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Site-controlled formation of single Si nanocrystals in a buried SiO <sub/>2</sub> matrix using ion beam mixing
摘要： For future nanoelectronic devices – such as room-temperature single electron transistors – the site-controlled formation of single Si nanocrystals (NCs) is a crucial prerequisite. Here, we report an approach to fabricate single Si NCs via medium-energy Si+ or Ne+ ion beam mixing of Si into a buried SiO2 layer followed by thermally activated phase separation. Binary collision approximation and kinetic Monte Carlo methods are conducted to gain atomistic insight into the influence of relevant experimental parameters on the Si NC formation process. Energy-filtered transmission electron microscopy is performed to obtain quantitative values on the Si NC size and distribution in dependence of the layer stack geometry, ion fluence and thermal budget. Employing a focused Ne+ beam from a helium ion microscope, we demonstrate site-controlled self-assembly of single Si NCs. Line irradiation with a fluence of 3000 Ne+/nm2 and a line width of 4 nm leads to the formation of a chain of Si NCs, and a single NC with 2.2 nm diameter is subsequently isolated and visualized in a few nanometer thin lamella prepared by a focused ion beam (FIB). The Si NC is centered between the SiO2 layers and perpendicular to the incident Ne+ beam.
关键词： phase separation,Monte Carlo simulations,single electron transistor,ion beam mixing,helium ion microscopy
更新于2025-11-21 11:20:48
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Highly sensitive and selective room-temperature NO2 gas-sensing characteristics of SnOX-based p-type thin-film transistor
摘要： The high-performance p-type metal-oxide-semiconductor (MOS)-based gas sensor is an important subject of research in the field of gas-sensing technology. In this work, we demonstrated a p-type MOS-based thin-film transistor (TFT) nitrogen dioxide (NO2) gas sensor that used tin oxide (SnOX) for both the channel and sensing layers. The crystalline status, surface morphology, and atomic-bonding configuration of the thin-film were examined using X-ray diffraction, field emission-scanning electron microscopy, and X-ray photoelectron spectroscopy. The results indicated that the deposited thin-film was mainly composed of polycrystalline SnO with a tetragonal structure. The fabricated p-type SnOX TFT showed a maximum response value of 19.4-10 ppm NO2 at room temperature (RT, 25 °C) when operated in the subthreshold region, which was significantly higher than that of 2.8–10 ppm NO2 obtained from a p-type SnOX thin-film chemiresistor at RT. In addition, the SnOX TFT gas sensor showed significantly higher sensitivity to NO2 gas than to other target gases such as NH3, H2S, CO2, and CO at RT. To the best of our knowledge, this is the first study to a p-type MOS-based field-effect transistor-type gas sensor. Our experimental results demonstrate that the p-type SnOX TFT is a promising gas sensor that can operate at RT with high sensitivity and selectivity to NO2 gas.
关键词： SnO,Thin-film transistor,NO2 gas sensing,SnOX,P-type metal oxide semiconductor
更新于2025-11-21 11:01:37
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Pyrene-SH functionalized OTFT for detection of Hg2+ ions in aquatic environments
摘要： Mercury ion (Hg2+) sensor based on bottom gate top contact organic thin film transistor (OTFT) was fabricated. The OTFT channel area was functionalized with pyrene that contain thiol group, which has strong binding affinity toward Hg2+ ion. The OTFT sensor exhibited a charge mobility of 0.28 cm2 V–1 s–1, a threshold voltage of -22.3 V and on-to-off ratio 103. The sensor shows high selectivity to Hg2+ ion over other two valence metal ions. OTFT sensor exhibited high sensitivity to Hg2+ ion, indicated by increasing of drain current after exposed to different concentration of Hg2+ ion ranging from 1 mM to 0.01 μM. Moreover, the OTFT sensor capability for practical application was also demonstrated by sensing the present of 25 μM of Hg2+ ion in tap, drinking and seawater samples.
