SiO_2对ZnO压敏电阻器性能的影响

实验研究了ＳｉＯ２对ＺｎＯ压敏电阻器性能的影响，在ＺｎＯ陶瓷中，添加适量的ＳｉＯ２可以提高压敏电阻器的α值和电压梯度，降低漏泄电流，提高通流量，能够制造出性能优异的ＺｎＯ压敏电阻器。     

液相法制备ZnO压敏电阻器粉料

用液相法制得ＺｎＯ压敏电阻器粉料。与用传统粉料制备的ＺｎＯ压敏电阻器相比,用该粉料制成的ＺｎＯ压敏电阻器的一致性更好、耐电流冲击能力更强、压敏场强更高。     

ZnO压敏电阻器在电源电路中的应用及其展望

ＺｎＯ压敏电阻器是６０年代末期研制成功的新型过电压保护元件。本文就ＺｎＯ压敏电阻器的特性及其抑制过电压原理，分析了电源电路产生过电压的原因及其对策，得出用ＺｎＯ压敏电阻器抑制过电压是一种较为理想的方法，它具有保护效果好、可靠性高、节能、价廉等一系列优点。文中还就如何应用ＺｎＯ压敏电阻器来保护电源线路、变压器、半导体整流元件、电气电子机器和家电等，给出了保护电路、选用原则和使用注意事项。目前ＺｎＯ压敏电阻器已有成功地应用于某些电源电路的过电压保护的实例，并取得了明显的经济效益。可以预料，ＺｎＯ压敏电阻器将是电源设计者和使用者不可缺少的新型浪涌吸收元件，将广泛地应用于各类电源电路的保护。     

液相掺杂法可提高ZnO压敏电阻器的性能

用液相掺杂法制备的粉体制成了ＺｎＯ压敏电阻器。ＳＥＭ测试分析及密度测试结果证明,瓷片的微观结构得以改善,从而提高了ＺｎＯ压敏电阻器的性能,其中非线性系数达到６７,通流能力为传统法制作的ＺｎＯ压敏电阻器的２倍。     

液相掺杂对ZnO压敏电阻器性能的影响

采用Ｃｏ、Ｍｎ、Ａｌ等元素液相掺杂，制得了高能和高压ＺｎＯ压敏电阻器，通过与氧化物掺杂制得的电阻进行比较，结果表明，掺同样含量Ｃｏ时，液相掺杂的高能压敏电阻器大电流区的Ｉ－Ｖ曲线上翘，将Ｃｏ的含量减半，得到了性能全面优于氧化物掺杂的高能压敏电阻器。在高压ＺｎＯ压敏电阻器配方中，采用Ａｌ液相掺杂，能有效地改善大电流区的非线性。     

籽晶法制备低压ZnO压敏电阻器

研究了ＺｎＯ籽晶粒度、掺入量及其制备方法对压敏电压的影响。实验结果表明：掺入适量粒度合适的籽晶，勿需在高温下长时间烧结，也可制成压敏电压较低，漏电流较小的ＺｎＯ压敏电阻器。     

SrTiO_3环形压敏电阻器

以ＳｒＴｉＯ_３为主晶相，以Ｌａ_２Ｏ_３为施主杂质，在还原气氛下烧结使其充分半导化；掺杂多种金属氧化物，通过高温氧化处理形成晶界层，研制出环形压敏电阻器。其性能优于原有的ＺｎＯ环形压敏电阻器，不仅压敏特性优良，且具有很高的电容量，是一种双功能元件。更重要的是解决了ＺｎＯ压敏电阻器固有的在焊接挂锡后电压降低严重的问题。该成果填补了国内空白，并于１９９２年通过机电部设计定型鉴定。     

SnO2压敏材料势垒电压的测量

依照缺陷势垒模型,将压敏电阻器视为双向导通的二极管,应用半导体理论对低电压情况下的电流－电压关系数据进行了处理,得到了ＳｎＯ２－ＺｎＯ－Ｎｂ２Ｏ５压敏材料的势垒电压。选取的４个测量温度得到的结果是相同的,保证了实验结果的正确性。     

环形压敏电阻器的导电模型

通过表面涂敷Ｉｎ－Ｇａ合金测量压敏电压和试样电阻率等实验手段，研究了ＺｎＯ和ＳｒＴｉＯ３两种环形压敏电阻器的导电行为，得到了二者的导电模型。分析了导电模型不同的原因，并给出简单的鉴别方法。     

