia-Arce, Ulrich Kentsch, Anna Eichler-Volf, Nikolay V. Abrosimov, Artur Erbe, ChaeHo Shin, Hakseong Kim, Manfred Helm, Woo Lee, Georgy V. Astakhov, Yonder Berencén

Abstract: Silicon, a ubiquitous material in modern computing, is an emerging platform for realizing a source of indistinguishable single-photons on demand. The integration of recently discovered single-photon emitters in silicon into photonic structures, is advantageous to exploit their full potential for integrated photonic quantum technologies. Here, we show the integration of telecom photon emitters in a… ▽ More Silicon, a ubiquitous material in modern computing, is an emerging platform for realizing a source of indistinguishable single-photons on demand. The integration of recently discovered single-photon emitters in silicon into photonic structures, is advantageous to exploit their full potential for integrated photonic quantum technologies. Here, we show the integration of telecom photon emitters in a photonic platform consisting of silicon nanopillars. We developed a CMOS-compatible nanofabrication method, enabling the production of thousands of individual nanopillars per square millimeter with state-of-the-art photonic-circuit pitch, all the while being free of fabrication-related radiation damage defects. We found a waveguiding effect of the 1278 nm-G center emission along individual pillars accompanied by improved brightness, photoluminescence signal-to-noise ratio and photon extraction efficiency compared to that of bulk silicon. These results unlock clear pathways to monolithically integrating single-photon emitters into a photonic platform at a scale that matches the required pitch of quantum photonic circuits. △ Less

Submitted 5 December, 2021; originally announced December 2021.

Comments: 6 pages, 4 figures

Enhanced trion emission in monolayer MoSe2 by constructing a type-I van der Waals heterostructure

Authors: Juanmei Duan, Phanish Chava, Mahdi Ghorbani-Asl, Denise Erb, Liang Hu, Arkady V. Krasheninnikov, Harald Schneider, Lars Rebohle, Artur Erbe, Manfred Helm, Yu-Jia Zeng, Shengqiang Zhou, Slawomir Prucnal

Abstract: Trions, quasi-particles consisting of two electrons combined with one hole or of two holes with one electron, have recently been observed in transition metal dichalcogenides (TMDCs) and drawn increasing attention due to potential applications of these materials in light-emitting diodes, valleytronic devices as well as for being a testbed for understanding many-body phenomena. Therefore, it is impo… ▽ More Trions, quasi-particles consisting of two electrons combined with one hole or of two holes with one electron, have recently been observed in transition metal dichalcogenides (TMDCs) and drawn increasing attention due to potential applications of these materials in light-emitting diodes, valleytronic devices as well as for being a testbed for understanding many-body phenomena. Therefore, it is important to enhance the trion emission and its stability. In this study, we construct a MoSe2/FePS3 van der Waals heterostructure (vdWH) with type-I band alignment, which allows for carriers injection from FePS3 to MoSe2. At low temperatures, the neutral exciton (X0) emission in this vdWH is almost completely suppressed. The ITrion/Ix0 intensity ratio increases from 0.44 in a single MoSe2 monolayer to 20 in this heterostructure with the trion charging state changing from negative in the monolayer to positive in the heterostructure. The optical pumping with circularly polarized light shows a 14% polarization for the trion emission in MoSe2/FePS3. Moreover, forming such type-I vdWH also gives rise to a 20-fold enhancement of the room temperature photoluminescence from monolayer MoSe2. Our results demonstrate a novel approach to convert excitons to trions in monolayer 2D TMDCs via interlayer doping effect using type-I band alignment in vdWH. △ Less

Submitted 26 July, 2021; originally announced July 2021.