关键词： Mercury sensor,Pyrene derivative,Organic thin film transistor
更新于2025-11-14 17:28:48
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Reduction of Bias and Light Instability of Mixed Oxide Thin-Film Transistors
摘要： Despite their potential use as pixel-switching elements in displays, the bias and light instability of mixed oxide semiconductor thin-film transistors (TFTs) still limit their application to commercial products. Lack of reproducible results due to the sensitivity of the mixed oxides to air exposure and chemical contamination during or after fabrication hinders any progress towards the achievement of stable performance. Consequently, one finds in literature several theories and mechanisms, all justified, but most of them conflict despite being on the same subject matter. In this study, we show that under an optimized fabrication process, which involves the in situ passivation of a mixed oxide semiconductor, we can reduce the bias and light instability of the mixed-oxide semiconductor TFTs by decreasing the semiconductor thickness. We achieve a negligible threshold voltage shift under negative bias combined with light illumination stress when the mixed oxide semiconductor thickness is around three nanometers. The improvement of stability in the thin mixed-oxide semiconductor TFTs is due to a reduced number of oxygen-vacancy defects in the bulk of the semiconductor, as their total number decreases with decreasing thickness. Under the optimized fabrication process, bulk, rather than interfacial defects, thus seem to be the main source of the bias and light instability in mixed oxide TFTs.
关键词： oxide,stability,thin film transistor
更新于2025-11-14 17:28:48
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Electronic transport in MoSe <sub/>2</sub> FETs modified by latent tracks created by swift heavy ion irradiation
摘要： Unique characteristics of transition metal dichalcogenides (TMDCs) such as their tunable band gap and ultra-thin body thickness make them potential candidates for applications in optoelectronic, gas sensing and energy storage devices. In this work, 1.8 GeV Ta ions at different ion fluences ranging from 1 × 109 ions cm?2 to 6 × 1010 ions cm?2 were used to introduce amorphous defective regions, latent tracks, in MoSe2 to study the electronic transport behavior in irradiated TMDC-channel field-effect transistors (FETs). Defects in these materials induced by the swift heavy ion irradiation play a vital role in the device applications. The results show that carrier mobility decreases while resistance of the devices increases abruptly with increasing ion fluences. The impact mechanism of the latent tracks on electronic transport behavior in TMDC-channel FETs was analyzed in detail. It was assumed that the Bloch wave of electrons was strongly localized by the latent tracks induced by the SHI irradiation and the Bloch wave of electrons can be scattered by the latent tracks as well. This study helps to investigate the influence of the latent tracks on electronic transport in other 2D materials as well.
关键词： latent track,field-effect transistor,molybdenum selenide,electronic transportation,swift heavy ion irradiation
更新于2025-11-14 17:03:37
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Stepped Annealed Inkjet-Printed InGaZnO Thin-Film Transistors
摘要： The preparation of thin-film transistors (TFTs) using ink-jet printing technology can reduce the complexity and material wastage of traditional TFT fabrication technologies. We prepared channel inks suitable for printing with different molar ratios of their constituent elements. Through the spin-coated and etching method, two different types of TFTs designated as depletion and enhancement mode were obtained simply by controlling the molar ratios of the InGaZnO channel elements. To overcome the problem of patterned films being prone to fracture during high-temperature annealing, a stepped annealing method is proposed to remove organic molecules from the channel layer and to improve the properties of the patterned films. The different interfaces between the insulation layers, channel layers, and drain/source electrodes were processed by argon plasma. This was done to improve the printing accuracy of the patterned InGaZnO channel layers, drain, and source electrodes, as well as to optimize the printing thickness of channel layers, reduce the defect density, and, ultimately, enhance the electrical performance of printed TFT devices.
关键词： thin-film transistor,annealing,plasma treatment,ink-jet printing
更新于2025-10-24 16:37:46
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Percolation Effects in Electrolytically-Gated WS <sub/>2</sub> /Graphene Nano:Nano Composites
摘要： Mixed networks of conducting and non-conducting nanoparticles show promise in a range of applications where fast charge transport is important. While the dependence of network conductivity on the conductive mass fraction (Mf) is well understood, little is known about the Mf-dependence of mobility and carrier density. This is particularly important as the addition of graphene might lead to increases in the mobility of semiconducting nanosheet-network transistors. Here, we use electrolytic gating to investigate the transport properties of spray-coated composite networks of graphene and WS2 nanosheets. As the graphene Mf is increased, we find both conductivity and carrier density to increase in line with percolation theory with percolation thresholds (~8 vol%) and exponents (~2.5) consistent with previous reporting. Perhaps surprisingly, we find the mobility increases modestly from ~0.1 cm2/Vs (for a WS2 network) to ~0.3 cm2/Vs (for a graphene network) which we attribute to the similarity between WS2-WS2 and graphene-graphene junction resistances. In addition, we find both the transistor on- and off-currents to scale with Mf according to percolation theory, changing sharply at the percolation threshold. Through fitting, we show that only the current in the WS2 network changes significantly upon gating. As a result, the on-off ratio falls sharply at the percolation threshold from ~104 to ~2 at higher Mf. Reflecting on these results, we conclude that the addition of graphene to a semiconducting network is not a viable strategy to improve transistor performance as it reduces the on:off ratio far more than it improves the mobility.
