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- 实验方案
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Gate-Tunable Thermal Metal–Insulator Transition in VO <sub/>2</sub> Monolithically Integrated into a WSe <sub/>2</sub> Field-Effect Transistor
摘要： Vanadium dioxide (VO2) shows promise as a building block of switching and sensing devices because it undergoes an abrupt metal-insulator transition (MIT) near room temperature, where the electrical resistivity changes by orders of magnitude. A challenge for versatile applications of VO2 is to control the MIT by gating in the field-effect device geometry. Here, we demonstrate a gate-tunable abrupt switching device based on a VO2 microwire that is monolithically integrated with a two-dimensional (2D) tungsten diselenide (WSe2) semiconductor by van der Waals stacking. We fabricated the WSe2 transistor using the VO2 wire as the drain contact, titanium as the source contact, and hexagonal boron nitride as the gate dielectric. The WSe2 transistor was observed to show ambipolar transport, with higher conductivity in the electron branch. The electron current increases continuously with gate voltage below the critical temperature of the MIT of VO2. Near the critical temperature, the current shows an abrupt and discontinuous jump at a given gate voltage, indicating that the MIT in the contacting VO2 is thermally induced by gate-mediated self-heating. Our results have paved the way for the development of VO2-based gate-tunable devices by the van der Waals stacking of 2D semiconductors, with great potential for electronic and photonic applications.
关键词： 2D materials,field-effect transistor,tungsten diselenide,phase-change materials,vanadium dioxide,metal-insulator transition,van der Waals heterostructures
更新于2025-09-23 15:22:29
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Graphene field-effect transistors with high extrinsic fT and fmax
摘要： In this work, we report on the performance of graphene field-effect transistors (GFETs) in which the extrinsic transit frequency (fT) and maximum frequency of oscillation (fmax) showed improved scaling behavior with respect to the gate length (Lg). This improvement was achieved by the use of high-quality graphene in combination with successful optimization of the GFET technology, where extreme low source/drain contact resistances were obtained together with reduced parasitic pad capacitances. GFETs with gate lengths ranging from 0.5 μm to 2 μm have been characterized, and extrinsic fT and fmax frequencies of up to 34 GHz and 37 GHz, respectively, were obtained for GFETs with the shortest gate lengths. Simulations based on a small-signal equivalent circuit model are in good agreement with the measured data. Extrapolation predicts extrinsic fT and fmax values of approximately 100 GHz at Lg=50 nm. Further optimization of the GFET technology enables fmax values above 100 GHz, which is suitable for many millimeter wave applications.
关键词： field-effect transistor,scaling,graphene,maximum frequency of oscillation,transit frequency
更新于2025-09-23 15:22:29
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Tertiary Amines Differentiated from Primary and Secondary Amines by Active Ester-Functionalized Hexabenzoperylene in Field Effect Transistors
摘要： Herein, we report two novel derivatives of hexabenzoperylene (HBP) that are functionalized with ester groups. Methyl acetate functionalized HBP (1) in single crystals self-assembles into a supramolecular nanosheet, which has a two-dimensional π-stack of HBP sandwiched between two layers of ester groups. With the same self-assembly motif, active ester-functionalized HBP (2) in field effect transistors has enabled differentiation of tertiary amines from primary and secondary amines, in agreement with the fact that active ester reacts with primary and secondary amines but not with tertiary amines to form amides.
关键词： sensors,organic field effect transistors,organic semiconductors,self-assembly,arenes
更新于2025-09-23 15:22:29
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Wafer-scale transferred multilayer MoS2 for high performance field effect transistors
摘要： Chemical vapour deposition (CVD) synthesis of semiconducting transition metal dichalcogenides (TMDs) offers a new route to build next-generation semiconductor devices. But realization of continuous and uniform multilayer (ML) TMD films is still limited by their specific growth kinetics, such as the competition between surface and interfacial energy. In this work, a layer-by-layer vacuum stacking transfer method is applied to obtain uniform and non-destructive ML-MoS2 films. Back-gated field effect transistors (FET) arrays of 1L- and 2L-MoS2 are fabricated on the same wafer, and their electrical performances are compared. We observe a significant increase of field-effect mobility for 2L-MoS2 FETs, up to 32.5 cm2V-1s-1, which is 7 times higher than that of 1L-MoS2 (4.5 cm2V-1s-1). Then we also fabricated 1L-, 2L-, 3L-, and 4L-MoS2 FETs to further investigate the thickness dependent characteristics of transferred ML-MoS2. Measurement results show a higher mobility but a smaller current on/off ratio as the number of layer increases, suggesting that a balance between mobility and current on/off ratio can be achieved in 2L- and 3L-MoS2 FETs. Dual-gated structure is also investigated to demonstrate an improved electrostatic control of the ML-MoS2 channel.