Comments: 21 pages, including the suppl. materials, accepted at Adv. Fun. Mater

Local and nonlocal spin Seebeck effect in lateral Pt-$\mathrm{Cr_2O_3}$-Pt devices at low temperatures

Authors: Prasanta Muduli, Richard Schlitz, Tobias Kosub, René Hübner, Artur Erbe, Denys Makarov, Sebastian T. B. Goennenwein

Abstract: We have studied thermally driven magnon spin transport (spin Seebeck effect, SSE) in heterostructures of antiferromagnetic $α$-$\mathrm{Cr_2O_3}$ and Pt at low temperatures. Monitoring the amplitude of the local and nonlocal SSE signals as a function of temperature, we found that both decrease with increasing temperature and disappear above 100 K and 20 K, respectively. Additionally, both SSE sign… ▽ More We have studied thermally driven magnon spin transport (spin Seebeck effect, SSE) in heterostructures of antiferromagnetic $α$-$\mathrm{Cr_2O_3}$ and Pt at low temperatures. Monitoring the amplitude of the local and nonlocal SSE signals as a function of temperature, we found that both decrease with increasing temperature and disappear above 100 K and 20 K, respectively. Additionally, both SSE signals show a tendency to saturate at low temperatures. The nonlocal SSE signal decays exponentially for intermediate injector-detector separation, consistent with magnon spin current transport in the relaxation regime. We estimate the magnon relaxation length of our $α$-$\mathrm{Cr_2O_3}$ films to be around 500 nm at 3 K. This short magnon relaxation length along with the strong temperature dependence of the SSE signal indicates that temperature-dependent inelastic magnon scattering processes play an important role in the intermediate range magnon transport. Our observation is relevant to low-dissipation antiferromagnetic magnon memory and logic devices involving thermal magnon generation and transport. △ Less

Submitted 11 February, 2021; v1 submitted 17 November, 2020; originally announced November 2020.

Comments: Accepted in APL Materials, For Supplementary Material see published version

Autocorrected Off-axis Holography of 2D Materials

Authors: Felix Kern, Martin Linck, Daniel Wolf, Nasim Alem, Himani Arora, Sibylle Gemming, Artur Erbe, Alex Zettl, Bernd Büchner, Axel Lubk

Abstract: The reduced dimensionality in two-dimensional materials leads a wealth of unusual properties, which are currently explored for both fundamental and applied sciences. In order to study the crystal structure, edge states, the formation of defects and grain boundaries, or the impact of adsorbates, high resolution microscopy techniques are indispensible. Here we report on the development of an electro… ▽ More The reduced dimensionality in two-dimensional materials leads a wealth of unusual properties, which are currently explored for both fundamental and applied sciences. In order to study the crystal structure, edge states, the formation of defects and grain boundaries, or the impact of adsorbates, high resolution microscopy techniques are indispensible. Here we report on the development of an electron holography (EH) transmission electron microscopy (TEM) technique, which facilitates high spatial resolution by an automatic correction of geometric aberrations. Distinguished features of EH beyond conventional TEM imaging are the gap-free spatial information signal transfer and higher dose efficiency for certain spatial frequency bands as well as direct access to the projected electrostatic potential of the 2D material. We demonstrate these features at the example of h-BN, at which we measure the electrostatic potential as a function of layer number down to the monolayer limit and obtain evidence for a systematic increase of the potential at the zig-zag edges. △ Less

Submitted 25 June, 2020; v1 submitted 24 June, 2020; originally announced June 2020.

Comments: 8 pages, 5 figures

Journal ref: Phys. Rev. Research 2, 043360 (2020)

Photoluminescence dynamics in few-layer InSe

Authors: Tommaso Venanzi, Himani Arora, Stephan Winnerl, Alexej Pashkin, Phanish Chava, Amalia Patanè, Zakhar D. Kovalyuk, Zalhar R. Kudrynskyi, Kenji Watanabe, Takashi Taniguchi, Artur Erbe, Manfred Helm, Harald Schneider

