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Atomically Thin Amorphous Carbon with an Ultralow Dielectric Constant
Authors:
Chee-Tat Toh,
Artem K. Grebenko,
Ugur Karadeniz,
Usha Bhat,
Ya He,
Hongji Zhang,
Denis V. Vyalikh,
Anna Makarova,
Alexander Fedorov,
Alena A. Alekseeva,
Kostya Iakoubovskii,
Lu Shi,
Andrei Starkov,
Chuan Chu Tee,
Lucas M. Sassi,
Michel Bosman,
Naoto Kamiuchi,
Yuta Sato,
Kazutomo Suenaga,
Barbaros Oezyilmaz
Abstract:
Two-dimensional (2D) materials exhibit excellent properties at monolayer thickness and are viable replacements for various microelectronic components as scaling gradually approaches the atomic limit. Despite significant advancements in the ongoing 2D revolution of integrated circuits, one crucial building block, namely a 2D ultralow-k (ULK) dielectric, remains unreported. The challenge lies in ach…
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Two-dimensional (2D) materials exhibit excellent properties at monolayer thickness and are viable replacements for various microelectronic components as scaling gradually approaches the atomic limit. Despite significant advancements in the ongoing 2D revolution of integrated circuits, one crucial building block, namely a 2D ultralow-k (ULK) dielectric, remains unreported. The challenge lies in achieving a dielectric constant less than 3, as traditional low-k dielectrics are inherently unstable at the 2D limit due to their amorphous or porous nature. The realisation of ultrathin dielectrics with low-k is also needed to address current bottlenecks in integrated circuits scaling. Specifically, low-k materials are necessary to minimise parasitic capacitances as the distance between conductive elements shrinks below 10 nm. Moreover, advanced architectures like gate-all-around field effect transistors (GAA FET) require even lower dielectric constants (k<2) at sub-3nm thickness. Here, we show that layer-by-layer grown multilayer amorphous carbon (ML-AC), as thin as 0.8 nm, is a mechanically robust 2D ULK dielectric with k of 1.35 and dielectric strength of 28-31 MV cm-1. The lack of any long-range order, its intrinsic 2D nature, sp2 carbon character and low density are all essential for minimising dielectric permittivity. Moreover, ML-AC overcomes the vulnerability of existing dielectrics to ion diffusion degradation with a record metal ion diffusion time to failure (TTF) of 10^10 s for even a single layer. Therefore, otherwise necessary additional layers occupying up to 3 nm can be eliminated, which is especially significant as metal line widths approach 10 nm. Combined with its low-temperature, direct and conformal growth even on a dielectric, these critical features enable substantial improvements in silicon-based semiconductor electronics and ensure compatibility with future 2D electronics.
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Submitted 28 June, 2026;
originally announced June 2026.
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Particle-In-Cell Simulations of Quantum Plasmas
Authors:
Gregory K. Ngirmang,
Hue T. B. Do,
Guangxin Liu,
Michel Bosman,
Lin Wu
Abstract:
Room-temperature metals and semi-metals which consist of a gas of bound electrons in a near-continuum band structure can be classified as cold quantum plasmas. This insight suggests that Particle-in-Cell (PIC) simulations, traditionally used for modeling classical plasmas, may be adapted for the next generation of nanoscopic simulations in photonics, plasmonics, and beyond. This article introduces…
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Room-temperature metals and semi-metals which consist of a gas of bound electrons in a near-continuum band structure can be classified as cold quantum plasmas. This insight suggests that Particle-in-Cell (PIC) simulations, traditionally used for modeling classical plasmas, may be adapted for the next generation of nanoscopic simulations in photonics, plasmonics, and beyond. This article introduces four key physics modules implemented in two open-source PIC codes that can be applied to condensed matter calculations. These modules include (I) the incorporation of Fermi-Dirac (FD) electrons, (II) material structure boundary conditions, (III) a bound particle model for linear dispersive materials, and (IV) the inclusion of massless Dirac carriers for simulating graphene-like materials. By integrating these modules into existing PIC frameworks, we provide a versatile and self-consistent approach for simulating condensed matter systems, opening new avenues for modeling dynamic phenomena in photonics and plasmonics.
