Junctionless nanowire transistor fabricated with high mobility Ge channel

The junctionless nanowire metal–oxide–semiconductor field‐effect transistor (JNT) has recently been proposed as an alternative device for sub‐20‐nm nodes. The JNT architecture eliminates the need for forming PN junctions, resulting in simple processing and competitive electrical characteristics. In order to further boost the drive current, alternative channel materials such as III–V and Ge, have been proposed. In this Letter, JNTs with Ge channels have been fabricated by a CMOS‐compatible top–down process. The transistors exhibit the lowest subthreshold slope to date for JNT with Ge channels. The devices with a gate length of 3 μm exhibit a subthreshold slope (SS) of 216 mV/dec with an I_ON/I_OFF current ratio of 1.2 × 10³ at V_D = –1 V and drain‐induced‐barrier lowering (DIBL) of 87 mV. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

High‐performance In–Zn–O thin‐film transistors with a soluble processed ZrO2 gate insulator

Spin‐coated zirconium oxide films were used as a gate dielectric for low‐voltage, high performance indium zinc oxide (IZO) thin‐film transistors (TFTs). The ZrO₂ films annealed at 400 °C showed a low gate leakage current density of 2 × 10^–8 A/cm² at an electric field of 2 MV/cm. This was attributed to the low impurity content and high crystalline quality. Therefore, the IZO TFTs with a soluble ZrO₂ gate insulator exhibited a high field effect mobility of 23.4 cm²/V s, excellent subthreshold gate swing of 70 mV/decade and a reasonable I_on/off ratio of ～10⁶. These TFTs operated at low voltages (～3.0 V) and showed high drain current drive capability, enabling oxide TFTs with a soluble processed high‐k dielectric for use in backplane electronics for low‐power mobile display applications. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Effect of antimony doping on the low‐temperature performance of solution‐processed indium oxide thin film transistors

The effects of antimony (Sb) doping on solution‐processed indium oxide (InO_x) thin film transistors (TFTs) were examined. The Sb‐doped InSbO TFT exhibited a high mobility, low gate swing, threshold voltage, and high I_ON/OFF ratio of 4.6 cm²/V s, 0.29 V/decade, 1.9 V, and 3 × 10⁷, respectively. The gate bias and photobias stability of the InSbO TFTs were also improved by Sb doping compared to those of InO_x TFTs. This improvement was attributed to the reduction of oxygen‐related defects and/or the existence of the lone‐pair s‐electron of Sb³⁺ in amorphous InSbO films. (© 2014 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Self‐assembly of poly(3‐hexylthiophene) nanowire networks by a mixed‐solvent approach for organic field‐effect transistors

Organic field‐effect transistors (OFETs) based on interconnected nanowire networks of P3HT have been successfully fabricated by using a mixed‐solvent method. The nanowire network density can be tuned by controlling the anisole/chlorobenzene ratio of mixed solvents. The obtained field‐effect mobility, threshold voltage and the ratio of on‐state current and off‐state current (I_on/I_off) was 0.0435 cm²/V s, –10 V and 1.75 × 10⁴, respectively. The three‐dimensional and interconnected nanowire structure of the networks can enhance the charge transport in P3HT.

     

Effect of temperature–bias annealing on the hysteresis and subthreshold behavior of multilayer MoS2 transistors