Abstract: We study the optical properties of thin flakes of InSe encapsulated in hBN. More specifically, we investigate the photoluminescence (PL) emission and its dependence on sample thickness and temperature. Through the analysis of the PL lineshape, we discuss the relative weights of the exciton and electron-hole contributions. Thereafter we investigate the PL dynamics. Two contributions are distinguish… ▽ More We study the optical properties of thin flakes of InSe encapsulated in hBN. More specifically, we investigate the photoluminescence (PL) emission and its dependence on sample thickness and temperature. Through the analysis of the PL lineshape, we discuss the relative weights of the exciton and electron-hole contributions. Thereafter we investigate the PL dynamics. Two contributions are distinguishable at low temperature: direct bandgap electron-hole and defect-assisted recombination. The two recombination processes have lifetime of $τ_1 \sim 8\;$ns and $τ_2 \sim 100\;$ns, respectively. The relative weights of the direct bandgap and defect-assisted contributions show a strong layer dependence due to the direct-to-indirect bandgap crossover. Electron-hole PL lifetime is limited by population transfer to lower-energy states and no dependence on the number of layers was observed. The lifetime of the defect-assisted recombination gets longer for thinner samples. Finally, we show that the PL lifetime decreases at high temperatures as a consequence of more efficient non-radiative recombinations. △ Less

Submitted 31 March, 2020; v1 submitted 27 March, 2020; originally announced March 2020.

Comments: The manuscript will be published in the journal Physical Review Materials. Copyright 2011 by American Physical Society (https://journals.aps.org/prmaterials/)

Focused ion beam modification of non-local magnon-based transport in yttrium iron garnet/platinum heterostructures

Authors: Richard Schlitz, Toni Helm, Michaela Lammel, Kornelius Nielsch, Artur Erbe, Sebastian T. B. Goennenwein

Abstract: We study the impact of Ga ion exposure on the local and non-local magnetotransport response in heterostructures of the ferrimagnetic insulator yttrium iron garnet and platinum. In particular, we cut the yttrium iron garnet layer in between two electrically separated wires of platinum using a Ga ion beam, and study the ensuing changes in the magnetoresistive response. We find that the non-local mag… ▽ More We study the impact of Ga ion exposure on the local and non-local magnetotransport response in heterostructures of the ferrimagnetic insulator yttrium iron garnet and platinum. In particular, we cut the yttrium iron garnet layer in between two electrically separated wires of platinum using a Ga ion beam, and study the ensuing changes in the magnetoresistive response. We find that the non-local magnetoresistance signal vanishes when the yttrium iron garnet film between the Pt wires is fully cut, although the local spin Hall magnetoresistance signal remains finite. This observation corroborates the notion that pure spin currents carried by magnons are crucial for the non-local magnetotransport effects observed in magnetic insulator/metal nanostructures. △ Less

Submitted 25 January, 2019; originally announced January 2019.

Comments: 5 pages, 3 figures

Emission and Propagation of Multi-Dimensional Spin Waves with nanoscale wavelengths in Anisotropic Spin Textures

Authors: V. Sluka, T. Schneider, R. A. Gallardo, A. Kakay, M. Weigand, T. Warnatz, R. Mattheis, A. Roldan-Molina, P. Landeros, V. Tiberkevich, A. Slavin, G. Schütz, A. Erbe, A. Deac, J. Lindner, J. Raabe, J. Fassbender, S. Wintz

Abstract: Spin waves offer intriguing novel perspectives for computing and signal processing, since their damping can be lower than the Ohmic losses in conventional CMOS circuits. For controlling the spatial extent and propagation of spin waves on the actual chip, magnetic domain walls show considerable potential as magnonic waveguides. However, low-loss guidance of spin waves with nanoscale wavelengths, in… ▽ More Spin waves offer intriguing novel perspectives for computing and signal processing, since their damping can be lower than the Ohmic losses in conventional CMOS circuits. For controlling the spatial extent and propagation of spin waves on the actual chip, magnetic domain walls show considerable potential as magnonic waveguides. However, low-loss guidance of spin waves with nanoscale wavelengths, in particular around angled tracks, remains to be shown. Here we experimentally demonstrate that such advanced control of propagating spin waves can be obtained using natural features of magnetic order in an interlayer exchange-coupled, anisotropic ferromagnetic bilayer. Using Scanning Transmission X-Ray Microscopy, we image generation of spin waves and their propagation across distances exceeding multiple times the wavelength, in extended planar geometries as well as along one-dimensional domain walls, which can be straight and curved. The observed range of wavelengths is between 1 μm and 150 nm, at corresponding excitation frequencies from 250 MHz to 3 GHz. Our results show routes towards practical implementation of magnonic waveguides employing domain walls in future spin wave logic and computational circuits. △ Less

Submitted 27 November, 2018; v1 submitted 2 July, 2018; originally announced July 2018.

