Effect of atomic layer deposition temperature on the performance of top-down ZnO nanowire transistors

This paper studies the effect of atomic layer deposition (ALD) temperature on the performance of top-down ZnO nanowire transistors. Electrical characteristics are presented for 10-μm ZnO nanowire field-effect transistors (FETs) and for deposition temperatures in the range 120°C to 210°C. Well-behaved transistor output characteristics are obtained for all deposition temperatures. It is shown that the maximum field-effect mobility occurs for an ALD temperature of 190°C. This maximum field-effect mobility corresponds with a maximum Hall effect bulk mobility and with a ZnO film that is stoichiometric. The optimized transistors have a field-effect mobility of 10 cm²/V.s, which is approximately ten times higher than can typically be achieved in thin-film amorphous silicon transistors. Furthermore, simulations indicate that the drain current and field-effect mobility extraction are limited by the contact resistance. When the effects of contact resistance are de-embedded, a field-effect mobility of 129 cm²/V.s is obtained. This excellent result demonstrates the promise of top-down ZnO nanowire technology for a wide variety of applications such as high-performance thin-film electronics, flexible electronics, and biosensing.     

Thin-film composite crosslinked polythiosemicarbazide membranes for organic solvent nanofiltration (OSN)

In this work we report a new class of solvent stable thin-film composite (TFC) membrane fabricated on crosslinked polythiosemicarbazide (PTSC) as substrate that exhibits superior stability compared with other solvent stable polymeric membranes reported up to now. Integrally skinned asymmetric PTSC membranes were prepared by the phase inversion process and crosslinked with an aromatic bifunctional crosslinker to improve the solvent stability. TFC membranes were obtained via interfacial polymerization using trimesoyl chloride (TMC) and diaminopiperazine (DAP) monomers. The membranes were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and contact angle measurement.The membranes exhibited high fluxes toward solvents like tetrahydrofuran (THF), dimethylformamide (DMF) and dimethylsulfoxide (DMSO) ranging around 20 L/m² h at 5 bar with a molecular weight cut off (MWCO) of around 1000 g/mol. The PTSC-based thin-film composite membranes are very stable toward polar aprotic solvents and they have potential applications in the petrochemical and pharmaceutical industry.     

Preparation and effects of post-annealing temperature on the electrical characteristics of Li–N co-doped ZnSnO thin film transistors

In this study, transparent Li–N co-doped ZnSnO (ZTO: (Li, N)) thin film transistors (TFTs) with a staggered bottom-gate structure were fabricated by radio frequency magnetron sputtering at room temperature. Emphasis was placed on investigating the effects of post-annealing temperature on their physical and electrical properties. An appropriate post-annealing temperature contributes not only to achieving good quality thin films, but also to improving the electrical performance of the ZTO: (Li, N) TFTs. The ZTO: (Li, N) TFTs annealed at 675 °C showed the best electrical characteristics with a high saturation mobility of 26.8 cm²V⁻¹s⁻¹, a threshold voltage of 6.0 V and a large on/off current ratio of 4.5×10⁷.     

Self-limited growth of large-area monolayer graphene films by low pressure chemical vapor deposition for graphene-based field effect transistors

During the last decade, fabrication of high-quality graphene films by chemical vapor deposition (CVD) for nanoelectronics and optoelectronic applications has attracted increasing attention. However, processing of large-area monolayer and defect-free graphene films is still challenging. In this work, we have studied the effect of processing conditions on the self-limited growth of graphene monolayers on copper foils during low pressure CVD both experimentally and theoretically based on thermokinetics and kinetics of Langmuir adsorption. The effect of copper pre-treatment, growth time, and carbon potential of the atmosphere (indicated by the methane-to-hydrogen gas ratio, r) on the quality of graphene nanosheets (number of layers, surface roughness and the lateral size) were studied. Microscopic studies show that careful pre-treatment of the copper foil by electropolishing provides a suitable condition for the self-limited growth of graphene with minimum surface roughness and defects. Raman spectroscopy and atomic force microscopy determine that the number of graphene sheets decreases with increasing the carbon potential while smother surfaces are attained. Large-area monolayer graphene films are obtained at relatively high carbon potential (r=1) and controlled growth time (10 min) at 1000 °C. Measurement of the electrical response of the prepared monolayer graphene films on SiO₂ (300 nm)/Si substrates in a field effect transistor (FET) device shows a high mobility of 2780 cm² V⁻¹ s⁻¹. Interestingly, the device exhibits p-type semiconducting behavior with the Dirac point at a gate voltage of 25 V. The finding show a great promise for graphene-based FET devices for future nanoelectronics.     

Solution-processed ytterbium oxide dielectrics for low-voltage thin-film transistors and inverters

High permittivity (high k) metal-oxide thin films fabricated via solution processes have recently received much attention for the construction of low-operating voltage and high-performance thin-film transistors (TFTs). In this report, amorphous ytterbium oxide (Yb₂O₃) thin films were fabricated by spin coating and their applications in TFTs were explored. The physical properties of the solution-processed Yb₂O₃ thin films processed at different annealing temperatures were systematically investigated using various characterization techniques. To explore the feasibility of the Yb₂O₃ thin films as gate dielectrics for oxide TFTs, In₂O₃ TFTs based on Yb₂O₃ dielectrics were integrated. All the devices could be operated at 3 V, which is critical for the applications in portable, battery-driven, and low-power electronic devices. The optimized In₂O₃/Yb₂O₃ TFT exhibits high electrical performances, including field-effect mobility of 4.98 cm²/V s, on/off current ratio of ~ 10⁶, turn-on voltage around 0 V, and subthreshold swing of 70 mV/decade, respectively. To demonstrate the potential of In₂O₃/Yb₂O₃ TFT toward more complex logic application, the unipolar inverter was further constructed.     