关键词： Field effect transistors,Transfer,CVD growth,2D materials,MoS2
更新于2025-09-23 15:22:29
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Distributed Amplifier Based on Monolayer Graphene Field Effect Transistor
摘要： Due to the ultra-high carrier mobility and ultralow resistivity of Graphene channel, a Graphene field effect transistor (GFET) is an interesting candidate for future RF and microwave electronics. In this paper, the introduction and review of existing compact circuit-level model of GFETs are presented. A compact GFET model based on drift-diffusion transport theory is then implemented in Verilog-A for RF/microwave circuit analysis. Finally, the GFET model is used to design a GFET-based distributed amplifier (DA) using advanced design system (ADS) tools. The simulation results demonstrate a gain of 8dB, an input/output return loss less than ?10dB, -3dB bandwidth from DC up to 5GHz and a dissipation of about 60.45mW for a 1.5V power supply. The main performance characteristics of the distributed amplifier are compared with 0.18μm CMOS technology.
关键词： Microwave,ADS,Distributed Amplifier (DA),Graphene Field Effect Transistor (GFET)
更新于2025-09-23 15:22:29
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A Surface Potential Based Model for Dual Gate Bilayer Graphene Field Effect Transistor Including the Capacitive Effects
摘要： In this work, a surface potential modeling approach has been proposed to model dual gate, bilayer graphene field effect transistor. The equivalent capacitive network of GFET has been improved considering the quantum capacitance effect for each layer and inter-layer capacitances. Surface potentials of both layers are determined analytically from equivalent capacitive network. The explicit expression of drain to source current is established from drift-diffusion transport mechanism using the surface potentials of the layers. The drain current characteristics and transfer characteristics of the developed model shows good agreement with the experimental results in literatures. The small signal parameters of intrinsic graphene transistor i.e. output conductance (gds), trans-conductance (gm), gate to drain capacitance (Cgd) and gate to source capacitance (Cgs) have been derived and finally, the cut-off frequency is determined for the developed model. The model is compared with reported experimental data using Normalised Root Mean Square Error (NRMSE) metric and it shows less than 16% NRMSE. A Verilog-A code has been developed for this model and a single ended frequency doubler has been designed in Cadence design environment using this Verilog-A model.
关键词： model,Field-effect transistor (FET),Verilog-A,Graphene,surface potential,frequency doubler.
更新于2025-09-23 15:22:29
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Improved Transistor Performance by Modulating Molecular Packing with Donor and Acceptor Moieties
摘要： The joint of the donor and acceptor moieties allows a facile and effective strategy to develop novel organic conjugated materials. However, few works report the understanding of the donor-acceptor interactions at the molecular level. Herein, we develop three small molecules contain one acceptor motif with different amounts of the donor unit. By the combination of theoretical calculation and energy level characterization, the lowest occupied molecular orbital (LUMO) levels of the three molecules were proven to be almost identical. The molecular packing modes were evaluated from crystal structure prediction. Due to the donor-acceptor interactions, the packing mode can be tuned from the 1D slipped stacking to the 2D brick layer. The 2D molecular packing and charge transport channel endowed the materials a higher electron mobility of 3.29 cm2 V?1 s?1 in the single-crystal field-effect transistors after such modulation.