CMOS-compatible controlled hyperdoping of silicon nanowires

Authors: Yonder Berencén, Slawomir Prucnal, Wolfhard Möller, René Hübner, Lars Rebohle, Roman Böttger, Markus Glaser, Tommy Schönherr, Ye Yuan, Mao Wang, Yordan M. Georgiev, Artur Erbe, Alois Lugstein, Manfred Helm, Shengqiang Zhou, Wolfgang Skorupa

Abstract: Hyperdoping consists of the intentional introduction of deep-level dopants into a semiconductor in excess of equilibrium concentrations. This causes a broadening of dopant energy levels into an intermediate band between the valence and conduction bands.[1,2] Recently, bulk Si hyperdoped with chalcogens or transition metals has been demonstrated to be an appropriate intermediate-band material for S… ▽ More Hyperdoping consists of the intentional introduction of deep-level dopants into a semiconductor in excess of equilibrium concentrations. This causes a broadening of dopant energy levels into an intermediate band between the valence and conduction bands.[1,2] Recently, bulk Si hyperdoped with chalcogens or transition metals has been demonstrated to be an appropriate intermediate-band material for Si-based short-wavelength infrared photodetectors.[3-5] Intermediate-band nanowires could potentially be used instead of bulk materials to overcome the Shockley-Queisser limit and to improve efficiency in solar cells,[6-9] but fundamental scientific questions in hyperdoping Si nanowires require experimental verification. The development of a method for obtaining controlled hyperdoping levels at the nanoscale concomitant with the electrical activation of dopants is, therefore, vital to understanding these issues. Here, we show a CMOS-compatible technique based on non-equilibrium processing for the controlled doping of Si at the nanoscale with dopant concentrations several orders of magnitude greater than the equilibrium solid solubility. Through the nanoscale spatially controlled implantation of dopants, and a bottom-up template-assisted solid phase recrystallization of the nanowires with the use of millisecond-flash lamp annealing, we form Se-hyperdoped Si/SiO2 core/shell nanowires that have a room-temperature sub-band gap optoelectronic photoresponse when configured as a photoconductor device. △ Less

Submitted 20 February, 2018; originally announced February 2018.

Comments: 21 pages, 4 figures (Main text)

Climbing two hills is faster than one: collective barrier-crossing by colloids driven through a microchannel

Authors: Urs Zimmermann, Hartmut Löwen, Christian Kreuter, Artur Erbe, Paul Leiderer, Frank Smallenburg

Abstract: Ohm's law is one of the most central transport rules stating that the total resistance of sequential single resistances is additive. While this rule is most commonly applied to electronic circuits, it also applies to other transport phenomena such as the flow of colloids or nanoparticles through channels containing multiple obstacles, as long as these obstacles are sufficiently far apart. Here we… ▽ More Ohm's law is one of the most central transport rules stating that the total resistance of sequential single resistances is additive. While this rule is most commonly applied to electronic circuits, it also applies to other transport phenomena such as the flow of colloids or nanoparticles through channels containing multiple obstacles, as long as these obstacles are sufficiently far apart. Here we explore the breakdown of Ohm's law for fluids of repulsive colloids driven over two energetic barriers in a microchannel, using real-space microscopy experiments, particle-resolved simulations, and dynamical density functional theory. If the barrier separation is comparable to the particle correlation length, the resistance is highly non-additive, such that the resistance added by the second barrier can be significantly higher or lower than that of the first. Surprisingly, in some cases the second barrier can even add a {\it negative} resistance, such that two identical barriers are easier to cross than a single one. We explain this counterintuitive observation in terms of the structuring of particles trapped between the barriers. △ Less

Submitted 10 September, 2020; v1 submitted 27 September, 2017; originally announced September 2017.

