我们制作和表征双栅石墨烯场效应晶体管（FET）使用氧化铝作为顶栅电介质。我们使用薄Al膜作为成核层，以使Al 2 O3的原子层沉积。我们的器件在室温下显示出超过8,000 cm 2/Vs的迁移率值，这一发现表明顶栅叠层不会显著增加载流子散射，从而降低器件特性。我们提出了一个设备模型，以适应使用一个单一的流动性值的实验数据。
英文摘要：
We fabricate and characterize dual-gated graphene field-effect transistors (FETs) using Al2O3 as top-gate dielectric. We use a thin Al film as a nucleation layer to enable the atomic layer deposition of Al2O3. Our devices show mobility values of over 8,000 cm2/Vs at room temperature, a finding which indicates that the top-gate stack does not significantly increase the carrier scattering, and consequently degrade the device characteristics. We propose a device model to fit the experimental data using a single mobility value.
Using in-situ Raman scattering from phosphorene channel in an electrochemically top-gated field effect transistor, we show that its phonons with A$_g$ symmetry depend much more strongly on concentration of electrons than that of holes, while the phonons with B$_g$ symmetry are insensitive to doping. With first-principles theoretical analysis, we show that the observed electon-hole asymmetry arises from the radically different constitution of its conduction and valence bands involving $π$ and $σ$ bonding states respectively, whose symmetry permits coupling with only the phonons that preserve th…
Top-gated graphene field-effect-transistors formed by decomposition of SiC
在热分解的半绝缘4 H-SiC衬底上制作了顶栅少层石墨烯场效应晶体管。物理气相沉积的SiO2被用作栅极电介质。通过高分辨率扫描隧道显微镜观察到的具有正确晶格矢量的碳原子的二维六边形排列证实了在SiC衬底顶部形成多个石墨烯层。n型和p型跃迁的观察进一步证实了狄拉克费米子在石墨烯层中独特的输运性质。在这些制造的石墨烯FET上测得的电子和空穴迁移率分别高达5400 cm 2/Vs和4400 cm 2/Vs，这比常规SiC或硅的相应值大得多。
We demonstrate non-volatile, n-type, back-gated, MoS$_{2}$ transistors, placed directly on an epitaxial grown, single crystalline, PbZr$_{0.2}$Ti$_{0.8}$O$_{3}$ (PZT) ferroelectric. The transistors show decent ON current (19 $μA/μ$m), high on-off ratio (10$^{7}$), and a subthreshold swing of (SS ~ 92 mV/dec) with a 100 nm thick PZT layer as the back gate oxide. Importantly, the ferroelectric polarization can directly control the channel charge, showing a clear anti-clockwise hysteresis. We have selfconsistently confirmed the switching of the ferroelectric and corresponding change in channel cu…
High Mobility Ambipolar MoS2 Field-Effect Transistors: Substrate and Dielectric Effects
我们在二氧化硅和聚甲基丙烯酸甲酯（PMMA）衬底上制作了二硫化钼场效应晶体管，并在四探针配置中测量了载流子迁移率。对于SiO2上的多层MoS 2，迁移率为30-60 cm 2/Vs，与厚度（15-90 nm）相对无关，并且大多数器件表现出单极n型行为。相比之下，PMMA上的多层MoS 2显示出随厚度增加的迁移率，在厚度约50 nm处高达470 cm 2/Vs（电子）和480 cm 2/Vs（空穴）。迁移率对厚度的依赖性指向在增加迁移率中的块状MoS 2的长程介电效应。
Statistical Study of Deep Sub-Micron Dual-Gated Field-Effect Transistors on Monolayer CVD Molybdenum Disulfide Films
具有1.8 eV直接带隙的单层二硫化钼（MoS 2）是一种有前途的二维材料，在下一代纳米电子应用中有可能超过石墨烯。本文采用化学气相沉积（CVD）方法在Si/SiO_2衬底上制备单层MoS_2薄膜，并对基于双栅MoS_2场效应晶体管的器件性能进行了全面的研究。超过100个设备进行了研究，以获得在CVD二硫化钼的设备性能的统计描述。我们检查和缩小规模的晶体管的沟道长度为100 nm，并实现了创纪录的高漏电流62.5 mA/mm的CVD单层二硫化钼膜以往报道。我们进一步提取了低功函数金属Ti在单层CVD MoS 2上的本征接触电阻，其期望值为175 Ω.mm，通过适当的选通可以显著降低到10 Ω.mm。最后，得到了不同沟道长度下载流子的场效应迁移率（μFE）。考虑到接触电阻的影响，单层CVD MoS 2薄膜的平均和最大本征μFE分别为13.0和21.6 cm 2/Vs。
The Effect of Dielectric Capping on Few-Layer Phosphorene Transistors: Tuning the Schottky Barrier Heights
磷烯是一种独特的具有二维层状结构的单元素半导体。在这封信中，我们研究了机械剥离的少层磷烯顶栅晶体管的行为。我们实现了144 mA/mm的高导通电流和95.6 cm 2/Vs的空穴迁移率。我们沉积Al 2 O3原子层沉积（ALD）和研究的电介质覆盖的影响。我们观察到，晶体管的极性交替从p型到双极与Al 2 O 3生长在顶部。我们将这种转变归因于金属接触边缘处的电子和空穴的有效肖特基势垒高度的变化，这源于ALD电介质中的固定电荷。
Double Gated Single Molecular Transistor for Charge Detection
采用基于密度泛函理论的第一性原理计算和非平衡格林函数方法研究了1，3-环丁二烯（C $_{4}$ H $_{4}$）单分子晶体管（SMT）的静电行为.当分子被放置在电介质层（由金属栅极支撑）的顶部上并且在源极/漏极电极之间弱耦合时，电荷稳定性图揭示了在库仑阻塞机制中存在单独的电荷状态。这在添加另一个置于分子顶部的栅电极时受到显著影响。这种改进的双门控几何结构允许对系统的总能量进行额外的控制，该系统对分子的各个电荷状态敏感，这可以用作在室温下操作的电荷感测技术。
