溶胶凝胶法制备VO2薄膜的组织与性能研究

采用V2O5熔体淬水制成胶体，并浸涂于不同的基片上，分别用于电阻检测和组织结构分析。经过真空加热分解V2O5凝胶薄膜，得到了具有相变特性的VO2薄膜。在真空热处理温度为500℃，时间为34h，真空气压为2Pa，得到的VO2相变薄膜电阻突变量级达3.4，相变温度在67℃左右。另外，TEM组织观察表明，VO2薄膜为多晶组织，VO2薄膜晶粒尺寸对电阻突变量级影响较大。晶粒尺寸增加，电阻突变量级增大。VO2晶界对相变有阻碍作用。     

离子注入条件下单晶银薄膜形成的理论探讨

在室温环境下，用不同的注入剂量将２４ｋｅＶ的Ｎ＋离子和３５０ｋｅＶ的Ｘｅ＋离子注入进多晶银薄膜中。对实验结果进行分析后发现，经离子注入后在银薄膜中出现了再结晶和晶粒长大现象。当注入的离子达到一定剂量时，多晶银薄膜转变成单晶银薄膜．本文对单晶银薄膜的形成机理作了探讨，认为与晶粒生长有关的主要因素是：（１）离子注入．过程中在薄膜内部产生的高密度的缺陷和位错促进了晶粒再结晶和晶粒生长。（２）由于晶格畸变而产生的界面张力为在晶粒初始再结晶以后的进一步长大提供了驱动力。（３）晶粒之间的取向差有助于晶粒的生长。（４）离子注入过程中产生的晶格弛豫效应促使薄膜中的应变能不断恢复和产生，使晶粒持续不断地再结晶而逐渐长大。（５）薄膜的基底对单晶薄膜的形成有一定影响。     

硫化时间对电沉积制备FeS2薄膜组织与结构的影响

利用电沉积及热硫化法制备了FeS2 多晶薄膜,研究了不同硫化时间对FeS2 薄膜形成过程的影响。结果表明采用Na2S2O3 和FeSO4 水溶液电沉积和150~ 200℃处理可以制备多孔Fe3O4 薄膜,再经400℃、80kPa硫化处理,Fe3O4 可转变成FeS2 多晶薄膜。随硫化时间延长到10h,FeS2 的晶格常数减小而晶粒粗化,再继续延长硫化时间,FeS2 的晶格常数增大而晶粒尺寸下降。可以用点缺陷浓度、相变应力及亚晶界运动等因素分析Fe3O4 向FeS2 转变过程中的微观组织参数变化规律。     

沉积温度对Gd掺杂CeO2电解质薄膜生长及电学特性的影响

采用反应射频磁控溅射技术,在非晶石英衬底上不同温度下制备了纳米多晶Gd掺杂CeO2(简称GDC)氧离子导体电解质薄膜,采用X射线衍射仪、原子力显微镜对薄膜物相、晶粒大小、生长形貌进行了表征,利用交流阻抗谱仪测试了GDC薄膜的电学性能.结果表明,GDC薄膜生长取向随沉积温度而变化:300-400℃时为强(111)织构生长,而500-600℃时薄膜趋于无规则生长;随着沉积温度的升高,薄膜的牛长形貌由同一取向的大棱形生长岛转变为密集球形小生长岛;GDC多晶薄膜的电导活化能约为1.3eV,接近于晶界电导活化能值,说明GDC交流阻抗主要源于晶界的贡献;晶界空间电荷效应导致GDC薄膜电导率随晶粒尺寸而变化,晶粒尺寸越小,电导率越大.     