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Submitted 13 January, 2025;
originally announced January 2025.
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Nonlinear Terahertz Resonances from Ballistic Electron Funnelling
Authors:
Hue T. B. Do,
Gregory K. Ngirmang,
Wu Lin,
Michel Bosman
Abstract:
We introduce a new mechanism for second-harmonic generation through geometrically rectifying-funneling-ballistic electrons in THz optical resonators. Our resonant rectifiers inherently act as second-order harmonic generators, rectifying currents without the presence of a potential barrier. Particle-in-cell simulations reveal that femtosecond electron-surface scattering plays a critical role in thi…
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We introduce a new mechanism for second-harmonic generation through geometrically rectifying-funneling-ballistic electrons in THz optical resonators. Our resonant rectifiers inherently act as second-order harmonic generators, rectifying currents without the presence of a potential barrier. Particle-in-cell simulations reveal that femtosecond electron-surface scattering plays a critical role in this process. We differentiate electron funneling from nonlocal plasmonic drag and bulk Dirac anharmonicity, showing that funneling can reduce the required field intensity for second-harmonic generation by 3-4 orders of magnitude. We provide design guidelines for generating funneling-induced second-harmonic generation, including resonance mode matching and materials selection. This approach offers a practical pathway for low-field, geometrically tunable THz upconversion and rectification, operating from sub-10 THz to multiple tens of THz in graphene.
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Submitted 30 April, 2025; v1 submitted 14 November, 2024;
originally announced November 2024.
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Liquid Metal Oxide-assisted Integration of High-k Dielectrics and Metal Contacts for Two-Dimensional Electronics
Authors:
Dasari Venkatakrishnarao,
Abhishek Mishra,
Yaoju Tarn,
Michel Bosman,
Rainer Lee,
Sarthak Das,
Subhrajit Mukherjee,
Teymour Talha-Dean,
Yiyu Zhang,
Siew Lang Teo,
Jian Wei Chai,
Fabio Bussolotti,
Kuan Eng Johnson Goh,
Chit Siong Lau
Abstract:
Two-dimensional van der Waals semiconductors are promising for future nanoelectronics. However, integrating high-k gate dielectrics for device applications is challenging as the inert van der Waals material surfaces hinder uniform dielectric growth. Here, we report a liquid metal oxide-assisted approach to integrate ultrathin, high-k HfO2 dielectric on 2D semiconductors with atomically smooth inte…
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Two-dimensional van der Waals semiconductors are promising for future nanoelectronics. However, integrating high-k gate dielectrics for device applications is challenging as the inert van der Waals material surfaces hinder uniform dielectric growth. Here, we report a liquid metal oxide-assisted approach to integrate ultrathin, high-k HfO2 dielectric on 2D semiconductors with atomically smooth interfaces. Using this approach, we fabricated 2D WS2 top-gated transistors with subthreshold swings down to 74.5 mV/dec, gate leakage current density below 10-6 A/cm2, and negligible hysteresis. We further demonstrate a one-step van der Waals integration of contacts and dielectrics on graphene. This can offer a scalable approach toward integrating entire prefabricated device stack arrays with 2D materials. Our work provides a scalable solution to address the crucial dielectric engineering challenge for 2D semiconductors, paving the way for high-performance 2D electronics.
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Submitted 19 September, 2024;
originally announced September 2024.