Stirrers and movers actuated by oscillating fields

Authors: Gabi Steinbach, Michael Schreiber, Dennis Nissen, Manfred Albrecht, Sibylle Gemming, Artur Erbe

Abstract: Locomotion via cyclic moves presents a challenge to mesoscopic objects in overdamped environments, where time reversibility may prevent directed motion. Most reported cyclic movers exploit anisotropic drag to push themselves forward. Under an oscillating drive, however, anisotropic drag enables locomotion only if the objects can change their shape. Here, we present a strategy that unexpectedly ena… ▽ More Locomotion via cyclic moves presents a challenge to mesoscopic objects in overdamped environments, where time reversibility may prevent directed motion. Most reported cyclic movers exploit anisotropic drag to push themselves forward. Under an oscillating drive, however, anisotropic drag enables locomotion only if the objects can change their shape. Here, we present a strategy that unexpectedly enables structurally invariant objects to move under oscillating fields. The objects are self-assembled clusters of magnetic particles that exhibit an off-centered dipole moment. By theoretical modeling and in experiments with magnetic Janus particles, we demonstrate that the interaction between such anisotropic particles in the cluster breaks time reversibility. Experimentally, we show that the magnetic configuration of a cluster determines its motion path. We realize stirrers and steerable movers with helical or directed path using the same particle system. The presented strategy based on internal interactions establishes a counterpart to locomotion via anisotropic drag. △ Less

Submitted 13 September, 2016; v1 submitted 16 July, 2016; originally announced July 2016.

Journal ref: Phys. Rev. Research 2, 023092 (2020)

Sub-harmonic resonant excitation of confined acoustic modes at GHz frequencies with a high-repetition-rate femtosecond laser

Authors: A. Bruchhausen, R. Gebs, F. Hudert, D. Issenmann, G. Klatt, A. Bartels, O. Schecker, R. Waitz, A. Erbe, E. Scheer, J. -R. Huntzinger, A. Mlayah, T. Dekorsy

Abstract: We propose sub-harmonic resonant optical excitation with femtosecond lasers as a new method for the characterization of phononic and nanomechanical systems in the gigahertz to terahertz frequency range. This method is applied for the investigation of confined acoustic modes in a free-standing semiconductor membrane. By tuning the repetition rate of a femtosecond laser through a sub-harmonic of a m… ▽ More We propose sub-harmonic resonant optical excitation with femtosecond lasers as a new method for the characterization of phononic and nanomechanical systems in the gigahertz to terahertz frequency range. This method is applied for the investigation of confined acoustic modes in a free-standing semiconductor membrane. By tuning the repetition rate of a femtosecond laser through a sub-harmonic of a mechanical resonance we amplify the mechanical amplitude, directly measure the linewidth with megahertz resolution, infer the lifetime of the coherently excited vibrational states, accurately determine the system's quality factor, and determine the amplitude of the mechanical motion with femtometer resolution. △ Less

Submitted 6 December, 2010; originally announced December 2010.

Density Reduction and Diffusion in Driven 2d-Colloidal Systems Through Microchannels

Authors: P. Henseler, A. Erbe, M. Köppl, P. Leiderer, P. Nielaba

Abstract: The behavior of particles driven through a narrow constriction is investigated in experiment and simulation. The system of particles adapts to the confining potentials and the interaction energies by a self-consistent arrangement of the particles. It results in the formation of layers throughout the channel and of a density gradient along the channel. The particles accommodate to the density gra… ▽ More The behavior of particles driven through a narrow constriction is investigated in experiment and simulation. The system of particles adapts to the confining potentials and the interaction energies by a self-consistent arrangement of the particles. It results in the formation of layers throughout the channel and of a density gradient along the channel. The particles accommodate to the density gradient by reducing the number of layers one by one when it is energetically favorable. The position of the layer reduction zone fluctuates with time while the particles continuously pass this zone. The flow behavior of the particles is studied in detail. The velocities of the particles and their diffusion behavior reflect the influence of the self-organized order of the system. △ Less

Submitted 13 October, 2008; originally announced October 2008.