关键词： graphene,ionic liquid,thin film transistor,WS2,carrier density,composite,mobility,Printed electronics
更新于2025-10-22 19:40:53
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Maximizing the Current Output in Self-Aligned Graphene–InAs–Metal Vertical Transistors
摘要： With finite density of states and electrostatically tunable work function, graphene can function as a tunable contact for semiconductor channel to enable vertical field effect transistors (VFET). However, the overall performance, especially the output current density is still limited by the low conductance of the vertical semiconductor channel, as well as large series resistance of graphene electrode. To overcome these limitations, we construct a VFET by using single crystal InAs film as the high conductance vertical channel and self-aligned metal contact as the source-drain electrodes, resulting a record high current density over 45,000 A/cm2 at a low bias voltage of 1 V. Furthermore, we construct a device-level VFET model using resistor network method, and experimentally validate the impact of each geometry parameter on device performance. Importantly, we found the device performance is not only a function of intrinsic channel material, but also greatly influenced by device geometries and footprint. Our study not only pushes the performance limit of graphene VFETs, but also sheds light on van der Waals integration between two-dimensional material and conventional bulk material for high performance VFETs and circuits.
关键词： resistor network model,high current density,vertical transistor,graphene,van der Waals heterostructure,InAs film
更新于2025-09-23 15:23:52
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2D Material-Based Vertical Double Heterojunction Bipolar Transistors with High Current Amplification
摘要： The heterojunction bipolar transistor (HBT) differs from the classical homojunction bipolar junction transistor in that each emitter-base-collector layer is composed of a different semiconductor material. 2D material (2DM)-based heterojunctions have attracted attention because of their wide range of fundamental physical and electrical properties. Moreover, strain-free heterostructures formed by van der Waals interaction allows true bandgap engineering regardless of the lattice constant mismatch. These characteristics make it possible to fabricate high-performance heterojunction devices such as HBTs, which have been difficult to implement in conventional epitaxy. Herein, NPN double HBTs (DHBTs) are constructed from vertically stacked 2DMs (n-MoS2/p-WSe2/n-MoS2) using dry transfer technique. The formation of the two P–N junctions, base-emitter, and base-collector junctions, in DHBTs, was experimentally observed. These NPN DHBTs composed of 2DMs showed excellent electrical characteristics with highly amplified current modulation. These results are expected to extend the application field of heterojunction electronic devices based on various 2DMs.
关键词： 2D materials,tungsten diselenide,P–N junction,heterojunction bipolar transistor,molybdenum disulfide
更新于2025-09-23 15:23:52
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An optically-gated transistor comprised of amorphous M+Ge2Se3 (M=Cu, Sn) for accessing and continuously programming a memristor
摘要： We demonstrate that a device comprised of sputtered amorphous chalcogenide Ge2Se3/M+Ge2Se3 (M = Sn or Cu) alternating layers, functions as an optically-gated transistor (OGT) and can be used as an access transistor for a memristor memory element. This transistor has only two electrically connected terminals (source and drain), with the gate being optically controlled, thus allowing the transistor to operate only in the presence of light (385 – 1200 nm). The switching speed of the OGTs is less than 15 μs. The OGT is demonstrated in series with a Ge2Se3+W memristor, where we show that by altering the light intensity on the OGT gate, the memristor can be programmed to a continuous range of non-volatile memory states using the saturation current of the OGT as a programming compliance current. By having a continuous range of non-volatile states, one memory cell can potentially achieve 2n levels. This high density, combined with optical programmability, enables hybrid electronic/photonic memory.
关键词： access transistor,chalcogenide,resistive RAM,optoelectronic,selector,amorphous,memristor
更新于2025-09-23 15:23:52