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Investigation of the performance of strain-engineered silicon nanowire field effect transistors (?-Si-NWFET) on IOS substrates
摘要： In the current work, a design space for developing the performance enhanced strain-engineered Si nanowire field-effect-transistors has been provided. The fraction of insertion of the nanowire channel into the Insulator-on-Silicon substrate with judicious selection of high-k gate insulators is used as the key design parameter. The combined effect of fractional insertion and gate insulators results in inducing stress into the nanowire channel and, depending on their selection, it changes from tensile to compressive. Such induced-stress alters the existing inherent phononic-stress, leading to the modification of the carrier transport in the device channel. The carrier transport behavior in such partially embedded nanowire FETs has been modeled by incorporating the relevant stress-related effects into the indigenously developed self-consistent quantum-electrostatic framework. These equations are solved by employing the non-equilibrium Green’s function formalism. The study shows the phonon scattering under tensile strain to occur at the expense of electron energy; however, the electrons can also gain energy during such scattering in compressive stress. Thus, the device current has been observed to increase with tensile stress and it achieves relatively smaller values when the inherent tensile phononic stress is balanced by the induced compressive stress. However, the current is finally observed to increase once the compressive stress overcomes the inherent tensile phononic stress. In general, the present devices exhibit promising Ion/Ioff ratio for all of the fractional insertions and gate dielectrics with a maximum Ioff of <10 nA/μm, threshold voltage of sub-0.3 V, gm of ～104 μS/μm, sub-threshold swing of ～100 mV/dec, and drain-induced-barrier-lowering of ～100 mV/V.
关键词： IOS substrates,high-k gate insulators,strain-engineered,silicon nanowire,non-equilibrium Green’s function,quantum-electrostatic framework,field-effect transistors
更新于2025-09-10 09:29:36
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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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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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Stochastic Resonance in Bioinspired Electronic Device Using Polymer Field Effect Transistors
摘要： Stochastic resonance (SR) phenomenon is emerged in organic field effect transistors (OFETs) using π-conjugated polymer, where application of external noise to the OFET system enhances signal/information processing performance which is often found in biological systems. The channel conductivity of the OFET is slightly increased by spin-coating using heated semiconductor polymer solution with heated glass substrate. In order to improve frequency responses of OFET, optimal width of the gate electrode is explored. Furthermore, it turns out that scratching and removing semiconductor film outside the source-drain electrodes and the channel enhances the On-Off current ratio of the device. These fabrication processes lead to steeper nonlinearity on the IDS vs. VGS curve, resulting in emergence of SR, which is fingerprinted in increase of correlation value between input and output signals with increase of intensity of external noise.
关键词： Stochastic resonance,Polymer thin films,Organic semiconductors,Bioinspiration,Field effect transistors
更新于2025-09-09 09:28:46
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Dependence of Short-Channel Effects on Semiconductor Bandgap in Tunnel Field-Effect Transistors
摘要： Scaling down the bandgap is considered as an essential approach to enhance the performance of tunnel field-effect transistors (TFETs). Using two-dimensional simulations, this study examines the dependence of short-channel effects on the semiconductor bandgap in TFETs. It is shown that the short-channel effect is more severe with using lower bandgap materials although the supply voltage is scaled in parallel with the bandgap. For a given bandgap material, the short-channel effect can be well evaluated by the increase of drain-induced barrier thinning (DIBT) with decreasing the channel length. For different bandgap TFETs, however, their short-channel effects cannot be compared properly by comparing the DIBTs. Adequately considering the effect of bandgap on the TFET scalability is necessary in designing scaled integrated circuits.
关键词： drain-induced barrier thinning,tunnel field-effect transistors,DIBT,semiconductor bandgap,TFETs,short-channel effects
更新于2025-09-09 09:28:46
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Single crystal hybrid perovskite field-effect transistors
摘要： The fields of photovoltaics, photodetection and light emission have seen tremendous activity in recent years with the advent of hybrid organic-inorganic perovskites. Yet, there have been far fewer reports of perovskite-based field-effect transistors. The lateral and interfacial transport requirements of transistors make them particularly vulnerable to surface contamination and defects rife in polycrystalline films and bulk single crystals. Here, we demonstrate a spatially-confined inverse temperature crystallization strategy which synthesizes micrometre-thin single crystals of methylammonium lead halide perovskites MAPbX3 (X = Cl, Br, I) with sub-nanometer surface roughness and very low surface contamination. These benefit the integration of MAPbX3 crystals into ambipolar transistors and yield record, room-temperature field-effect mobility up to 4.7 and 1.5 cm2 V?1 s?1 in p and n channel devices respectively, with 104 to 105 on-off ratio and low turn-on voltages. This work paves the way for integrating hybrid perovskite crystals into printed, flexible and transparent electronics.