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Robust Ptychographic Reconstruction with an Out-of-Focus Electron Probe
Authors:
Shoucong Ning,
Wenhui Xu,
Pengju Sheng,
Leyi Loh,
Stephen Pennycook,
Fucai Zhang,
Michel Bosman,
Qian He
Abstract:
As a burgeoning technique, out-of-focus electron ptychography offers the potential for rapidly imaging atomic-scale large fields of view (FoV) using a single diffraction dataset. However, achieving robust out-of-focus ptychographic reconstruction poses a significant challenge due to the inherent scan instabilities of electron microscopes, compounded by the presence of unknown aberrations in the pr…
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As a burgeoning technique, out-of-focus electron ptychography offers the potential for rapidly imaging atomic-scale large fields of view (FoV) using a single diffraction dataset. However, achieving robust out-of-focus ptychographic reconstruction poses a significant challenge due to the inherent scan instabilities of electron microscopes, compounded by the presence of unknown aberrations in the probe-forming lens. In this study, we substantially enhance the robustness of out-of-focus ptychographic reconstruction by extending our previous calibration method (the Fourier method), which was originally developed for the in-focus scenario. This extended Fourier method surpasses existing calibration techniques by providing more reliable and accurate initialization of scan positions and electron probes. Additionally, we comprehensively explore and recommend optimized experimental parameters for robust out-of-focus ptychography, includingaperture size and defocus, through extensive simulations. Lastly, we conduct a comprehensive comparison between ptychographic reconstructions obtained with focused and defocused electron probes, particularly in the context of low-dose and precise phase imaging, utilizing our calibration method as the basis for evaluation.
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Submitted 22 June, 2024;
originally announced June 2024.
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Liquid Metal Printed Ultrathin Oxides for Monolayer WS2 Top-Gate Transistors
Authors:
Yiyu Zhang,
Dasari Venkatakrishnarao,
Michel Bosman,
Wei Fu,
Sarthak Das,
Fabio Bussolotti,
Rainer Lee,
Siew Lang Teo,
Ding Huang,
Ivan Verzhbitskiy,
Zhuojun Jiang,
Zhuoling Jiang,
Jian Wei Chai,
Shi Wun Tong,
Zi-En Ooi,
Calvin Pei Yu Wong,
Yee Sin Ang,
Kuan Eng Johnson Goh,
Chit Siong Lau
Abstract:
Two-dimensional (2D) semiconductors are promising channel materials for continued downscaling of complementary metal-oxide-semiconductor (CMOS) logic circuits. However, their full potential continues to be limited by a lack of scalable high-k dielectrics that can achieve atomically smooth interfaces, small equivalent oxide thicknesses (EOT), excellent gate control, and low leakage currents. Here,…
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Two-dimensional (2D) semiconductors are promising channel materials for continued downscaling of complementary metal-oxide-semiconductor (CMOS) logic circuits. However, their full potential continues to be limited by a lack of scalable high-k dielectrics that can achieve atomically smooth interfaces, small equivalent oxide thicknesses (EOT), excellent gate control, and low leakage currents. Here, we report liquid metal printed ultrathin and scalable Ga2O3 dielectric for 2D electronics and electro-optical devices. We directly visualize the atomically smooth Ga2O3/WS2 interfaces enabled by the conformal nature of liquid metal printing. We demonstrate atomic layer deposition compatibility with high-k Ga2O3/HfO2 top-gate dielectric stacks on chemical vapour deposition grown monolayer WS2, achieving EOTs of ~1 nm and subthreshold swings down to 84.9 mV/dec. Gate leakage currents are well within requirements for ultra-scaled low-power logic circuits. Our results show that liquid metal printed oxides can bridge a crucial gap in scalable dielectric integration of 2D materials for next-generation nano-electronics.
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Submitted 25 October, 2022;
originally announced October 2022.
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Single-shot, coherent, pop-out 3D metrology
Authors:
Deepan Balakrishnan,
See Wee Chee,
Zhaslan Baraissov,
Michel Bosman,
Utkur Mirsaidov,
N. Duane Loh
Abstract:
Three-dimensional (3D) imaging of thin, extended specimens at nanometer resolution is critical for applications in biology, materials science, advanced synthesis, and manufacturing. One route to 3D imaging is tomography, which requires a tilt series of a local region. Here we describe a coherent imaging alternative that recovers the 3D volume of a thin, homogeneously amorphous specimen with only a…
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Three-dimensional (3D) imaging of thin, extended specimens at nanometer resolution is critical for applications in biology, materials science, advanced synthesis, and manufacturing. One route to 3D imaging is tomography, which requires a tilt series of a local region. Here we describe a coherent imaging alternative that recovers the 3D volume of a thin, homogeneously amorphous specimen with only a single, energy-filtered, bright-field image. We demonstrated this technique with a transmission electron microscope to fill a glaring gap for rapid, accessible, non-destructive 3D nanometrology. This technique is applicable, in general, to any coherent bright field imaging with electrons, photons, or any other wavelike particles.