Comments: 21 pages, 39 figures

Colloidal Micromotors: Controlled Directed Motion

Authors: Larysa Baraban, Christian Kreidler, Denys Makarov, Paul Leiderer, Artur Erbe

Abstract: Here we demonstrate a synthetic micro-engine, based on long-range controlled movement of colloidal particles, which is induced by a local catalytic reaction. The directed motion at long timescales was achieved by placing specially designed magnetic capped colloids in a hydrogen peroxide solution at weak magnetic fields. The control of the motion of the particles was provided by changes of the co… ▽ More Here we demonstrate a synthetic micro-engine, based on long-range controlled movement of colloidal particles, which is induced by a local catalytic reaction. The directed motion at long timescales was achieved by placing specially designed magnetic capped colloids in a hydrogen peroxide solution at weak magnetic fields. The control of the motion of the particles was provided by changes of the concentration of the solution and by varying the strength of the applied magnetic field. Such synthetic objects can then be used not only to understand the fundamental driving processes but also be employed as small motors in biological environments, for example, for the transportation of molecules in a controllable way. △ Less

Submitted 10 July, 2008; originally announced July 2008.

Comments: 14 pages, 3 figures

Influence of chopped laser light onto the electronic transport through atomic-sized contacts

Authors: D. C. Guhr, D. Rettinger, J. Boneberg, A. Erbe, P. Leiderer, E. Scheer

Abstract: This article reports on the influence of laser irradiation onto the electrical conductance of gold nanocontacts established with the mechanically controllable breakjunction technique (MCB). We concentrate here on the study of reversible conductance changes which can be as high as 200%. We investigate the dependence on the initial conductance of the contacts, the wavelength, the intensity and pos… ▽ More This article reports on the influence of laser irradiation onto the electrical conductance of gold nanocontacts established with the mechanically controllable breakjunction technique (MCB). We concentrate here on the study of reversible conductance changes which can be as high as 200%. We investigate the dependence on the initial conductance of the contacts, the wavelength, the intensity and position of the laser spot with respect to the sample. Under most conditions an enhancement of the conductance is observed. We discuss several physical mechanisms which might contribute to the observed effect including thermal expansion, rectification and photon-assisted transport. We conclude that thermal expansion is not the dominating one. △ Less

Submitted 26 September, 2007; v1 submitted 5 December, 2006; originally announced December 2006.

Comments: 20 pages with 7 figures; conference contribution on the 9th near field optics conference 2006 in Lausanne, Switzerland; accepted by the Journal of Microscopy

Lane reduction in driven 2d-colloidal systems through microchannels

Authors: M. Köppl, P. Henseler, A. Erbe, P. Nielaba, P. Leiderer

Abstract: The transport behavior of a system of gravitationally driven colloidal particles is investigated. The particle interactions are determined by the superparamagnetic behavior of the particles. They can thus be arranged in a crystalline order by application of an external magnetic field. Therefore the motion of the particles through a narrow channel occurs in well-defined lanes. The arrangement of… ▽ More The transport behavior of a system of gravitationally driven colloidal particles is investigated. The particle interactions are determined by the superparamagnetic behavior of the particles. They can thus be arranged in a crystalline order by application of an external magnetic field. Therefore the motion of the particles through a narrow channel occurs in well-defined lanes. The arrangement of the particles is perturbed by diffusion and the motion induced by gravity. Due to these combined influences a density gradient forms along the direction of motion of the particles. A reconfiguration of the crystal is observed leading to a reduction of the number of lanes. In the course of the lane reduction transition a local melting of the quasi-crystalline phase to a disordered phase and a subsequent crystallization along the motion of the particles is observed. This transition is characterized experimentally and using Brownian dynamics (BD) simulations. △ Less

Submitted 14 June, 2006; originally announced June 2006.

