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Scanning probe microscopy and potentiometry using a junction field effect transistor based sensor
摘要： Scanning tunneling microscopy in its conventional form relies on a steady state tunneling current of 10?12–10?6 A. However, for various applications, it is desirable to reduce the current load to a minimum. Here, we present first experiments using a cooled junction field effect transistor in open gate operation, thereby reducing the DC-current to less than 10?19 A. This enables almost ideal measurements of the local electrochemical potential on a surface. Various methods applying dynamic modes can be used to maintain a constant distance between the scanning probe and the sample surface. Here, we use an AC-bias applied to the sample and a lock-in amplifier connected to the preamplifier to evaluate the conductance of the tunneling gap.
关键词： potentiometry,scanning probe microscopy,junction field effect transistor,sensor
更新于2025-09-09 09:28:46
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[Nanostructure Science and Technology] Nanowire Electronics || Properties Engineering of III–V Nanowires for Electronic Application
摘要： Semiconductors have been the core materials of many technological advances in recent years. Silicon, the most studied and used semiconducting material, has been the center of semiconductor industry for decades because it is available abundantly and easy to dope, and silicon dioxide is a superior dielectric material in microelectronic industry. This material can be used to make computer chips, optoelectronics devices, and solar cell. Silicon reshapes the way we live and is unarguably one of the most important materials in modern society. Through its dominant role in the semiconductor industry for now, the search for alternatives is fueled by the unstoppable demand for high-performance and low-power electronics. Among different kinds of semiconductors, III–V semiconductor holds promising properties for replacing silicon, and in particular, the NW structure of III–V semiconductor has been studied extensively.
关键词： nanowire field-effect transistor,semiconductors,contact engineering,crystal engineering,III–V nanowires,surface modification,electronic application
更新于2025-09-09 09:28:46
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Preparation and application of polystyrene-grafted alumina core-shell nanoparticles for dielectric surface passivation in solution-processed polymer thin film transistors
摘要： Polystyrene-grafted alumina nanoparticles were synthesized by silane coupling between dimethylchlorosilane-terminated polystyrene (PS) and gamma-type alumina nanoparticles and characterized. The surface grafting density of the polystyrene chains on the nanoparticles was estimated to be 0.13 molecules per square nanometer. The Al2O3-PS nanoparticles are solution processable in organic solvents, including ethyl acetate, butyl acetate, and toluene, which enabled preparation of blends with polystyrene or poly(methyl methacrylate). The dielectric constant of the Al2O3-PS nanoparticle/polymer blend films is composition tunable from 2.59 to 7.79. The alumina-PS nanoparticles and their blends with polymers were found to form efficient surface passivation films on the oxide dielectric layer in organic field-effect transistors (OFETs).
关键词： core-shell nanoparticle,alumina-polymer gate insulator,organic field-effect transistor,surface modification
更新于2025-09-09 09:28:46
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Catalyst-free synthesis of few-layer graphene films on silicon dioxide/Si substrates using ethylene glycol by chemical vapor deposition
摘要： Catalyst-free growth of graphene directly on dielectric substrates is a challenging work for graphene-based electronics. In this paper, a simple method to synthesize large area few layer graphene films on silicon dioxide/Si substrates by chemical vapor deposition is reported. A novel liquid carbon source (ethylene glycol) is used, without any catalysts. The obtained graphene films are characterized by Raman spectroscopy, X-ray photoelectron spectroscopy, atomic force microscopy. The field effect transistor with graphene film as channel material is fabricated, and the carrier mobility is 707 cm2/V.S. This work offers a new strategy to directly grow graphene on silicon dioxide/Si substrates, and the as-synthesized graphene films may have potential applications in sensors, conductive films, electronic devices, etc.
关键词： Field effect transistor,Synthesis,Catalyst-free,Graphene,Ethylene glycol
更新于2025-09-09 09:28:46
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Top-gated graphene field-effect transistors by low-temperature synthesized SiN <i> <sub/>x</sub></i> insulator on SiC substrates
摘要： Top-gated devices made from an epitaxial graphene film on a 4H-SiC substrate were fabricated. Atomic force microscopy and Raman spectroscopy results showed that a large-scale highly uniform monolayer graphene film was synthesized on the SiC substrate. A SiNx passivation film was deposited on a SiC graphene device as a top gate insulator by catalytic chemical-vapor deposition (Cat-CVD) below 65 °C. After the top gate electrode was formed on the SiNx film, no leakage current flowed between the gate and source electrodes. The transport characteristics showed clear ambipolar characteristics from 8 to 280 K, and the temperature dependences of the conductance and field-effect mobility of the devices implied that monolayer graphene devices can be successfully fabricated. Moreover, the position of the charge neutrality point after SiNx deposition was around 0 V, indicating p-doping characteristics. These results indicate that SiNx films synthesized by Cat-CVD can be used as gate insulators and that the carrier type may be controlled by adjusting the deposition conditions.