The transfer characteristics (I_D–V_G) of multilayers MoS₂ transistors with a SiO₂/Si backgate and Ni source/drain contacts have been measured on as‐prepared devices and after annealing at different temperatures (T_ann from 150 °C to 200 °C) under a positive bias ramp (V_G from 0 V to +20 V). Larger T_ann resulted in a reduced hysteresis of the I_D–V_G curves (from ～11 V in the as‐prepared sample to ～2.5 V after T_ann at 200 °C). The field effect mobility (～30 cm² V^–1 s^–1) remained almost unchanged after the annealing. On the contrary, the subthreshold characteristics changed from the common n‐type behaviour in the as‐prepared device to the appearance of a low current hole inversion branch after annealing. This latter effect indicates a modification of the Ni/MoS₂ contact that can be explained by the formation of a low density of regions with reduced Schottky barrier height (SBH) for holes embedded in a background with low SBH for electrons. Furthermore, a temperature dependent analysis of the subthreshold characteristics revealed a reduction of the interface traps density from ～9 × 10¹¹ eV^–1cm^–2in the as‐prepared device to ～2 × 10¹¹ eV^–1cm^–2after the 200 °C temperature–bias annealing, which is consistent with the observed hysteresis reduction.

Schematic representation of a back‐gated multilayer MoS₂ field effect transistor (left) and transfer characteristics (right) measured at 25 °C on an as‐prepared device and after the temperature–bias annealing at 200 °C under a positive gate bias ramp from 0 V to +20 V.     

The fabrication and characterization of 4H SiC power UMOSFETs

The fabrication of 4H-SiC vertical trench-gate metal-oxide-semiconductor field-effect transistors(UMOSFETs) is reported in this paper.The device has a 15-μm thick drift layer with 3×1015 cm-3 N-type doping concentration and a 3.1μm channel length.The measured on-state source-drain current density is 65.4 A/cm2 at Vg = 40 V and VDS = 15 V.The measured threshold voltage(Vth) is 5.5 V by linear extrapolation from the transfer characteristics.A specific on-resistance(Rsp-on) is 181 mΩ·cm2 at Vg = 40 V and a blocking voltage(BV) is 880 V(IDS = 100 μA@880V) at Vg = 0 V.     

A GaAs MISFET with Ge3N4 gate dielectric

GaAs MIS field effect transistors with a Ge₃N₄ dielectric gate have been investigated. No hysteresis loop and drain current drift has been observed in theI _D -V _Dcharacteristics. However, performance of the devices have been found to be limited by the contact resistance. FromI _DS ^1/2 -V _G plot, the threshold voltage and effective channel mobility of the transistor have been obtained as -4.5V and 2800cm²v^–1s^–1, respectively. A maximum dc transconductance of 68 mS/mm of gate width has been achieved.     

The effects of high-energy ion irradiations on the I–V characteristics of silicon NPN transistors

The silicon NPN rf power transistors were irradiated with different linear energy transfer (LET) ions such as 50?MeV Li³⁺, 80?MeV C⁶⁺ and 150?MeV Ag¹²⁺ ions in the dose range of 1–100?Mrad. The SRIM simulation was used to understand the energy loss and range of these ions in the transistor structure. The different electrical parameters such as Gummel characteristics, excess base current (ΔI_B), DC current gain (h_FE), displacement damage factor (K) and output characteristics were systematically studied before and after irradiation. The ion irradiation results were compared with ⁶⁰Co-gamma irradiation result in the same dose range. A considerable increase in base current (I_B) and a decrease in h_FE and I_CSat were observed after irradiation. The degradation in the electrical parameters was comparably very high for Ag¹²⁺ ion-irradiated transistor when compared to other ion-irradiated transistors, whereas the degradation in the electrical parameters for Li³⁺ and C⁶⁺ ion-irradiated transistors was comparable with gamma-irradiated transistor. The isochronal annealing study was conducted on the 100?Mrad irradiated transistors up to 500°C to analyze the recovery in different electrical parameters. The h_FE and other electrical parameters of irradiated transistors were almost recovered after 500°C for 50?MeV Li³⁺, 80?MeV C⁶⁺ ion and ⁶⁰Co-gamma-irradiated transistors, whereas for 150?MeV Ag¹²⁺ ion-irradiated transistor, the recovery in electrical characteristics is not complete.     