关键词： hybrid perovskites,field-effect transistors,single crystals,ambipolar transport,inverse temperature crystallization
更新于2025-09-09 09:28:46
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[ASME ASME 2015 International Mechanical Engineering Congress and Exposition - Houston, Texas, USA (Friday 13 November 2015)] Volume 10: Micro- and Nano-Systems Engineering and Packaging - Characterization of the Electronic Properties and Strain Sensitivity of Graphene Formed by C <sub/>2</sub> H <sub/>2</sub> Chemical Vapor Deposition
摘要： We succeed in synthesizing large-area single-layer graphene sheets with different grain size using C2H2 chemical vapor deposition process. Our graphene shows high uniformity and low sheet resistance to 1080Ω/□. By fabricating graphene-based field effect transistors (FETs), the relation between the nucleation density and the electronic properties of CVD graphene are investigated. We found that the nucleation density can severely affect the defects formation in graphene, leading to the change in the electronic properties of graphene. We also check the strain sensitivity of CVD graphene. The as-grown graphene/Cu film was fixed onto the SiO2/Si substrate with a double-sided tape. The strain device is fabricated directly on the graphene-coated Cu standard photolithography and reactive ion etching (RIE) process. Then the device is transferred onto a stretchable and flexible polydimethysiloxane (PDMS) substrate. By using a motorized stage, the piezoresistive properties of graphene-based strain sensors. The one-dimensional tensile test is performed to investigate the piezoresistive properties. A gauge factor 3.4 was achieved under the tensile deformation.
关键词： field effect transistors,chemical vapor deposition,strain sensitivity,graphene,C2H2
更新于2025-09-09 09:28:46
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Performance and Reliability Improvement under High Current Densities in Black Phosphorus Transistors by Interface Engineering
摘要： Few-layer Black phosphorus (BP) has recently emerged as a promising two-dimensional (2D) material for electronic and optoelectronic devices due to its high mobility and tunable bandgap. However, BP is known to have quick degradation and oxidize in ambient conditions by breaking of the P-P bonds. As a result, there is a growing need to encapsulate BP that avoids oxygen and water while retaining the high electric performance of the devices. Here we demonstrate a hydrophobic polymer encapsulation technique with improved thermal conductivity for high current density, which preserves the electrical properties of BP back-gate transistors compared to the commonly used Al2O3 encapsulation with improved mobility and minimal traps. The on-off ratio increases for more than an order of magnitude at room temperature and more than four orders of magnitude at cryogenic temperatures. High field transport shows the first systematic study on unprecedented breakdown characteristics up to -5.5 V for the 0.16 μm transistors with a high current of 1.2 mA/μm at 20 K. These discoveries open up a new way to achieve high-performance 2D semiconductors with significantly improved breakdown voltage, on-off ratios, and stability under ambient conditions for practical applications in electronic and optoelectronic devices.
关键词： encapsulation,polymer,Black phosphorus,high-field transport,field-effect transistors,breakdown voltage,reliability
更新于2025-09-04 15:30:14
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Structural basis for a naphthyl end-capped oligothiophene with embedded metallic nanoparticles for organic field-effect transistors
摘要： We report on the apparent structure of 5,500-bis(naphth-2-yl)-2,20:50,200-terthiophene (NaT3) in organic field-effect transistors (OFETs) with and without embedded silver nanoparticles. Using regular- and microbeam grazing incidence wide- and small-angle X-ray scattering, the device structure is characterized locally in the area with the embedded particles. The NaT3 thin film order is reduced and the found unit cell (a ? 25.7 A? , b ? 5.87 A? , c ? 8.03 A? , and b ? 98.9(cid:2)) differs significantly from the one reported in the bulk, but shows no significant change, when the particles corresponding to the crystal size are incorporated into the device structure. At the same time, the apparent thin film crystal sizes in OFETs are found to be similar with and without the embedded particles. In both cases, the carrier mobilities are of the order of 10(cid:3)4 cm2/(V s).
关键词： X-ray scattering,oligothiophene,organic field-effect transistors,silver nanoparticles,crystal structure
更新于2025-09-04 15:30:14