Tania Roy

Journal Article npj 2D Materials and Applications · December 1, 2024 In in-sensor image preprocessing, the sensed image undergoes low level processing like denoising at the sensor end, similar to the retina of human eye. Optoelectronic synapse devices are potential contenders for this purpose, and subsequent applications in ... Full text Cite

A 2D route to 3D computer chips.

Journal Article Nature · January 2024 Full text Cite

Graphene/MoS2/SiOx memristive synapses for linear weight update

Journal Article npj 2D Materials and Applications · December 1, 2023 Memristors for neuromorphic computing have gained prominence over the years for implementing synapses and neurons due to their nano-scale footprint and reduced complexity. Several demonstrations show two-dimensional (2D) materials as a promising platform f ... Full text Cite

A minireview on 2D materials-enabled optoelectronic artificial synaptic devices

Journal Article APL Materials · July 1, 2022 Two-dimensional (2D) layered materials exhibit many unique properties, such as near-atomic thickness, electrical tunability, optical tunability, and mechanical deformability, which are characteristically distinct from conventional materials. They are parti ... Full text Cite

Multiwavelength Optoelectronic Synapse with 2D Materials for Mixed-Color Pattern Recognition.

Journal Article ACS nano · July 2022 Neuromorphic visual systems emulating biological retina functionalities have enormous potential for in-sensor computing, with prospects of making artificial intelligence ubiquitous. Conventionally, visual information is captured by an image sensor, stored ... Full text Cite

Graphene-oxide interface for optoelectronic synapse application.

Journal Article Scientific reports · April 2022 Optoelectronic synapses combine the functionalities of a non-volatile memory and photodetection in the same device, paving the path for the realization of artificial retina systems which can capture, pre-process, and identify images on the same platform. G ... Full text Cite

MoS₂ Synapses with Ultra-low Variability and Their Implementation in Boolean Logic.

Journal Article ACS nano · February 2022 Brain-inspired computing enabled by memristors has gained prominence over the years due to the nanoscale footprint and reduced complexity for implementing synapses and neurons. The demonstration of complex neuromorphic circuits using conventional materials ... Full text Cite

The Artificial Intelligent Pixel (aiPixel)

Conference Proceedings of SPIE - The International Society for Optical Engineering · January 1, 2022 The Artificial Intelligent Pixel (aiPixel), a novel in-pixel neural network based on the deconstruction of traditional sensor pixels is presented for the first time for detection, processing and digitizing at the pixel resulting in overall data reduction, ... Full text Cite

Graphene Enhances Actin Filament Assembly Kinetics and Modulates NIH-3T3 Fibroblast Cell Spreading.

Journal Article International journal of molecular sciences · January 2022 Actin plays critical roles in various cellular functions, including cell morphogenesis, differentiation, and movement. The assembly of actin monomers into double-helical filaments is regulated in surrounding microenvironments. Graphene is an attractive nan ... Full text Cite

A SPICE compact model for forming-free, low-power graphene-insulator-graphene ReRAM technology

Journal Article Emergent Materials · August 1, 2021 Development of scalable, low-power resistive memory devices (ReRAM) can be crucial for energy efficient neural networks with enhanced compute-in-memory capability. Recent demonstrations show promise for graphene as an electrode material for ultra-low power ... Full text Cite

Semiconductor-to-metal transition in atomic layer deposition (ALD) of VO2 films using VCl4 and water

Journal Article Applied Physics Letters · June 28, 2021 The semiconductor-to-metal transition of vanadium dioxide (VO2) films is studied using temperature-dependent Raman, optical, and electrical measurements. The VO2 films are deposited via an atomic layer deposition (ALD) process using alternate pulses of van ... Full text Cite

Scalable Van der Waals Two-Dimensional PtTe₂ Layers Integrated onto Silicon for Efficient Near-to-Mid Infrared Photodetection.

Journal Article ACS applied materials & interfaces · April 2021 In recent years, there has been increasing interest in leveraging two-dimensional (2D) van der Waals (vdW) crystals for infrared (IR) photodetection, exploiting their unusual optoelectrical properties. Some 2D vdW materials with small band gap energies suc ... Full text Cite

Growing Perovskite Quantum Dots on Carbon Nanotubes for Neuromorphic Optoelectronic Computing

Journal Article Advanced Electronic Materials · January 1, 2021 Brain-inspired (neuromorphic) computing that offers lower energy consumption and parallelism (simultaneous processing and memorizing) compared to von Neumann computing provides excellent opportunities in many computational tasks ranging from image recognit ... Full text Cite

CHAPTER 12: Ambipolar Inorganic Two-dimensional Materials for Solar Cells

Chapter · January 1, 2021 Ambipolar material refers to a class of materials that can transport both types of charged carriers, electrons and holes. This unique property allows the ambipolar materials to be used as either hole transport layers or electron transport layers or both, a ... Full text Cite

Optoelectronic synapse using monolayer MoS₂ field effect transistors.