Synthesis and characterization of a family of layered trichalcogenides for assisted hydrogen photogeneration

Three layered trisulfides (TiS₃, ZrS₃, HfS₃) have been synthesized by solid–gas reaction between metal and sulfur in a vacuum sealed ampoule at 550 °C during 60 h. The samples used in this work were prepared from a colloidal suspension of powder of each one of the metal trisulfides (MS₃, M = Ti, Zr, Hf) in ethanol and deposited on titanium disks and quartz substrates by ”drop coating” technique. These samples have been characterized by X‐ray diffraction, energy dispersive analysis of X‐ray and scanning electron microscopy. The obtained direct optical band gaps are 1.0 ± 0.1 eV, 2.0 ± 0.1 eV and 2.2 ± 0.1 eV for TiS₃, ZrS₃ and HfS₃, respectively. Photoelectrochemical measurements in 0.5 M Na₂SO₃ have been carried out to characterize the MS₃/electrolyte interface. The flat‐band potentials (V_fb) vs. Ag/AgCl measured by electrochemical impedance spectroscopy (EIS) are –0.84 ± 0.02 V (TiS₃), –0.93 ± 0.02 V (ZrS₃) and –0.92 ± 0.02 V (HfS₃). Hydrogen generation was investigated in a photoelectrochemical cell (PEC) with MS₃ as photoanodes under white light illumination of 200 ± 20 mW/cm² at external bias potentials of 0.3 V vs. Ag/AgCl. Hydrogen evolution flows have been quantified by quadrupole mass spectrometry (QMS) reaching instantaneous values up to 19 ± 2 nmol H₂/min cm² with TiS₃ as photoanode.     

有机薄膜晶体管中接触效应的研究

研究了接触效应对有机薄膜晶体管性能的影响.首先在n型重掺杂Si片上制备了以M_OO₃修饰的Al电极为源漏电极的Pentacene基OTFTs(organic thin film transistors),器件场效应迁移率μ_ef达到0.42 cm²/V ·s,阈值电压V_T为-9.16 V,开关比4.7×10³.通过中间探针法,对器件电势分布做了定性判断 关键词： 有机薄膜晶体管 场效应迁移率 接触效应 电荷漂移     

P‐type tin‐oxide thin film transistors for blue‐light detection application

We reported the characteristics of p‐type tin‐oxide (SnO) thin film transistors (TFTs) upon illumination with visible light. Our p‐type TFT device using the SnO film as the active channel layer exhibits high sensitivity toward the blue‐light with a high light/dark read current ratio (I_light/I_dark) of 8.2 × 10³ at a very low driven voltage of <3 V. Since sensing of blue‐light radiation is very critical to our eyes, the proposed p‐type SnO TFTs with high sensitivity toward the blue‐light show great potential for future blue‐light detection applications.

     

Utilization of surface plasmon resonance of Au/Pt nanoparticles for highly photosensitive ZnO nanorods network based plasmon field effect transistor

Hydrothermally processed highly photosensitive ZnO nanorods based plasmon field effect transistors (PFETs) have been demonstrated utilizing the surface plasmon resonance coupling of Au and Pt nanoparticles at Au/Pt and ZnO interface. A significantly enhanced photocurrent was observed due to the plasmonic effect of the metal nanoparticles (NPs). The Pt coated PFETs showed I_on/I_off ratio more than 3 × 10⁴ under the dark condition, with field-effect mobility of 26 cm² V⁻¹ s⁻¹ and threshold voltage of −2.7 V. Moreover, under the illumination of UV light (λ = 350 nm) the PFET revealed photocurrent gain of 10⁵ under off-state (−5 V) of operation. Additionally, the electrical performance of PFETs was investigated in detail on the basis of charge transfer at metal/ZnO interface. The ZnO nanorods growth temperature was preserved at 110 °C which allowed a low temperature, economical and simple method to develop highly photosensitive ZnO nanorods network based PFETs for large scale production.     