Gate-all-around nanowire transistor, due to its extremely tight electrostatic control and vertical integration capability, is a highly promising candidate for sub-5 nm technology node. In particular, the junctionless nanowire transistors are highly scalable with reduced variability due to avoidance of steep source/drain junction formation by ion implantation. Here we demonstrate a dual-gated junctionless nanowire \emph{p}-type field effect transistor using tellurium nanowire as the channel. The dangling-bond-free surface due to the unique helical crystal structure of the nanowire, coupled with…
Graphene field-effect transistors are widely used for development of biosensors. However, certain fundamental questions about details of their functioning are not fully understood yet. One of these questions is the presence of gate (leakage) currents in the electrolyte-gated configuration. Here, we report our observations considering causes of this phenomena on chemical vapor deposition (CVD) grown graphene. We observed that gate currents reflect currents that occur on the transistor surface similarly to a working electrode - counter electrode pair currents in an electrochemical cell. Gate cur…
The energy bandgap is an intrinsic character of semiconductors, which largely determines their properties. The ability to continuously and reversibly tune the bandgap of a single device during real time operation is of great importance not only to device physics but also to technological applications. Here we demonstrate a widely tunable bandgap of few-layer black phosphorus (BP) by the application of vertical electric field in dual-gated BP field-effect transistors. A total bandgap reduction of 124 meV is observed when the electrical displacement field is increased from 0.10V/nm to 0.83V/nm. …
Diamond has attracted attention as a next-generation semiconductor because of its various exceptional properties such as a wide bandgap and high breakdown electric field. Diamond field effect transistors, for example, have been extensively investigated for high-power and high-frequency electronic applications. The quality of their charge transport (i.e., mobility), however, has been limited due to charged impurities near the diamond surface. Here, we fabricate diamond field effect transistors by using a monocrystalline hexagonal boron nitride as a gate dielectric. The resulting high mobility o…
We study the effect of polymer coating, pressure and temperature on the electrical characteristics of monolayer WSe2 back-gated transistors with quasi-ohmic Ni/Au contacts. We find that the removal of a layer of poly(methyl methacrylate) or decreasing the pressure change the device conductivity from p to n-type. We study the current-voltage characteristics as a function of the temperature and measure a gate-tunable Schottky barrier at the contacts with a height of 60 meV in flat-band condition. We report and discuss a change in the mobility and the subthreshold slope observed with increasing t…
Solution processed field-effect transistors based on single crystalline silicon nanowires (Si NWs) with metal Schottky contacts are demonstrated. The semiconducting layer was deposited from a nanowire ink formulation at room temperature. The devices with 230nm thick SiO2 gate insulating layers show excellent output current-voltage characteristics with early saturation voltages under 2 volts, constant saturation current and exceptionally low dependence of saturation voltage with the gate field. Operational principles of these devices are markedly different from traditional ohmic-contact field-e…
In-situ Raman Spectroscopy of the Graphene / Water Interface of a Solution-Gated Field Effect Transistor: Electron-Phonon Coupling and Spectroelectrochemistry