Journal Article Scientific reports · December 2020 Optical data sensing, processing and visual memory are fundamental requirements for artificial intelligence and robotics with autonomous navigation. Traditionally, imaging has been kept separate from the pattern recognition circuitry. Optoelectronic synaps ... Full text Cite

Two-Dimensional Near-Atom-Thickness Materials for Emerging Neuromorphic Devices and Applications

Journal Article iScience · November 20, 2020 Two-dimensional (2D) layered materials and their heterostructures have recently been recognized as promising building blocks for futuristic brain-like neuromorphic computing devices. They exhibit unique properties such as near-atomic thickness, dangling-bo ... Full text Cite

Artificial Nociceptor Using 2D MoS2Threshold Switching Memristor

Journal Article IEEE Electron Device Letters · September 1, 2020 An artificial nociceptor realized with a single 2D MoS2-based memristor device is demonstrated in this work. The threshold switching memristor (TSM) device exhibits volatile resistance switching characteristics with low threshold voltage and a high ON-OFF ... Full text Cite

2D MoS2-Based Threshold Switching Memristor for Artificial Neuron

Journal Article IEEE Electron Device Letters · June 1, 2020 In this work, we use a two-terminal 2D MoS2-based memristive device to emulate an artificial neuron. The Au/MoS2/Ag device exhibits volatile resistance switching characteristics with a low threshold voltage and a high ON-OFF ratio of 106, originating from ... Full text Cite

Thickness-Independent Semiconducting-to-Metallic Conversion in Wafer-Scale Two-Dimensional PtSe₂ Layers by Plasma-Driven Chalcogen Defect Engineering.

Journal Article ACS applied materials & interfaces · March 2020 Platinum diselenide (PtSe2) is an emerging class of two-dimensional (2D) transition-metal dichalcogenide (TMD) crystals recently gaining substantial interest, owing to its extraordinary properties absent in conventional 2D TMD layers. Most inter ... Full text Cite

Ultrasensitive and ultrathin phototransistors and photonic synapses using perovskite quantum dots grown from graphene lattice.

Journal Article Science advances · February 2020 Organic-inorganic halide perovskite quantum dots (PQDs) constitute an attractive class of materials for many optoelectronic applications. However, their charge transport properties are inferior to materials like graphene. On the other hand, the charge gene ... Full text Cite

Electronic synapses with near-linear weight update using MoS2/graphene memristors

Journal Article Applied Physics Letters · September 2, 2019 Emulating the human brain's circuitry composed of neurons and synapses is an emerging area of research in mitigating the "von Neumann bottleneck" in present computer architectures. The building block of these neuromorphic systems-the synapse-is commonly re ... Full text Cite

Two-Dimensional/Three-Dimensional Schottky Junction Photovoltaic Devices Realized by the Direct CVD Growth of vdW 2D PtSe₂ Layers on Silicon.

Journal Article ACS applied materials & interfaces · July 2019 Two-dimensional (2D) platinum diselenide (PtSe2) layers are a new class of near-atom-thick 2D crystals in a van der Waals-assembled structure similar to previously explored many other 2D transition-metal dichalcogenides (2D TMDs). They exhibit d ... Full text Cite

Total-Ionizing-Dose Response of MoS2 Transistors With ZrO2 and h-BN Gate Dielectrics

Journal Article IEEE Transactions on Nuclear Science · July 1, 2019 The total-ionizing-dose response of few layer MoS2 transistors with ZrO2 or h-BN gate dielectrics is investigated under various bias conditions. Defects in MoS2 and surrounding dielectric layers significantly affect radiation-induced trapping. For devices ... Full text Cite

Artificial Neuron using Ag/2D-MoS/Au Threshold Switching Memristor

Conference Device Research Conference - Conference Digest, DRC · June 1, 2019 The phenomenal evolution of information and communication drives future technologies towards highly parallel, energy-efficient self-learning systems like the human brain. The limitations of current von Neumann computation systems have paved the way for art ... Full text Cite

Linear Weight Update in MoS/Graphene Memristive Synapses for Unsupervised Learning

Conference Device Research Conference - Conference Digest, DRC · June 1, 2019 Memristive synaptic devices are considered one of the most promising candidates for brain-inspired neuromorphic computing, owing to their decreased complexity and nanoscale footprint compared to conventional complementary metal oxide semiconductor (CMOS) c ... Full text Cite

Scaled dielectrics for scaled devices

Journal Article Nature Electronics · June 1, 2019 Ultrathin calcium fluoride layers can provide an effective gate dielectric for two-dimensional transistors. ... Full text Cite

Novel mesoporous electrode materials for symmetric, asymmetric and hybrid supercapacitors.