关键词： SiNx,Cat-CVD,field-effect transistors,graphene,SiC substrates
更新于2025-09-09 09:28:46
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The Role of Weak Molecular Dopants in Enhancing the Performance of Solution-Processed Organic Field-Effect Transistors
摘要： Molecular doping is an effective method to enhance the charge carrier density for reducing the contact resistance and improving the charge mobility in organic field-effect transistors (OFETs). Previous reports mainly focus on the strong dopants with the EAdopant > IEOSC (p-type) or IEdopant < EAOSC (n-type) to enable the efficient charge transfer (EA: electron affinity; IE: ionization energy; OSC: organic semiconductor). However, the effects of weak dopants on the OFET performance of OSC are rarely investigated. Thus, in this study, it is demonstrated that two new fluorinated compounds (Tetrafluorophthalonitrile (TFP) and Octafluoronaphthalene (OFN)) can act as weak dopants in thin film of TIPS-Pentacene (TIPS). Although they exhibit unmatched EAs (3.45 eV for TFP and 3.44 eV for OFN) compared to the IE (5.17 eV) of the host TIPS, they still can fulfill the p-type doping with the OSC matrix. Systematic structural and electrical characterization reveals the important role of the formed charge-transfer interaction and the improved crystallinity in enhancing the carrier mobility. The doped poly(3-hexylthiophene) is also investigated to confirm the universality of the weak dopants. The study should provide a new thought for the exploitation of novel planar soluble weak dopants in OFETs.
关键词： solution-processed organic field-effect transistors,molecular doping,weak dopants
更新于2025-09-09 09:28:46
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Monolayer-ReS2 field effect transistor using monolayer-graphene as electrodes
摘要： Atomic thinness, excellent transport property and gate-tunable band structure of graphene render it a potential electrode material for assembling ultra thin electronic devices. Here, we present back gate field effect transistor based on exfoliated monolayer (ML) ReS2 as channel semiconductor and exfoliated ML-graphene as drain-source electrodes. The G and 2D peaks of ML-graphene stiffen significantly and their intensity ratio increases as well when the graphene is encapsulated between the SiO2/Si substrate and ReS2. Owing to the excellent electron transport properties of the ML-ReS2 and gate-tunable Fermi-level of the underlying ML-graphene, the transistor exhibits on/off current ratio exceeding 106, mobility of ~1.1 cm2V-1s-1 and subthreshold swing ~740 mV per decade. This work indicates that ML-graphene is an excellent electrode material for fabricating atomically thin ReS2 electronic devices.
关键词： Field effect transistor,Graphene,2D materials,ReS2
更新于2025-09-09 09:28:46
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Ambipolar carrier transport in an optically controllable diarylethene thin film transistor
摘要： Ambipolar carrier transport is demonstrated in an optically controllable organic field-effect transistor, where a benzothienothiophene-substituted diarylethene (BTT-DAE) thin film is employed directly as the transistor channel. A closed-ring isomer, which is produced by ultraviolet (UV) light irradiation, allows the carrier injection of both holes and electrons from source-drain electrodes into the BTT-DAE layer. Moreover, alternate UV or visible (VIS) light irradiation induces marked switching in the drain currents caused by reversible photoisomerization between closed-ring (semiconductor) and open-ring (insulator) isomers. The light-driven on/off ratio, which is defined by the ratio of the drain currents in the sample after UV or VIS light irradiation, reaches 240 for hole transport. The value is comparable to the gate-voltage-induced on/off ratio of 160. Our findings, therefore, have a potential to lead to the construction of new optoelectronic devices such as photoreconfigurable logic circuits and light emitting transistors.
关键词： Ambipolar operation,Optical switching,Organic field-effect transistor,Diarylethene,Photochromism
更新于2025-09-09 09:28:46
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Substrate-Wide Confined Shear Alignment of Carbon Nanotubes for Thin Film Transistors
摘要： To exploit their charge transport properties in transistors, semiconducting carbon nanotubes must be assembled into aligned arrays comprised of individualized nanotubes at optimal packing densities. However, achieving this control on the wafer-scale is challenging. Here, solution-based shear in substrate-wide, confined channels is investigated to deposit continuous films of well-aligned, individualized, semiconducting nanotubes. Polymer-wrapped nanotubes in organic ink are forced through sub-mm tall channels, generating shear up to 10 000 s?1 uniformly aligning nanotubes across substrates. The ink volume and concentration, channel height, and shear rate dependencies are elucidated. Optimized conditions enable alignment within a ±32° window, at 50 nanotubes μm?1, on 10 × 10 cm2 substrates. Transistors (channel length of 1–5 μm) are fabricated parallel and perpendicular to the alignment. The parallel transistors perform with 7× faster charge carrier mobility (101 and 49 cm2 V?1 s?1 assuming array and parallel-plate capacitances, respectively) with high on/off ratio of 105. The spatial uniformity varies ±10% in density, ±2° in alignment, and ±7% in mobility. Deposition occurs within seconds per wafer, and further substrate scaling is viable. Compared to random networks, aligned nanotube films promise to be a superior platform for applications including sensors, flexible/stretchable electronics, and light emitting and harvesting devices.
关键词： electronics,alignment,mobility,field-effect transistors,semiconductors
更新于2025-09-09 09:28:46
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[IEEE 2018 IEEE International Conference on Electron Devices and Solid State Circuits (EDSSC) - Shenzhen (2018.6.6-2018.6.8)] 2018 IEEE International Conference on Electron Devices and Solid State Circuits (EDSSC) - Carrier Injection Mechanism of Metal-MoS<inf>2</inf> Ohmic Contact in MoS<inf>2</inf> FETs
摘要： In order to enhance the carrier injection of MoS2 field effect transistors (FETs,) understanding the injection mechanism of metal-MoS2 contacts is essential. In this work, MoS2 (FETs) with Ti and Sc electrodes were fabricated and characterized, respectively. The carrier injection mechanism was studied from the perspective of the tunneling models. With the narrower barrier width, the Sc-MoS2 contact shows a different injection mechanism from that of Ti-MoS2, making Sc a promising improvement as MoS2 FETs electrodes.
关键词： Ohmic contact,MoS2,tunneling,field effect transistor (FET)
更新于2025-09-09 09:28:46