关键词： organic field-effect transistor,conjugated molecules,donor-acceptor,crystal structure prediction
更新于2025-09-23 15:22:29
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Trap and 1/f-noise effects at the surface and core of GaN nanowire gate-all-around FET structure
摘要： Using capacitance, conductance and noise measurements, we investigate the trapping behavior at the surface and in the core of triangular-shaped one-dimensional (1D) array of GaN nanowire gate-all-around field effect transistor (GAA FET), fabricated via a top-down process. The surface traps in such a low dimensional device play a crucial role in determining the device performance. The estimated surface trap density rapidly decreases with increasing frequency, ranging from 6.07 × 1012 cm?2·eV?1 at 1 kHz to 1.90 × 1011 cm?2·eV?1 at 1 MHz, respectively. The noise results reveal that the power spectral density increases with gate voltage and clearly exhibits 1/f-noise signature in the accumulation region (Vgs > Vth = 3.4 V) for all frquencies. In the surface depletion region (1.5 V < Vgs < Vth), the device is governed by 1/f at lower frequencies and 1/f 2 noise at frequencies higher than ~ 5 kHz. The 1/f 2 noise characteristics is attributed to additional generation–recombination (G–R), mostly caused by the electron trapping/detrapping process through deep traps located in the surface depletion region of the nanowire. The cutoff frequency for the 1/f 2 noise characteristics further shifts to lower frequency of 102–103 Hz when the device operates in deep-subthreshold region (Vgs < 1.5 V). In this regime, the electron trapping/detrapping process through deep traps expands into the totally depleted nanowire core and the G–R noise prevails in the entire nanowire channel.
关键词： gate-all-around field effect transistor (FET),trap,nanowire,GaN,1/f-noise
更新于2025-09-23 15:22:29
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Tunable Schottky barriers in ultrathin black phosphorus field effect transistors via polymer capping
摘要： It is still a great challenge to avoid the degradation of ultrathin black phosphorus (BP) since its discovery in 2014. Various methods have been explored to stabilize the properties of ultrathin BP through capping technology or chemical passivation. Besides, the large metal-semiconductor contact resistance is also one of the critical issues. The two problems hinder the further development of ultrathin BP devices. Herein, we demonstrate that polymethyl methacrylate (PMMA) capping can not only enhance the durability of the ultrathin BP effectively and nondestructively, but also tune the effective Schottky barriers (SBs) formed at the interfaces between the metal and semiconductor dramatically. Particularly, the Schottky barrier (SB) for electron injection from metal to semiconductor is decreased by ~ 13 meV and the performance of the BP field effect transistor (FET) is strongly enhanced with the current on/off ratio increased by 6.8 times for the hole conduction after the PMMA capping. In addition, after the electron beam irradiation to the PMMA layer, the charge neutral point of the BP FET exhibits remarkable negative shift resulting in the electron dominated semiconductor channel at zero gate voltage. Furthermore, through partially capping the BP channel, a prototype of BP p-n diode was demonstrated with a maximum rectification factor of 21.3. The diode performs quite well with just a quarter of the BP channel capped by the PMMA layer. Our findings suggest that the PMMA capped ultrathin BP would be a promising choice for future device applications.
关键词： PMMA capping,ambipolar field effect transistor,ultrathin black phosphorus,Schottky barrier
更新于2025-09-23 15:22:29
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Effect of the length of a symmetric branched side chain on charge transport in thienoisoindigo-based polymer field-effect transistors
摘要： Compounds consisting of the electron-accepting thienoisoindigo (TIIG) moiety with branched alkyl side chains of various lengths were each copolymerized with thiophenylene vinylene thiophene (TVT) and selenophenylene vinylene selenophene (SVS) donor moieties, to investigate how the length of the side chain between the branch point and backbone affects the microstructure and charge transport of thin films made of these TIIGTVT and TIIGSVS copolymers. All of the organic field-effect devices based on these copolymers exhibited p-type behaviors, and these devices displayed hole mobility values as high as 1.15 cm2/V/s. Interestingly, the longer side chains in both series of TIIGTVT and TIIGSVS copolymers, the more improved was the molecular ordering of the thin films. But the relationship between charge mobility and side chain length differed for these two series of copolymers, a result attributed to differences between the microstructures of their films. The TIIGTVT series showed localized aggregation, with the greater length of the side chain between the branch point and backbone enhancing the charge transport by increasing the quantity and average size of the aggregates. In contrast, the TIIGSVS series showed long-range order, and aggregates that were too large and prevented charge transport.
关键词： side-chain engineering,thienoisoindigo,polymer field-effect transistor,Polymeric semiconductors
更新于2025-09-23 15:21:21