Journal Article Nanotechnology · May 2019 Electrochemical capacitors or supercapacitors have achieved great interest in the recent past due to their potential applications ranging from microelectronic devices to hybrid electric vehicles. Supercapacitors can provide high power densities but their i ... Full text Cite

A leaf-inspired photon management scheme using optically tuned bilayer nanoparticles for ultra-thin and highly efficient photovoltaic devices

Journal Article Nano Energy · April 1, 2019 We present a leaf-inspired biomimetic omnidirectional photon management scheme for ultrathin flexible graphene silicon Schottky junction solar cell. An all-dielectric approach comprising lossless spheroidal silica and titania nanoparticle bilayers is used ... Full text Cite

Artificial Neuron using Vertical MoS₂/Graphene Threshold Switching Memristors.

Journal Article Scientific reports · January 2019 With the ever-increasing demand for low power electronics, neuromorphic computing has garnered huge interest in recent times. Implementing neuromorphic computing in hardware will be a severe boost for applications involving complex processes such as image ... Full text Cite

The Role of Graphene and Other 2D Materials in Solar Photovoltaics.

Journal Article Advanced materials (Deerfield Beach, Fla.) · January 2019 2D materials have attracted considerable attention due to their exciting optical and electronic properties, and demonstrate immense potential for next-generation solar cells and other optoelectronic devices. With the scaling trends in photovoltaics moving ... Full text Cite

Uniform Vapor-Pressure-Based Chemical Vapor Deposition Growth of MoS₂ Using MoO₃ Thin Film as a Precursor for Coevaporation.

Journal Article ACS omega · December 2018 Chemical vapor deposition (CVD) is a powerful method employed for high-quality monolayer crystal growth of 2D transition metal dichalcogenides with much effort invested toward improving the growth process. Here, we report a novel method for CVD-based growt ... Full text Cite

Centimeter-Scale Periodically Corrugated Few-Layer 2D MoS₂ with Tensile Stretch-Driven Tunable Multifunctionalities.

Journal Article ACS applied materials & interfaces · September 2018 Two-dimensional (2D) transition metal dichalcogenide (TMD) layers exhibit superior optical, electrical, and structural properties unattainable in any traditional materials. Many of these properties are known to be controllable via external mechanical input ... Full text Cite

Artificial Neuron using MoS2/graphene threshold switching memristors

Conference Device Research Conference - Conference Digest, DRC · August 20, 2018 With the ever-increasing demand for low power electronics, neuromorphic computing has garnered huge interest in recent times. Artificial neurons form a critical part in neuromorphic circuits, and have been realized with complex CMOS circuitry in the past. ... Full text Cite

High quality gate dielectric/MoS2 interfaces probed by the conductance method

Journal Article Applied Physics Letters · June 4, 2018 Two-dimensional materials provide a versatile platform for various electronic and optoelectronic devices, due to their uniform thickness and pristine surfaces. We probe the superior quality of 2D/2D and 2D/3D interfaces by fabricating molybdenum disulfide ... Full text Cite

Centimeter-Scale 2D van der Waals Vertical Heterostructures Integrated on Deformable Substrates Enabled by Gold Sacrificial Layer-Assisted Growth.

Journal Article Nano letters · October 2017 Two-dimensional (2D) transition metal dichalcogenides (TMDs) such as molybdenum or tungsten disulfides (MoS2 or WS2) exhibit extremely large in-plane strain limits and unusual optical/electrical properties, offering unprecedented oppo ... Full text Cite

Air-Stable n-Doping of WSe2 by Anion Vacancy Formation with Mild Plasma Treatment

Journal Article ACS Nano · July 26, 2016 Transition metal dichalcogenides (TMDCs) have been extensively explored for applications in electronic and optoelectronic devices due to their unique material properties. However, the presence of large contact resistances is still a fundamental challenge i ... Full text Cite

