基于全印刷技术的四针状氧化锌表面传导场发射器件

利用全丝网印刷技术制备四针状氧化锌表面传导场发射器件,并测试其场发射性能。SEM表明所合成的四针状氧化锌均匀地沉积在阴栅间隙,形成传导层。场发射测试结果表明,随着阳极电压增高,阳极电流增大,开启电压降低。当阳极电压为2 400 V时,器件的开启电压降为70 V;栅压为120 V时,器件最高亮度达550 cd/m2。对器件进行450 min的电流稳定性跟踪测量,其阳极电流波动在4%以内,表明该器件具有良好的场发射稳定性。     

氧化锌纳米阵列场发射性能研究

采用物理气相沉积的方法通过控制生长参数，在硅衬底上获得不同形貌的氧化锌纳米阵列。在金属场发射系统中测量了它们的场致电子发射性能，发现阴极发射电流不稳定主要是由于氧化锌纳米阵列的不均匀性造成的．采用高压励炼技术可以增强氧化锌场发射的稳定性，使电流波动明显降低．此外，形貌对氧化锌纳米阵列的场发射电流密度和阈值电压有明显影响，而且不同形貌的氧化锌纳米阵列的抗溅射能力也不相同．     

氧化锌低维结构材料场发射性能研究进展

ZnO具有负的电子亲和势、丰富的结构和形貌可设计性以及良好的机械和化学稳定性等优点,是一种最有前途的阴极电子发射材料.结合作者实验室的工作,综述了近年来迅速发展的ZnO低维结构的场发射特性以及制备方法、形貌结构、排列及密度、表面吸附、掺杂和热处理等因素对其场发射性能的影响,介绍了四针状氧化锌晶须(T-ZnOw)作为场发射阴极材料的优势.     

强发射电流铁电阴极真空二极管试验装置的研制

铁电阴极材料,作为一种新型功能材料,因其发射电流密度高且对使用环境无苛刻要求,而得到各国高度重视.为了测试其电流发射密度,作者研制了铁电阴极真空二极管试验装置,并加以改进,然后将锆钛酸铅(PZT)铁电材料封装入二极管中,进行电子发射试验研究.结果表明,所研制的真空二极管,其真空度达到了试验要求,屏蔽了地电流信号对样品信号的干扰,达到了强电流铁电阴极材料发射电流密度测试的基本要求,为铁电阴极材料在真空二极管中的实用化奠定了基础.     

场致发射体的局域功函数研究

实际场致发射体表面不可能绝对光滑 ,而具有原子尺度的微小凸起会导致发射电流大大增加。基于发射电流主要来自于原子尺度微小凸起的假设 ,提出了局域半球镜像电荷模型 ,研究了场致发射功函数的降低 ,发现微小凸起处场致发射的局域功函数会降低而场增强因子将增大。将它代入F N公式计算了一个典型的单尖Spindt阴极的发射电流 ,所得结果与实验符合。在只考虑Nottingham效应的情况下 ,计算了一些材料Spindt型阴极每微尖的最大稳定发射电流     

碳纳米管冷阴极大电流发射机理的研究

本文对碳纳米管冷阴极的场致发射机理进行了理论和实验研究.研究发现,如果场致发射冷阴极的发射面积很小,有可能得到较大的发射电流密度.当发射面积增加时,冷阴极的平均发射电流密度迅速下降,很难得到大的束电流.研究表明,在碳纳米管冷阴极的场致发射现象中,边沿场的场致发射现象起着非常重要作用.如果仅仅增加发射面积,边沿发射电流增加不多,这导致了平均发射电流密度的下降.因此,在阴极结构中增加发射体的边沿,则可有效提高阴极的发射电流.     

镍硅颗粒膜的表面传导电子发射特性

本文提出采用镍硅颗粒薄膜作为表面传导电子发射显示的发射体材料,通过光刻和磁控溅射在两电极(10μm间隙)之间制备30 nm厚的镍硅颗粒膜。施加三角波电压进行电形成工艺,并测试了器件的电学特性。获得主要结果有,在器件阳极电压2000 V和器件阴极电压13 V的作用下,可以重复探测到稳定的器件发射电流,并且随器件阴极电压的增加而明显增加,最大的发射电流达到了1.84μA(共18个单元);电形成过程中,单个发射体单元的薄膜电阻从13Ω增加到10913Ω;通过对器件发射电流的Fowler-Nordheim结分析,可以确定电子发射机理属于场致电子发射。     

用于平面显示的MISM结构阴极

讨论了平面型场致热化电子发射阴极,对玻璃衬底/Mo/Ta2O5/ZnS/Au结构的平面型场致热化电子发射阴极的制备及其发射性能进行了论述,讨论了在不同工艺参数下器件的发射情况。实验表明,通过优化溅射时间参数和工艺手段制成的阴极对发射电流的大小有很大影响。通过对这些工艺参数的调整,得到了最高发射比(Ia/Ig)为4.5×10-4,向该阴极实用化迈进了一步。     