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Submitted 20 October, 2023; v1 submitted 7 September, 2022;
originally announced September 2022.
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Low energy switching of phase change materials using a 2D thermal boundary layer
Authors:
Jing Ning,
Yunzheng Wang,
Ting Yu Teo,
Chung-Che Huang,
Ioannis Zeimpekis,
Katrina Morgan,
Siew Lang Teo,
Daniel W. Hewak,
Michel Bosman,
Robert E. Simpson
Abstract:
The switchable optical and electrical properties of phase change materials (PCMs) are finding new applications beyond data storage in reconfigurable photonic devices. However, high power heat pulses are needed to melt-quench the material from crystalline to amorphous. This is especially true in silicon photonics, where the high thermal conductivity of the waveguide material makes heating the PCM e…
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The switchable optical and electrical properties of phase change materials (PCMs) are finding new applications beyond data storage in reconfigurable photonic devices. However, high power heat pulses are needed to melt-quench the material from crystalline to amorphous. This is especially true in silicon photonics, where the high thermal conductivity of the waveguide material makes heating the PCM energy inefficient. Here, we improve the energy efficiency of the laser-induced phase transitions by inserting a layer of two-dimensional (2D) material, either MoS2 or WS2, between the silica or silicon and the PCM. The 2D material reduces the required laser power by at least 40% during the amorphization (RESET) process, depending on the substrate. Thermal simulations confirm that both MoS2 and WS2 2D layers act as a thermal barrier, which efficiently confines energy within the PCM layer. Remarkably, the thermal insulation effect of the 2D layer is equivalent to a ~100 nm layer of SiO2. The high thermal boundary resistance induced by the van der Waals (vdW)-bonded layers limits the thermal diffusion through the layer interfaces. Hence, 2D materials with stable vdW interfaces can be used to improve the thermal efficiency of PCM-tuned Si photonic devices. Furthermore, our waveguide simulations show that the 2D layer does not affect the propagating mode in the Si waveguide, thus this simple additional thin film produces a substantial energy efficiency improvement without degrading the optical performance of the waveguide. Our findings pave the way for energy-efficient laser-induced structural phase transitions in PCM-based reconfigurable photonic devices.
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Submitted 9 February, 2022;
originally announced February 2022.
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A scheme for simulating multi-level phase change photonics materials
Authors:
Yunzheng Wang,
Jing Ning,
Li Lu,
Michel Bosman,
Robert E. Simpson
Abstract:
Chalcogenide phase change materials (PCMs) have been extensively applied in data storage, and they are now being proposed for high resolution displays, holographic displays, reprogrammable photonics, and all-optical neural networks. These wide-ranging applications all exploit the radical property contrast between the PCMs different structural phases, extremely fast switching speed, long-term stabi…
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Chalcogenide phase change materials (PCMs) have been extensively applied in data storage, and they are now being proposed for high resolution displays, holographic displays, reprogrammable photonics, and all-optical neural networks. These wide-ranging applications all exploit the radical property contrast between the PCMs different structural phases, extremely fast switching speed, long-term stability, and low energy consumption. Designing PCM photonic devices requires an accurate model to predict the response of the device during phase transitions. Here, we describe an approach that accurately predicts the microstructure and optical response of phase change materials during laser induced heating. The framework couples the Gillespie Cellular Automata approach for modelling phase transitions with effective medium theory and Fresnel equations. The accuracy of the approach is verified by comparing the PCM optical response and microstructure evolution with the results of nanosecond laser switching experiments. We anticipate that this approach to simulating the switching response of PCMs will become an important component for designing and simulating programmable photonics devices. The method is particularly important for predicting the multi-level optical response of PCMs, which is important for all-optical neural networks and PCM-programmable perceptrons.