Comments: 4 pages, 4 figures

Capped colloids as light-mills in optical traps

Authors: F. S. Merkt, A. Erbe, P. Leiderer

Abstract: Custom-designed colloidal particles in an optical tweezers act as light-mills in a fluid. In particular, aqueous suspensions of capped colloids, in which half of the surface is covered with metal layers, are investigated. Due to their asymmetry, the capped colloids can act as rotators when exposed to intense laser fields. Particles of 4.7 micrometer in diameter are observed rotating around the f… ▽ More Custom-designed colloidal particles in an optical tweezers act as light-mills in a fluid. In particular, aqueous suspensions of capped colloids, in which half of the surface is covered with metal layers, are investigated. Due to their asymmetry, the capped colloids can act as rotators when exposed to intense laser fields. Particles of 4.7 micrometer in diameter are observed rotating around the focus of a laser beam. For low intensities, particles become trapped close to the spot of highest laser intensity. Above a threshold value of about 4 mW in total beam intensity, the particles move away from the center of the focus and start to rotate at frequencies of about 1 Hz. The balance of forces due to light pressure and hydrodynamic forces gives a constant rotation rate. The speed of the spinning particle increases linearly with laser power to above 2 Hz until the particles are ejected from the focus for intensities higher than 7 mW. Magnetic caps introduce further possibilities to tune the rotation rates. △ Less

Submitted 18 May, 2006; originally announced May 2006.

Comments: 8 pages, 4 figures, video unavailable

Control of topography, stress and diffusion at molecule-metal interface

Authors: Nikolai B. Zhitenev, Weirong Jiang, Artur Erbe, Zhenan Bao, Eric Garfunkel, Donald M. Tennant, Raymond A. Cirelli

Abstract: Transport properties of metal-molecule-metal junctions containing monolayer of conjugated and saturated molecules with characteristic dimensions in the range of 30-300 nm are correlated with microscopic topography, stress and chemical bonding at metal-molecule interfaces. Our statistically significant dataset allows us to conclude that the conductivity of organic molecules ~1.5 nm long is at lea… ▽ More Transport properties of metal-molecule-metal junctions containing monolayer of conjugated and saturated molecules with characteristic dimensions in the range of 30-300 nm are correlated with microscopic topography, stress and chemical bonding at metal-molecule interfaces. Our statistically significant dataset allows us to conclude that the conductivity of organic molecules ~1.5 nm long is at least 4 orders of magnitude lower than is commonly believed. △ Less

Submitted 13 October, 2005; originally announced October 2005.

Comments: 12 pages, 4 figures

A nanomechanical resonator shuttling single electrons at radio frequencies

Authors: A. Erbe, C. Weiss, W. Zwerger, R. H. Blick

Abstract: We observe transport of electrons through a metallic island on the tip of a nanomechanical pendulum. The resulting tunneling current shows distinct features corresponding to the discrete mechanical eigenfrequencies of the pendulum. We report on measurements covering the temperature range from 300 K down to 4.2 K. We explain the I-V curve, which differs from previous theoretical predictions, with… ▽ More We observe transport of electrons through a metallic island on the tip of a nanomechanical pendulum. The resulting tunneling current shows distinct features corresponding to the discrete mechanical eigenfrequencies of the pendulum. We report on measurements covering the temperature range from 300 K down to 4.2 K. We explain the I-V curve, which differs from previous theoretical predictions, with model calculations based on a Master equation approach. △ Less

Submitted 24 November, 2000; originally announced November 2000.