缺位型强电流铁电阴极材料的研究

采用一种新型的缺位型铁电陶瓷作为阴极材料 ,获得了 1 87A/cm2 的强电流发射密度。通过缺位型与非缺位型材料的发射电流的对比 ,从理论上分析了缺位对于电子发射的影响 ,从材料学角度出发 ,总结出提高发射电流密度的三种有效方法 :即增强阴极表面半导体性 ,增大内偏置电场和增大材料的介电常数     

后栅型场发射显示器窜压现象的研究

提出后栅型场发射显示器(FED)测试过程中的窜压现象,解释该现象的产生原因。阴极电极侧壁场发射电子轰击栅极导致电压表示数发生变化。针对此问题设计一种具有沟槽状介质层结构的后栅型FED从而避免阴极电极侧壁的电子发射。采用全印刷技术制作场发射显示阵列。实验表明此器件具有良好的发射稳定性及栅压调控特性,有效杜绝窜压现象的发生。阳极电压为600 V,栅极电压在100~250 V范围内对阳极电流有良好的调控作用。     

Field emission characteristics from tapered ZnO nanostructures grown onto vertically aligned carbon nanotubes

Zinc oxide (ZnO) nanostructures were grown on vertically aligned carbon nanotubes (CNTs) using thermal chemical vapor deposition (CVD) to enhance the field emission characteristics. The shape of ZnO nanostructure was tapered. Scanning electron microscopy (SEM) image showed the ZnO nanostructures were grown onto CNT surface uniformly. The field electron emission of pristine CNTs and ZnO-coated CNTs were measured. The results showed that ZnO nanostructures grown onto CNTs could improve the field emission characteristics. The ZnO-coated CNTs had a threshold electric field at about 3.1 V/μm at 1.0 mA/cm². The results demonstrated that the ZnO-coated CNT is an ideal field emitter candidate material. The stability of the field emission current was also tested.     

Optical and field emission properties of Zinc Oxide nanostructures

Zinc Oxide (ZnO) nano-pikes were produced by oxidative evaporation and condensation of Zn powders. The crystalline structure and optical properties of the ZnO nanostructures (ZnONs) greatly depend on the deposition position of the ZnONs. TEM and XRD indicated that the ZnONs close to the reactor center, ZnON-A, has better crystalline structure than the ZnONs away from the center, ZnON-B. ZnON-A showed the PL and Raman spectra characteristic of perfect ZnO crystals, whereas ZnON-B produced very strong green emission band at 500 nm in the photoluminescence (PL) spectrum and very strong Raman scattering peak at 560 cm(-1), both related to the oxygen deficiency due to insufficient oxidation of zinc vapor. ZnON-B exhibited better field emission properties with higher emission current density and lower turn-on field than ZnON-A.     

Morphology and properties of ZnO nanostructures by electrochemical deposition: effect of the substrate treatment

Zinc Oxide (ZnO) nanostructures have been grown by electrochemical deposition on the indium-tin oxide (ITO) substrates. The influences and mechanism of pre-treatment of ITO on the morphology, density and size of ZnO nanostructures have been studied. Hexagonal dumbbell-like shape of ZnO bipods have been obtained because of the absence of nucleation sites on the unetched ITO substrate. An ITO etching process in dilute HCl results in the instantaneous and high density nucleation process, which was introduced to reduce the system energy and increase the growth density of ZnO nanostructures. Therefore, well-defined hexagonal and dense ZnO nanorods array are deposited on the etched ITO surface.     

Growth of zinc oxide nanorods, tetrapods, and nanobelts without catalyst

Zinc oxide (ZnO) nanostructures with various morphologies have been synthesized without catalyst in a one-step simple redox process. The results show that ZnO nanorods, nanobelts, and tetrapods with hexagonal needled arms could be synthesized via thermal treatment of a mixture of zinc oxide and charcoal powder in a muffle furnace at 1000-1200 degrees C for 240 min. XRD analyses showed that polycrystalline ZnO phase with wurtzite crystal structure was formed. At a relatively low temperature, 1000 degrees C, the ZnO structure was found to be a bundle of denser nanorods. By increasing the reaction temperature to 1100 degrees C, tetrapod-like structures of needle-like arms with pyramidal tips were formed. With the increase of temperature up to 1200 degrees C, the morphology of ZnO nanostructures changed from nanorods and tetrapods to coalescence grains. Reaction temperature was found to be the most important experimental parameter that played an important role in controlling the mode, mechanism of growth, and formation of different ZnO morphologies.     