2D-2D tunneling field-effect transistors using WSe2/SnSe2 heterostructures

Journal Article Applied Physics Letters · February 22, 2016 Two-dimensional materials present a versatile platform for developing steep transistors due to their uniform thickness and sharp band edges. We demonstrate 2D-2D tunneling in a WSe2/SnSe2 van der Waals vertical heterojunction device, where WSe2 is used as ... Full text Cite

Dual-gated MoS2/WSe2van der Waals tunnel diodes and transistors

Journal Article ACS Nano · February 24, 2015 Two-dimensional layered semiconductors present a promising material platform for band-to-band-tunneling devices given their homogeneous band edge steepness due to their atomically flat thickness. Here, we experimentally demonstrate interlayer band-to-band ... Full text Cite

2D layered materials: From materials properties to device applications

Conference Technical Digest - International Electron Devices Meeting, IEDM · February 16, 2015 An overview of material properties and the current state of electronic devices based on 2D layered materials is presented. Atomic scale smoothness, varying band alignment and sizeable bandgaps in the single layer limit make this class of materials very int ... Full text Cite

Engineering light outcoupling in 2D materials

Journal Article Nano Letters · February 11, 2015 When light is incident on 2D transition metal dichalcogenides (TMDCs), it engages in multiple reflections within underlying substrates, producing interferences that lead to enhancement or attenuation of the incoming and outgoing strength of light. Here, we ... Full text Cite

Field-effect transistors built from all two-dimensional material components

Journal Article ACS Nano · June 24, 2014 We demonstrate field-effect transistors using heterogeneously stacked two-dimensional materials for all of the components, including the semiconductor, insulator, and metal layers. Specifically, MoS2 is used as the active channel material, hexagonal-BN as ... Full text Cite

Cleaning graphene with a titanium sacrificial layer

Journal Article Applied Physics Letters · June 2, 2014 Graphene is a promising material for future electronic applications and chemical vapor deposition of graphene on copper is a promising method for synthesizing graphene on the wafer scale. The processing of such graphene films into electronic devices introd ... Full text Cite

Tunneling characteristics in chemical vapor deposited graphene-hexagonal boron nitride-graphene junctions

Journal Article Applied Physics Letters · March 24, 2014 Large area chemical vapor deposited graphene and hexagonal boron nitride was used to fabricate graphene-hexagonal boron nitride-graphene symmetric field effect transistors. Gate control of the tunneling characteristics is observed similar to previously rep ... Full text Cite

Nonlinear switching with ultralow reset power in graphene-insulator- graphene forming-free resistive memories

Journal Article IEEE Electron Device Letters · January 1, 2014 A high-performance resistive random access memory with graphene top and bottom electrodes and TiOx/Al2O3/TiO2 dielectric stacks is reported. The devices exhibit forming-free switching with stable operation at sub-μA operating current. The switching is high ... Full text Cite

Gate bias dependence of defect-mediated hot-carrier degradation in GaN HEMTs

Journal Article IEEE Transactions on Electron Devices · January 1, 2014 Monte Carlo analysis of hot-electron degradation in AlGaN/GaN high-electron mobility transistors shows that, for gate voltages corresponding to semi-ON bias conditions, the average electron energy has a spatial peak with 〈EAVE〉∼1.5 eV. The peak is located ... Full text Cite

Forming-free resistive switching with low current operation in graphene-insulator-graphene structures

Conference Device Research Conference - Conference Digest, DRC · December 16, 2013 Full text Cite

Integration and characterization of graphene-insulator-graphene junctions

Conference ECS Transactions · October 21, 2013 Graphene-insulator-graphene tunnel junctions have been fabricated and characterized. The cleaning processes for chemical vapor deposited graphene and integration of barrier engineered atomic layer deposited tunnel dielectrics is presented. Initial results ... Full text Cite

Temperature dependence and postirradiation annealing response of the 1/f noise of 4H-SiC MOSFETs

Journal Article IEEE Transactions on Electron Devices · July 15, 2013 The temperature dependence of the low-frequency noise of 4H-silicon carbide (SiC) MOSFETs with nitrided oxides is reported over the temperature range 85-510 K. The 1f noise decreases significantly with increasing measurement temperature. This decrease in n ... Full text Cite

Barrier engineering for double layer CVD graphene tunnel FETs

Journal Article Microelectronic Engineering · May 1, 2013 Atomic layer deposited high-k dielectrics with sputtered TiOx as the seeding layer have been explored for double layer graphene tunnel transistors. The subthreshold swing of these transistors is <100 mV/decade. Temperature-dependent measurements indicate d ... Full text Cite