低栅极电压控制下带有phenyltrimethoxysilane单分子自组装层的有机薄膜晶体管场效应特性研究

制作了底栅极顶接触有机薄膜晶体管器件,60 nm的pentacene被用作有源层,120 nm热生长的SiO₂作为栅极绝缘层.通过采用不同自组装修饰材料对器件的有源层与栅极绝缘层之间的界面进行修饰,如octadecyltrichlorosilane （OTS）,phenyltrimethoxysilane （PhTMS）,来比较界面修饰层对器件性能的影响.同时对带有PhTMS修饰层的OTFTs器件低栅极电压调制下的场效应行为及其载流子的传输机理进行研究.结果得到,当|V 关键词： 有机薄膜晶体管 自组装单分子层 场效应迁移率 低栅极调制电压     

Highly stable amorphous indium‐zinc‐oxide thin‐film transistors with back‐channel wet‐etch process

The stabilities of amorphous indium‐zinc‐oxide (IZO) thin film transistors (TFTs) with back‐channel‐etch (BCE) structure are investigated. A molybdenum (Mo) source/drain electrode was deposited on an IZO layer and patterned by hydrogen peroxide (H₂O₂)‐based etchants. Then, after etching the Mo layer, SF₆ plasma with direct plasma mode was employed and optimized to improve the bias stress stability. Scanning electron microscopy and X‐ray photoelectron spectroscopic analysis revealed that the etching residues were removed efficiently by the plasma treatment. The modified BCE‐ TFTs showed only threshold voltage shifts of 0.25 V and –0.20 V under positive/negative bias thermal stress (P/NBTS, V_GS = ±30 V, V_DS = 0 V and T = 60 °C) after 12 hours, respectively. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

High performance Zn–Sn–O thin film transistors with Cu source/drain electrode

Zn–Sn–O (ZTO) thin film transistors (TFTs) were fabricated with a Cu source/drain electrode. Although a reasonably high mobility (μ_FE) of 13.2 cm²/Vs was obtained for the ZTO TFTs, the subthreshold gate swing (SS) and threshold voltage (V_th) of 1.1 V/decade and 9.1 V, respectively, were inferior. However, ZTO TFTs with Ta film inserted as a diffusion barrier, exhibited improved SS and V_th values of 0.48 V/decade and 3.0 V, respectively as well as a high μ_FE value of 18.7 cm²/Vs. The improvement in the Ta‐inserted device was attributed to the suppression of Cu lateral diffusion into the ZTO channel region. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Catalysis by hydrogen chloride in the gas‐phase elimination kinetics of 2‐phenyl‐2‐propanol and 3‐methyl‐1‐buten‐3‐ol

A homogeneous, molecular, gas‐phase elimination kinetics of 2‐phenyl‐2‐propanol and 3‐methyl‐1‐ buten‐3‐ol catalyzed by hydrogen chloride in the temperature range 325–386 °C and pressure range 34–149 torr are described. The rate coefficients are given by the following Arrhenius equations: for 2‐phenyl‐2‐propanol log k₁ (s^?1) = (11.01 ± 0.31) ? (109.5 ± 2.8) kJ mol^?1 (2.303 RT)^?1 and for 3‐methyl‐1‐buten‐3‐ol log k₁ (s^?1) = (11.50 ± 0.18) ? (116.5 ± 1.4) kJ mol^?1 (2.303 RT)^?1. Electron delocalization of the CH₂?CH and C₆H₅ appears to be an important effect in the rate enhancement of acid catalyzed tertiary alcohols in the gas phase. A concerted six‐member cyclic transition state type of mechanism appears to be, as described before, a rational interpretation for the dehydration process of these substrates. Copyright © 2007 John Wiley & Sons, Ltd.     