Nb2O5掺杂对ZnO压敏电阻器电性能的影响

本文研究了Ｎｂ＿２Ｏ＿５掺杂以及Ｎｂ＿２Ｏ＿５与ＺｎＯ煅烧对ＺｎＯ压敏电阻器电性能的影响。实验表明，Ｎｂ＿２Ｏ＿５的掺入使压敏电场减少，当Ｎｂ＿２Ｏ＿５含量为０．１％ｍｏｌ时，其压敏电场最小．非线性系数最大。煅烧温度越高，压敏电场越高，非线性系数越大。     

ZnO/ZnS核/壳纳米结构的形态及其演变模式

用两步生长的方法在醋酸锌和六亚甲基四胺水溶液中生长ZnO纳米棒阵列,然后以ZnO纳米棒阵列为模板,在Na2S水溶液中硫化0.5～6 h形成ZnO/ZnS纳米结构.用XRD,SEM和TEM表征了ZnO/ZnS核/壳纳米结构的晶体结构、表面形貌.研究了ZnO/ZnS核/壳纳米结构的形态及其转变的模式.在硫化过程中,ZnO首先形成ZnO/ZnS核/壳纳米棒,随着硫化程度的增强,核/壳结构顶部出现空洞,空洞扩展形成管状结构,进一步硫化,管状结构坍塌.硫化形成的ZnO/ZnS结构的形态不仅依赖于初始纳米棒的直径大小和硫化时间的长短,还依赖于纳米棒的分布密度.     

利用光电子能谱研究氧化锌压敏电阻界面电输运特性

采用X射线光电子能谱(XPS)对比分析纯氧化锌陶瓷和氧化锌压敏电阻的界面特性。结果表明,纯氧化锌陶瓷晶粒平均尺寸小于10 祄,掺杂材料有利于ZnO晶粒均匀生长。界面上O/Zn原子数量比值等于2.58,但界面势垒不到10 mV,其体电阻率在2.36~47.97佟m。价电子谱发现:室温下仅纯ZnO费米能级附近有载流子分布,这表明:压敏电阻界面有陷阱态,氧化锌压敏电阻界面电输运特性需用载流子陷阱对双肖特基势垒进行补充。     

一维WO3-ZnO异质结构的合成及生长机理研究

本文采用两步水热法成功合成出一维WO3-ZnO分级异质结构.TEM表征发现ZnO纳米棒在WO3纳米带表面均匀排列,ZnO纳米棒和WO3均各自沿着[0001]方向生长,且二者之间存在特定的取向关系,即生长方向成44°或者136°角.晶体学分析表明在ZnO和WO3之间存在失配度很小的取向关系,即(0001)WO3//(1(1)02)ZnO和(11(22))WO3//(0001)ZnO,以及经过翻转后出现的(0001)WO3//(1(1)02)ZnO和(11(2)2)WO3//(0001)ZnO.根据实验和晶体学分析结果,本文认为ZnO棒在WO3纳米带上的生长机理是符合Volmer-Weber模型的外延生长.     

Effect of Interface Regions on the Thermoelectric Properties of Alternating ZnO/ZnO:Al Stripe Structures

A series of bar-shaped samples consisting of lateral arrangements of alternating ZnO:Al and ZnO stripes was fabricated by radiofrequency (RF)-sputtering and microfabrication techniques on glass substrates. Throughout the series, the number of interfaces between ZnO and ZnO:Al was varied whilst the material fractions of ZnO:Al and ZnO within the bars were not altered. Lateral thermoelectric transport parameters, i.e., Seebeck effect and electrical resistivity, were measured as a function of temperature for all microstructured samples and two reference samples of ZnO:Al and undoped ZnO. The transport direction through the bar was perpendicular to the stripe direction, such that the electrons and phonons have to pass all interfaces. The transport coefficients of the microstructured samples show clear dependence on the number of interfaces between ZnO and ZnO:Al. Thermoelectric measurements, photoluminescence, and Raman measurements indicate that this is due to diffusion of Al donors along the grain boundaries into the undoped ZnO stripes, which takes place during the fabrication process. Modeling of the dependence of the Seebeck coefficient and the resistivity of the series of samples on the basis of a network model accounting for donor diffusion supports these findings.     

Study of optical and dielectric properties of annealed ZnO nanoparticles in the terahertz regime

The frequency-dependent optical and dielectric properties of annealed ZnO nanoparticles in the range of 0.1 to 0.9 THz are studied by using terahertz time-domain spectroscopy（THz-TDS）.The refractive index,power absorption and complex dielectric constants are obtained and the experimental results are well fit with a simple effective medium theory in conjunction with a pseudo-harmonic model.This study reveals that annealed ZnO nanoparticles exhibit the similar phonon response characteristics to the single ZnO crystal and other ZnO nanostructures,such as tetrapods and nanowires.     