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Submitted 5 July, 2021;
originally announced July 2021.
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Photonic Bound-States-in-the-Continuum Observed with an Electron Nanoprobe
Authors:
Zhaogang Dong,
Zackaria Mahfoud,
Ramón Paniagua-Domínguez,
Hongtao Wang,
Antonio I. Fernández-Domínguez,
Sergey Gorelik,
Son Tung Ha,
Febiana Tjiptoharsono,
Arseniy I. Kuznetsov,
Michel Bosman,
Joel K. W. Yang
Abstract:
Bound-states-in-the-continuum (BIC)is a wave-mechanical concept that generates resonances with vanishing spectral linewidths. It has many practical applications in Optics, such as narrow-band filters, mirror-less lasing, and nonlinear harmonic generation. As true BIC optical modes non-radiative and confined to the near field of nanostructures, they cannot be excited using propagating light. As a r…
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Bound-states-in-the-continuum (BIC)is a wave-mechanical concept that generates resonances with vanishing spectral linewidths. It has many practical applications in Optics, such as narrow-band filters, mirror-less lasing, and nonlinear harmonic generation. As true BIC optical modes non-radiative and confined to the near field of nanostructures, they cannot be excited using propagating light. As a result, their direct experimental observation has been elusive. Rather than using light, we demonstrate probing BIC modes on arrays of silicon nanoantennas using a focused beam of electrons in a tranmission electron microscope. By combining cathodoluminescence (CL) and monochromated electron energy-loss spectroscopy (EELS) with controlled nanofabrication, we provide direct experimental evidence of "true" BIC modes, and demonstrate a BIC mode in the visible spectrum at 720 nm. The ability to observe and quantify these guided resonances with a spatial precision more than two orders of magnitude higher than previous far-field measurements allows the probing of individual elements in the nano-antenna arrays. The high-resolution experimental results are supported by numerical simulations as well as multipolar decomposition analysis, allowing us to demonstrate that the coherent interaction length of the quasi-BIC resonance requires at least 6 neighboring antenna elements, achieving over 60 times higher emissivity than for unpatterned silicon.
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Submitted 10 May, 2021;
originally announced May 2021.
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The Cesium Source Calibration and Monitoring System of the ATLAS Tile Calorimeter: Design, Construction and Results
Authors:
G. Blanchot,
M. Bosman,
J. Budagov,
M. Cavalli-Sforza,
I. Efthymiopoulos,
A. Isaev,
Y. Ivanyushenkov,
A. Karyukhin,
S. Kopikov,
M. Nessi,
V. Senko,
N. Shalanda,
M. Soldatov,
A. Solodkov,
O. Solovyanov,
E. Starchenko,
V. Tsoupko-Sitnikov,
I. Vichou,
A. Zaitsev
Abstract:
This article describes the design, construction and use of a calibration and monitoring system, based on movable 137Cs gamma-ray sources, for the ATLAS Tile Calorimeter (TileCal). The sources, propelled by a water-based liquid through tubes that traverse all the calorimeter's cells, produce signals that precisely characterise the response of each tile, thereby providing very granular and accurate…
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This article describes the design, construction and use of a calibration and monitoring system, based on movable 137Cs gamma-ray sources, for the ATLAS Tile Calorimeter (TileCal). The sources, propelled by a water-based liquid through tubes that traverse all the calorimeter's cells, produce signals that precisely characterise the response of each tile, thereby providing very granular and accurate data on the response of TileCal to particles. The system has been used to guide and control the quality of the optical instrumentation of all TileCal modules, to set and equalise the dynamic range of the response to physics data, and to set the energy scale of the readout system. In the ATLAS cavern, periodic measurements of the whole detector's response to 137Cs sources allow monitoring the uniformity and stability of all the calorimeter's cells as well as maintaining precise knowledge of its energy calibration. The design of the source hydraulic drive system's hardware and software, the data acquisition system and the data processing algorithms are described. Finally, the results of this two-decade program are shown.