A Possible Nuclear Spin Dewar. Hyperfine Interactions of Short-Lived β Emitter 8Li and 12B in TiO2

It was confirmed by detecting the β-NMR of ¹²B (I ^π=1⁺, T _1/2=20.2 ms) in a TiO₂ (rutile) crystal that the nuclear spin polarization of ¹²B was totally maintained in the crystal as produced through a nuclear reaction before implantation. Two locations, site 1 and site 2, were found with the relative populations 9 and 1, respectively, and the electric field gradients (EFGs) at those sites were obtained to be q(site 1)=+(37.1±0.5)10¹⁵ V/cm², η(site 1)<0.03, q(site 2)=+(185±5)10¹⁵ V/cm² and η(site 2)=0.62±0.02. We also found that about 30% of the initial polarization of ⁸Li (I ^π=2⁺, T _1/2=838 ms) was maintained in the crystal. Since the polarizations of other β emitting nuclei, ^12,16N, ^13,19O, and ⁴¹Sc were also totally maintained in the crystal, the crystal can be a “Spin Dewar” in which many short-lived nuclides can be implanted with their polarizations totally maintained during their lifetimes for the studies not only on the electronic structure of impurities in it but also on the nuclear properties. This revised version was published online in September 2006 with corrections to the Cover Date.     

Improving the mobility of CuPc OFETs by varying the preparation conditions

In this work, three different preparation conditions were used for testing the performance of p-conducting copper phthalocyanine (CuPc) organic field-effect transistors (OFETs). The charge carrier mobility (μ _sat=(1.5±0.6)×10^?3 cm²/V?s) of the CuPc OFETs with the CuPc film deposited while keeping the substrate at room temperature could be improved when the gate dielectric was modified by a self-assembled monolayer of n-octadecyltrichlorosilane (μ _sat=(3.8±0.4)×10^?3 cm²/V?s) or when elevated temperatures were applied to the substrate (T _S,av=127 ^°C) during the deposition of the organic film (μ _sat=(6.5±0.8)×10^?3 cm²/V?s). For the latter case, the dependence of the mobility and threshold voltage with increasing thickness of the organic film was tested—above 13 nm film thickness, no further significant increase of the hole mobility or change in the threshold voltage could be observed. The environmental stability of the OFETs was checked by performing ex situ measurements immediately as the sample was exposed to atmosphere and after 40 days of exposure. The effect of the different preparation conditions on the morphology of the organic films prepared in this work is also discussed in this context.     

Flexible InGaZnO thin film transistors using stacked Y2O3/TiO2/Y2O3 gate dielectrics grown at room temperature

In this Letter, we report a low operation voltage and high mobility flexible InGaZnO thin‐film transistor (TFT) using room‐temperature processed Y₂O₃/TiO₂/Y₂O₃ gate dielectric. The flexible IGZO TFT showed a low threshold voltage of 0.75 V, a small sub‐threshold swing of 137 mV/decade, a good field effect mobility of 32.7 cm²/V s, and a large I_on/I_off ratio of 1.7 × 10⁶. The low operation voltage, small sub‐threshold swing and high mobility could be ascribed to the combination of high‐κ TiO₂ and large band gap Y₂O₃, which provide the potential to meet the requirements of low‐temperature and low‐power portable electronics.

     

Nuclear quadrupole resonance studies of209Bi in Bi4(GeO4)3 and Bi4(SiO4)3

Nuclear quadrupole resonance (NQR) of²⁰⁹Bi has been studied in Bi₄ (GeO₄)₃ and Bi₄ (SiO₄)₃ using a wide band coherence-controlled superregenerative oscillator-detector. All the four allowed (ΔM _I=±1) transitions are observed. In both cases the electric field gradient (EFG) tensor is axially symmetric (η=0.0). The quadrupole coupling constante ² qQ is measured to be 490.8±1 MHz and 470.4±1 MHz respectively. It is pointed out that the purely ionic model is inadequate to understand these results. With the available experimental accuracy and the strength of the applied electric field (∼ 6 KV/cm), no field-induced effects on the NQR spectrum could be observed in the case of Bi₄ (SiO₄)₃.