Aligned arrays of zinc oxide nanorods on silicon substrates

Experimental data on the elemental vapor-phase synthesis of aligned arrays of ZnO nanorods on Si substrates are summarized. A model of the self-catalytic growth of ZnO nanorods via the vapor-liquid-crystal mechanism, in which liquid Zn droplets serve as a catalyst for oriented growth, is presented. The method developed in the study provides a means for the deposition of aligned arrays of ZnO nanorods onto differently oriented Si substrates without the preliminary deposition of a metal catalyst film or a thin layer of ZnO nuclei. The influence of various factors on the growth rate, dimensions, shape, and ordering of ZnO nanorods is considered. The ZnO nanorods produced in the study are high-purity single crystals with a low content of point defects and, thus, are suitable for practical use in optoelectronics as well as in sensor and microsystem technologies.     

Photoluminescence study of ZnO varistor stability

Photoluminescence (PL) measurements were carried out on commercial ZnO varistor samples that were electrically stressed and/or annealed at different temperatures. Changes in the intensity of green and yellow luminescence centers were studied as a function of annealing treatment. It was found that the ZnO luminescence (green and yellow) decrease with increase in annealing temperature, reach a minimum at 700°C, and increase again beyond 800°C. Furthermore, these green and yellow luminescence bands observed in the PL spectra are quenched in the ZnO varistor samples, compared to pure ZnO. In an electrically stressed ZnO varistor sample, the luminescence intensity was found to be higher compared to the as-sintered varistor sample. Annealing of the stressed varistor sample resulted in a decrease of the luminescence intensity. These PL observations are consistent with previous deep level transient spectroscopy and doppler positron annihilation spectroscopy results. All of the experimental results are consistent with the ion migration model of degradation and can be explained using a grain boundary defect model.     

A New Approach to Model‐Based Simulation of Disordered Polymer Blend Solar Cells

The 3D nanomorphology of blends of two different (organic and inorganic) solid phases as used in bulk heterojunction solar cells is described by a spatial stochastic model. The model is fitted to 3D image data describing the photoactive layer of poly(3‐hexylthiophene)‐ZnO (P3HT‐ZnO) solar cells fabricated with varying spin‐coating velocities. A scenario analysis is performed where 3D morphologies are simulated for different spin‐coating velocities to elucidate the correlation between processing conditions, morphology, and efficiency of hybrid P3HT‐ZnO solar cells. The simulated morphologies are analyzed quantitatively in terms of structural and physical characteristics. It is found that there is a tendency for the morphology to coarsen with increasing spin‐coating velocity, creating larger domains of P3HT and ZnO. The impact of the spin‐coating velocity on the connectivity of the morphology and the existence of percolation pathways for charge carriers in the resulting films appears insignificant, but the quality of percolation pathways, considering the charge carrier mobility, strongly varies with the spin‐coating velocity, especially in the ZnO phase. Also, the exciton quenching efficiency decreases significantly for films deposited at large spin‐coating velocities. The stochastic simulation model investigated is compared to a simulated annealing model and is found to provide a better fit to the experimental data.     

Strong Enhancement of Near-Band-Edge Photoluminescence of ZnO Nanowires Decorated with Sputtered Metallic Nanoparticles

The effect of the Ar plasma during metal deposition on the photoluminescence (PL) of metal-coated ZnO nanowires (NWs) has been investigated. Strong enhancement of near-band-edge emission (NBE) is observed for ZnO NWs coated with Al and Ni nanoparticles (NPs) by radiofrequency magnetron sputtering, while the samples coated with NPs by e-beam evaporation show quenching of the PL intensity. A model is proposed that satisfies the observed experimental results and assigns the strong enhancement of the NBE PL of ZnO NWs to excitons bound to structural defects in the surface layer of the ZnO NWs.     

厚度对Si衬底上生长的ZnO薄膜性能的影响

采用金属有机化学气相沉积方法,在Si(100)衬底上生长出具有高度C轴择优取向的ZnO薄膜.通过X射线衍射、原子力显微镜和室温光致发光谱研究了厚度对ZnO薄膜的结构、表面和光学性能的影响.X射线衍射图显示ZnO薄膜只有单一的(0002)峰,具有高度择优取向.AFM和PL测试表明,在取样薄膜厚度范围内,薄膜的表面质量和发光性能没有随着薄膜厚度的增加而提高.这是因为薄膜在厚度增加的生长过程中,生长模型变化且晶粒增大.