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Submitted 28 February, 2020;
originally announced February 2020.
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Multimodal Plasmonics in Fused Colloidal Networks
Authors:
Alexandre Teulle,
M. Bosman,
C. Girard,
Kargal L. Gurunatha,
Mei Li,
Stephen Mann,
Erik Dujardin
Abstract:
Harnessing the optical properties of noble metals down to the nanometer-scale is a key step towards fast and low-dissipative information processing. At the 10-nm length scale, metal crystallinity and patterning as well as probing of surface plasmon (SP) properties must be controlled with a challenging high level of precision. Here, we demonstrate that ultimate lateral confinement and delocalizatio…
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Harnessing the optical properties of noble metals down to the nanometer-scale is a key step towards fast and low-dissipative information processing. At the 10-nm length scale, metal crystallinity and patterning as well as probing of surface plasmon (SP) properties must be controlled with a challenging high level of precision. Here, we demonstrate that ultimate lateral confinement and delocalization of SP modes are simultaneously achieved in extended self-assembled networks comprising linear chains of partially fused gold nanoparticles. The spectral and spatial distributions of the SP modes associated with the colloidal superstructures are evidenced by performing monochromated electron energy loss spectroscopy with a nanometer-sized electron probe. We prepare the metallic bead strings by electron beam-induced interparticle fusion of nanoparticle networks. The fused superstructures retain the native morphology and crystallinity but develop very low energy SP modes that are capable of supporting long range and spectrally tunable propagation in nanoscale waveguides.
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Submitted 17 September, 2014;
originally announced September 2014.
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A Layer Correlation technique for pion energy calibration at the 2004 ATLAS Combined Beam Test
Authors:
E. Abat,
J. M. Abdallah,
T. N. Addy,
P. Adragna,
M. Aharrouche,
A. Ahmad,
T. P. A. Akesson,
M. Aleksa,
C. Alexa,
K. Anderson,
A. Andreazza,
F. Anghinolfi,
A. Antonaki,
G. Arabidze,
E. Arik,
T. Atkinson,
J. Baines,
O. K. Baker,
D. Banfi,
S. Baron,
A. J. Barr,
R. Beccherle,
H. P. Beck,
B. Belhorma,
P. J. Bell
, et al. (460 additional authors not shown)
Abstract:
A new method for calibrating the hadron response of a segmented calorimeter is developed and successfully applied to beam test data. It is based on a principal component analysis of energy deposits in the calorimeter layers, exploiting longitudinal shower development information to improve the measured energy resolution. Corrections for invisible hadronic energy and energy lost in dead material in…
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A new method for calibrating the hadron response of a segmented calorimeter is developed and successfully applied to beam test data. It is based on a principal component analysis of energy deposits in the calorimeter layers, exploiting longitudinal shower development information to improve the measured energy resolution. Corrections for invisible hadronic energy and energy lost in dead material in front of and between the calorimeters of the ATLAS experiment were calculated with simulated Geant4 Monte Carlo events and used to reconstruct the energy of pions impinging on the calorimeters during the 2004 Barrel Combined Beam Test at the CERN H8 area. For pion beams with energies between 20 GeV and 180 GeV, the particle energy is reconstructed within 3% and the energy resolution is improved by between 11% and 25% compared to the resolution at the electromagnetic scale.
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Submitted 12 May, 2011; v1 submitted 20 December, 2010;
originally announced December 2010.
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ATLAS Detector Status and Physics Startup Plans
Authors:
Martine Bosman
Abstract:
The status of the ATLAS detector shortly before the start-up of the LHC is presented. The progress in the commissioning of the detector, as well as plans for early physics analysis are outlined.
The status of the ATLAS detector shortly before the start-up of the LHC is presented. The progress in the commissioning of the detector, as well as plans for early physics analysis are outlined.
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Submitted 17 October, 2008;
originally announced October 2008.