Oxygen-related border traps in MOS and GaN devices

Conference ICSICT 2012 - 2012 IEEE 11th International Conference on Solid-State and Integrated Circuit Technology, Proceedings · December 1, 2012 Oxygen-related border traps cause low-frequency excess (1/f) noise in MOS transistors with SiO2 gate dielectrics and GaN/AlGaN HEMTs. In each case, the noise is associated with a reconfiguration of the microstructure of near-interfacial defects upon charge ... Full text Cite

Reliability of III-V devices - The defects that cause the trouble

Conference Microelectronic Engineering · February 1, 2012 Degradation of electronic devices by hot electrons is universally attributed to the generation of defects, but the mechanisms for defect generation and the specific nature of the pertinent defects are not known for most systems. Here we describe three rece ... Full text Cite

Room-temperature diffusive phenomena in semiconductors: The case of AlGaN

Journal Article Physical Review B - Condensed Matter and Materials Physics · December 20, 2011 Diffusion mediated by native point defects does not generally occur in semiconductors at room temperature (RT) because of high activation energies. However, recently observed plastic deformation in AlGaN/GaN structures in the presence of strain and electri ... Full text Cite

Radiation-induced defect evolution and electrical degradation of AlGaN/GaN high-electron-mobility transistors

Conference IEEE Transactions on Nuclear Science · December 1, 2011 Threshold-voltage shifts and increases in 1/f noise are observed in proton-irradiated AlGaN/GaN high-electron-mobility transistors, indicating defect-mediated device degradation. Quantum mechanical calculations demonstrate that low-energy recoils caused by ... Full text Cite

Temperature-dependence and microscopic origin of low frequency 1/f noise in GaN/AlGaN high electron mobility transistors

Journal Article Applied Physics Letters · November 14, 2011 We have performed low frequency 1/f noise measurements from 85 K to 450 K to investigate the energy distribution of defects in GaN/AlGaN high electron mobility transistors fabricated in three different processes. The noise is well described by the model of ... Full text Cite

Reliability-limiting defects in AlGaN/GaN HEMTs

Conference IEEE International Reliability Physics Symposium Proceedings · June 23, 2011 Low-frequency noise measurements and density functional theory calculations are combined to show that N-anti-site and C impurity defects can lead to changes in the low frequency noise of GaN/AlGaN HEMTs fabricated with three typical process conditions. Imp ... Full text Cite

1/f Noise in GaN HEMTs grown under Ga-rich, N-rich, and NH3-rich conditions

Conference Microelectronics Reliability · February 1, 2011 The magnitude of the low-frequency 1/f noise in GaN/AlGaN HEMTs grown under Ga-rich, N-rich, and NH3-rich conditions varies in response to hot-electron stress. Density-functional-theory (DFT) calculations show that the Ga vacancies that are responsible for ... Full text Cite

Dehydrogenation of defects and hot-electron degradation in GaN high-electron-mobility transistors

Journal Article Journal of Applied Physics · February 1, 2011 Degradation mechanisms limiting the electrical reliability of GaN high-electron-mobility transistors (HEMTs) are generally attributed to defect generation by hot-electrons but specific mechanisms for such processes have not been identified. Here we give a ... Full text Cite

Process dependence of proton-induced degradation in GaN HEMTs

Conference IEEE Transactions on Nuclear Science · December 1, 2010 The 1.8-MeV proton radiation responses are compared for AlGaN/GaN HEMTs grown under Ga-rich, N-rich, and NH3-rich conditions. The NH 3-rich devices are more susceptible to proton irradiation than the Ga-rich and N-rich devices. The 1/f noise of the devices ... Full text Cite

Electrical-stress-induced degradation in AlGaN/GaN high electron mobility transistors grown under gallium-rich, nitrogen-rich, and ammonia-rich conditions

Journal Article Applied Physics Letters · April 12, 2010 We have evaluated the long-term electrical reliability of GaN/AlGaN high-electron-mobility transistors grown under Ga-rich, N-rich, and NH 3 -rich conditions. Vpinch-off shifts positively after stress for devices grown under Ga-rich and N-rich conditions, ... Full text Cite

Single event mechanisms in 90 nm triple-well CMOS devices

Conference IEEE Transactions on Nuclear Science · December 1, 2008 Single event charge collection mechanisms in 90 nm triple-well NMOS devices are explained and compared with those of dual-well devices. The primary factors affecting the single event pulse width in triple-well NMOSFETs are the separation of deposited charg ... Full text Cite