We study the electrical transport in back-gate field-effect transistors with ultrathin palladium diselenide (PdSe2) channel. The devices are normally-on and exhibit dominant n-type conduction at low pressure. The electron conduction, combined with the sharp edge and the workfunction decreasing with the number of layers, opens the way to applications of PdSe2 nanosheets in vacuum electronics. In this work, we demonstrate field emission from few-layer PdSe2 nanosheets with current up to the uA and turn-on field below 100 V/um, thus extending the plethora of applications of this recently isolated…
We demonstrate an electrolyte-gated hybrid nanoparticle/organic synapstor (synapse-transistor, termed EGOS) that exhibits short-term plasticity as biological synapses. The response of EGOS makes it suitable to be interfaced with neurons: short-term plasticity is observed at spike voltage as low as 50 mV (in a par with the amplitude of action potential in neurons) and with a typical response time in the range of tens milliseconds. Human neuroblastoma stem cells are adhered and differentiated into neurons on top of EGOS. We observe that the presence of the cells does not alter short-term plastic…
In this article, a novel two-path model is proposed to quantitatively explain sub-threshold characteristics of back-gated Schottky barrier FETs (SB-FETs) from 2D channel materials. The model integrates the 'conventional' model for SB-FETs with the phenomenon of contact gating - an effect that significantly affects the carrier injection from the source electrode in back-gated field effect transistors. The two-path model is validated by a careful comparison with experimental characteristics obtained from a large number of back-gated WSe2 devices with various channel thicknesses. Our findings are…
A general self-aligned fabrication scheme is reported here for a diverse class of electronic devices based on van der Waals materials and heterojunctions. In particular, self-alignment enables the fabrication of source-gated transistors in monolayer MoS2 with near-ideal current saturation characteristics and channel lengths down to 135 nm. Furthermore, self-alignment of van der Waals p-n heterojunction diodes achieves complete electrostatic control of both the p-type and n-type constituent semiconductors in a dual-gated geometry, resulting in gate-tunable mean and variance of anti-ambipolar Ga…
Organic semiconductors are usually not thought to show outstanding performance in highly-integrated, sub 100 nm transistors. Consequently, single-crystalline materials such as SWCNTs, MoS2 or inorganic semiconductors are the material of choice at these nanoscopic dimensions. Here, we show that using a novel vertical field-effect transistor design with a channel length of only 40 nm and a footprint of 2 x 80 x 80 nm$^2$, high electrical performance with organic polymers can be realized when using electrolyte gating. Our organic transistors combine high on-state current densities of above 3 MA/c…
Multi-Branch Transport in a Back-gated WS$_2$ Transistor at Deep-Cryogenic Temperature
University of Strathclyde（斯特拉斯克莱德大学）；Tyndall National Institute, University College Cork（科克大学廷德尔国家研究所）；School of Chemistry, University College Cork（科克大学化学学院）；National Physical Laboratory（英国国家物理实验室）
The realization of both p-type and n-type operations in a single organic field effect transistor (OFET) is critical for simplifying the design of complex organic circuits. Typically, only p-type or n-type operation is realized in an OFET, while the respective counterpart is either suppressed by charge trapping or limited by the injection barrier with the electrodes. Here we show that only the presence of a top dielectric turns an n-type polymer semiconductor (N2200, Polyera ActiveInk) into an ambipolar one, as detected from both bottom and top gated OFET operation. The effect is independent of…