Comments: 5 pages, 4 jpeg-figures

Journal ref: Phys. Rev. Lett. 87, 096106 (2001)

Comparing schemes of displacement detection and subharmonic generation in nanomachined mechanical resonators

Authors: Florian W. Beil, Laura Pescini, Eva Höhberger, Andreas Kraus, Artur Erbe, Robert H. Blick

Abstract: We present measurements on nanomechanical resonators operating in the radio frequency range. We apply a setup which allows the comparison of two schemes of displacement detection for mechanical resonators, namely conventional power reflection measurements of a probing signal and direct detection by capacitive coupling via a gate electrode. For capacitive detection, we employ an on-chip preamplif… ▽ More We present measurements on nanomechanical resonators operating in the radio frequency range. We apply a setup which allows the comparison of two schemes of displacement detection for mechanical resonators, namely conventional power reflection measurements of a probing signal and direct detection by capacitive coupling via a gate electrode. For capacitive detection, we employ an on-chip preamplifier, which enables direct measurements of the resonator's displacement. We observe that the response of the mechanical resonator depends on the detection technique applied, which is verified in model calculations. We show results on the detection of subharmonics.-Paper withdrawn △ Less

Submitted 15 May, 2002; v1 submitted 17 November, 2000; originally announced November 2000.

Comments: 8 pages, 3 figures

Mechanical Mixing in Nonlinear Nanomechanical Resonators

Authors: A. Erbe, G. Corso, H. Krommer, A. Kraus, K. Richter, R. H. Blick

Abstract: Nanomechanical resonators, machined out of Silicon-on-Insulator wafers, are operated in the nonlinear regime to investigate higher-order mechanical mixing at radio frequencies, relevant to signal processing and nonlinear dynamics on nanometer scales. Driven by two neighboring frequencies the resonators generate rich power spectra exhibiting a multitude of satellite peaks. This nonlinear response… ▽ More Nanomechanical resonators, machined out of Silicon-on-Insulator wafers, are operated in the nonlinear regime to investigate higher-order mechanical mixing at radio frequencies, relevant to signal processing and nonlinear dynamics on nanometer scales. Driven by two neighboring frequencies the resonators generate rich power spectra exhibiting a multitude of satellite peaks. This nonlinear response is studied and compared to $n^{th}$-order perturbation theory and nonperturbative numerical calculations. △ Less

Submitted 15 December, 1999; originally announced December 1999.

Comments: 5 pages, 7 figures

Report number: mpi-pks/9912003

Nanomechanical vibrating wire resonator for phonon spectroscopy in Helium

Authors: Andreas Kraus, Artur Erbe, Robert H. Blick

Abstract: We demonstrate how to build a vibrating wire resonator for phonon excitation in liquid helium. The resonator is designed as a nanoscopic mechanically flexible beam machined out of a semiconductor/metal-hybrid. Quenching of the mechanical resonance around 100 MHz by phonon excitation in liquid ^4He at 4.2 K is shown. First measurements operating the nano-resonator in a dilution of ^3He/^4He at 30… ▽ More We demonstrate how to build a vibrating wire resonator for phonon excitation in liquid helium. The resonator is designed as a nanoscopic mechanically flexible beam machined out of a semiconductor/metal-hybrid. Quenching of the mechanical resonance around 100 MHz by phonon excitation in liquid ^4He at 4.2 K is shown. First measurements operating the nano-resonator in a dilution of ^3He/^4He at 30 mK are presented. △ Less

Submitted 2 December, 1999; originally announced December 1999.

Comments: 4pages, 4 figures

Nanomechanical resonators operating as charge detectors in the nonlinear regime

Authors: H. Kroemmer, A. Erbe, A. Tilke, S. Manus, R. H. Blick

Abstract: We present measurements on nanomechanical resonators machined from Silicon-on-Insulator substrates. The resonators are designed as freely suspended Au/Si beams of lengths on the order of 1 - 4 um and a thickness of 200 nm. The beams are driven into nonlinear response by an applied modulation at radio frequencies and a magnetic field in plane. The strong hysteresis of the magnetomotive response a… ▽ More We present measurements on nanomechanical resonators machined from Silicon-on-Insulator substrates. The resonators are designed as freely suspended Au/Si beams of lengths on the order of 1 - 4 um and a thickness of 200 nm. The beams are driven into nonlinear response by an applied modulation at radio frequencies and a magnetic field in plane. The strong hysteresis of the magnetomotive response allows sensitive charge detection by varying the electrostatic potential of a gate electrode. △ Less

Submitted 21 October, 1999; originally announced October 1999.

Comments: 8 pages, 6 figures