Fabrication and characterization of tetrapod-like ZnO nanostructures prepared by catalyst-free thermal evaporation

Tetrapod-like ZnO nanostructures were fabricated on ZnO-coated sapphire (001) substrates by two steps: pulsed laser deposition (PLD) and catalyst-free thermal evaporation process. First, the ZnO films were pre-deposited on sapphire (001) substrates by PLD. Then the ZnO nanostructures grew on ZnO-coated sapphire (001) substrate by the simple thermal evaporation of the metallic zinc powder at 900 °C in the air without any catalysts. The pre-deposited ZnO films by PLD on the substrates can provide growing sites for the ZnO nanostructures. The as-synthesized ZnO nanostructures were characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and Fourier transform infrared spectrum (FTIR). The results show that the tetrapod-like ZnO nanostructures are highly crystalline with the wurtzite hexagonal structure. Photoluminescence (PL) spectrum of as-synthesized nanostructures exhibits a UV emission peak at ～ 389 nm and a broad green emission peak at ～ 513 nm. In addition, the growth mechanism of ZnO nanostructures is also briefly discussed.     

Synthesis of Mn doped ZnO nanocrystals by solvothermal route and its characterization

Undoped and Manganese doped Zinc Oxide were prepared by solvothermal technique. The structural analysis was carried out using X-ray diffraction. It showed that the undoped Zinc Oxide and Manganese doped Zinc Oxide nanocrystals to exhibit hexagonal wurtzite structure. Grain sizes were estimated from Atomic Force Microscopy and Transmission Electron Microscopy images. The surface morphological studies from Scanning Electron Microscope, Transmission Electron Microscope and Atomic Force Microscope depicted spherical particles with formation of clusters. The magnetic behavior studied by Vibrating Sample Magnetometer indicated paramagnetic behaviour. Hyperfine splitting is observed using Electron Spin Resonance studies.     

Development of ZTO/Ag/ZTO transparent electrodes for thin film solar cells

Journal of Materials Science: Materials in Electronics - This article presents the optimization of Zinc Tin Oxide/Silver/Zinc Tin Oxide (ZTO/Ag/ZTO) multilayers to implement them in thin film solar...     

Application of field emission as backlight unit for liquid crystal displays

The paper first analyzes the effect of backlight unit for liquid crystal displays on the respect of image quality and power consumption. A spatially and temporally addressable backlight is required in the future liquid crystal displays which have lower power consumption and higher image quality. Compared to the currently used light emitting diode backlight, the simulation results indicate that a rectangular-shaped backlight has better performances on the respect of reducing power consumption and improving image quality. A backlight cell based on the field emission is manufactured and studied. It uses a mixture of multi-wall carbon nanotubes and tetrapod-like zinc oxide nanostructures as the cathode and applies spin-coating process for fabrication. The experiment shows that such field emission backlight unit has a low turn-on field which enables a high backlight luminance at acceptable driving voltage. Besides, this mixture cathode helps to improve the uniformity of field emission in both spatial and temporal domain which is important for the application of backlight unit.     

Influence of Mg doping on the microstructure and PL emission of wurtzite ZnO synthesized by microwave processing

In this paper, we report the synthesis of nano-structured Zinc Oxide (ZnO) and Magnesium doped Zinc Oxide (ZnO:Mg) using air stable and inexpensive chemicals, by microwave assisted processing. The as-synthesized ZnO and ZnO:Mg nanopowders were annealed at 800 °C for 1 h. The samples were further characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy (SEM) and room temperature photoluminescence (PL) spectra. The crystallite size of ZnO decreased from 24 to 16 nm, and the intensity of most prominent vibration band of ZnO becomes weak when Mg dopant is added. SEM images of Mg doped ZnO showed clearly distinct hexagonal shaped nanoparticles with good crystalline quality and size contrast to ZnO. The PL result indicate that the ZnO exhibit strong and sharp UV emission peak at 380 nm. Our result showed that, by doping magnesium into ZnO, the UV emission peak shift towards the lower wavelength at ~370 nm with increasing intensity, which may be attributed to the size confinement. From this study, the microwave processing method has been proved to be successful for preparing other metal oxide nanopowders with good crystal quality.     

Structural and optical characterization of hydroxy-propyl methyl cellulose-capped ZnO nanorods

Zinc oxide nanostructures have been synthesized using an eco-friendly bottom-up synthesis technique. Effect of hydroxy-propyl methyl cellulose-capping concentration is observed for the effectiveness in limiting the particle growth. It is observed that the structural and optical characteristics have strong dependence on capping concentration. Detailed structural characterizations confirmed that the as-prepared products possess a wurtzite hexagonal phase and the preferred direction of growth is along the c-direction. UV–Visible absorption investigation reveal variation in optical band gap. Room temperature energy resolved photoluminescence spectra of the obtained nanostructures show band edge emission as well as blue-green emission.