单片机在H^＋—ISFET PH计中的应用

本文是单片机氢离子敏场效应管pH计的研制总结。文中论述了把单片机应用于氢离子敏场效应管pH计中的数学模型和实现方法,以及软件、硬件的组成方式等。     

High-performance ITO/a-IGZO heterostructure TFTs enabled by thickness-dependent carrier concentration and band alignment manipulation

Utilization of highly conductive metal-oxide (MO) film such as indium-tin-oxide (ITO) in a channel layer has been considered as a promising strategy to realize high-mobility thin-film transistors (TFTs). However, achieving high-mobility is typically restricted by severe negative threshold voltage (V_th) shift and large off-current which are consequences of channel thickness increment. Here, to realize high-mobility MO TFTs with low V_th and off-current level, a heterogeneous ITO/amorphous indium-gallium-zinc-oxide (a-IGZO) channel structure was implemented. In the channel, the ultrathin (4 nm) ITO layer contributes to retain high electron concentration and boost the mobility, while the overlayered a-IGZO layer mitigates V_th shift and off-current increase. The ITO/a-IGZO TFTs optimized via the thickness-dependent carrier concentration of ITO and band alignment manipulation in the bilayer considerably improved the device performance showing saturation field-effect mobility of >61 cm²/V·s (average of 58.2 ± 2 cm²/V·s), subthreshold slope of <120 mV/decade (average of 129 ± 12 mV/decade), and current on/off ratio of >5 × 10¹⁰. Various electrical characterization and technological computer-aided design simulation were performed to establish a plausible mechanism explaining enhanced mobility and V_th regulation in the ITO/a-IGZO TFTs. Additionally, systematic stability tests and spectroscopic analysis were carried out to evaluate the operational stability of the device, and it is suggested that Sn ion diffusing from ITO to the heterogeneous interface can be responsible for enhanced stability by reducing the oxygen vacancy defects.     

电子纸技术及其研究现状与展望

就电子纸显示的基本原理和技术特征及其研究进展几个方面做了综合评述 ,并展望了电子纸在未来显示技术和设备中的应用前景。     

Sol-gel processed high-k aluminum oxide dielectric films for fully solution-processed low-voltage thin-film transistors

High-k oxide dielectric films have attracted intense interest for thin-film transistors (TFTs). However, high-quality oxide dielectrics were traditionally prepared by vacuum routes. Here, amorphous high-k alumina (Al₂O₃) thin films were prepared by the simple sol-gel spin-coating and post-annealing process. The microstructure and dielectric properties of Al₂O₃ dielectric films were systematically investigated. All the Al₂O₃ thin films annealed at 300–600?°C are in amorphous state with ultrasmooth surface (RMS ~ 0.2?nm) and high transparency (above 95%) in the visible range. The leakage current of Al₂O₃ films gradually decreases with the increase of annealing temperature. Al₂O₃ thin films annealed at 600?°C showed the low leakage current density down to 3.9?×?10^?7 A/cm² at 3?MV/cm. With the increase of annealing temperature, the capacitance first decreases then increases to 101.1?nF/cm² (at 600?°C). The obtained k values of Al₂O₃ films are up to 8.2. The achieved dielectric properties of Al₂O₃ thin films are highly comparable with that by vapor and solution methods. Moreover, the fully solution-processed InZnO TFTs with Al₂O₃ dielectric layer exhibit high mobility of 7.23?cm² V^?1 s^?1 at the low operating voltage of 3?V, which is much superior to that on SiO₂ dielectrics with mobility of 1.22?cm²/V^?1 s^?1 at the operating voltage of 40?V. These results demonstrate that solution-processed Al₂O₃ thin films are promising for low-power and high-performance oxide devices.     

Optically and electrically excited emissions from organic semiconducting oligomer crystals

This paper reviews optically and electrically excited emissions from organic semiconducting oligomers in the form of their single crystals. Of the semiconducting oligomers, the review focuses on thiophene/phenylene co‐oligomers (TPCOs). The topics cover crystal growth and laser oscillation along with related spectrally narrowed emissions of TPCO crystals. Aside from the strong excitation with a laser beam, weak excitation using a mercury lamp produces optical fringes superimposed on broadband emission spectra. The laser oscillation spectra accompanied by longitudinal multimode and optical fringes observed from the weak excitation have the same origin. This enables us to determine optical constants (i.e. refractive indices) and their dispersion of the crystals and provides sufficient information for the construction of optoelectronic devices based on the organic crystals. As a typical example, the review outlines the improved device constitution and performance as well as device operation methods with light‐emitting field‐effect transistors (LEFETs), because the device configuration is suited for cutting‐edge devices including lasers. Finally the review presents device performance of LEFETs having a diffraction grating. These devices are suited for exploring the possibility of constructing a next‐generation current‐injected laser device. © 2016 The Authors. Polymer International published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.