硫化压力对电沉积并硫化合成的FeS2薄膜组织结构的影响

采用电沉积及400℃不同压力硫化热处理制备了多晶FeS2薄膜,研究了硫化压力对薄膜晶体结构及微观组织的影响。在较低的硫化压力条件下,电沉积得到的Fe3O4先驱体硫化反应不充分,薄膜组织中FeS2与Fe3O4共存。当硫化压力高于20kPa时,Fe3O4先驱体可充分地转变成具有细小晶粒形态的FeS2,薄膜形貌也由多孔疏松演变为均匀平整。硫化压力在5～40kPa范围内变化对FeS2晶粒尺寸影响不明显,但使FeS2晶格常数略有下降。     

薄膜生长基底对FeS2晶体取向的影响

用Fe膜硫化法制备了FeS2薄膜,分析了基底对FeS2薄膜晶体结构和位向分布的影响.结果表明,改变基底晶体的类型能够在一定程度上控制FeS2薄膜的晶体位向分布.FeS2薄膜在Si(100)、Si(111)和Al基底上可获得(200)方向的择优取向,在TiO2基底上可同时获得(200)及(220)择优取向,非晶玻璃基底对位向分布影响不明显.不同的基底与Fe薄膜的界面错配度不同,可改变薄膜晶体位向的分布,导致晶格畸变程度和晶粒尺寸的变化.当基底为非晶结构或界面的错配度较大时,FeS2晶体的取向分布主要受表面能和晶粒优先生长方向的控制,薄膜具有较小的晶格畸变和较细的晶粒;当基底为晶态并且界面错配度较小时,FeS2晶体取向的分布除受表面能及晶粒优先生长方向控制外,还受界面应变能的控制,此时薄膜易形成较大的晶格畸变和粗晶粒.     

溶胶-凝胶方法制备BiFeO_3薄膜的微结构和晶粒尺寸效应

使用溶胶凝胶法在Pt/Ti/SiO_2/Si衬底上生长不同厚度与不同稀土掺杂(Nd,Ce,La)的BiFeO_3(BFO)薄膜,高分辨X射线衍射实验结果表明薄膜是由无择优取向的多晶成份组成,不同厚度和掺杂的薄膜都呈现三方相。对比不同厚度BF0薄膜的结构发现,随着薄膜厚度的增加,薄膜的晶粒尺寸呈现增大的趋势,同时晶格常数也随之增大;比较不同掺杂的薄膜,发现随掺杂原子的离子半径增大(Nd,Ce,La),薄膜的晶粒尺寸随之减小,同时薄膜的晶格参数变小。这些结果表明在BFO薄膜中存在晶粒尺寸效应,BFO的晶格随着晶粒尺寸的增大而增大。     

玻璃衬底和Si衬底制备的Zn0.96Nd0.04O薄膜的结构研究

通过射频磁控溅射技术在玻璃衬底和Si（111）村底上制备了Zn0.96Nd0.04O薄膜。XRD分析表明,Zn0.96Nd0.04O薄膜是具有C轴择优生长的纳米多晶薄膜,Nd以替位原子的形式存在于ZnO晶格,Nd掺杂没有改变ZnO晶格结构。从AFM图中看出,薄膜表面形貌较为粗糙,Si衬底薄膜的晶粒具有规律且晶粒尺寸大于玻璃衬底。     

直流反应磁控溅射法制备VO_2薄膜

VO2是一种相变材料.发生相变时,VO2的电阻、透过率、反射率都会发生显著的变化;反应磁控溅射法是制备VO2薄膜的一种比较理想的方法.文中,重点讨论氧氩气质量流量比m(O2)/m(Ar)、基片温度以及沉积后薄膜的退火处理对制备薄膜成分、结构和性能的影响.通过分析得出m(O2)/m(Ar)比在113和112间具有较高的VO2含量;基片温度在250℃时具有较佳的VO2结晶特性;450 ℃保持2 h的真空退火处理可以改变薄膜成分和结构,使高价的V2O5薄膜还原到四价的VO2,且明显减少薄膜的氧缺陷,提高氧原子的含量,减少空洞,增加晶粒尺寸提高膜的致密度.     

非晶硅薄膜晶化方法

多晶硅薄膜由于具有较高的载流子迁移率和良好的光电性能,广泛应用于集成电路及光电器件中,尤其在太阳电池领域引起了广泛关注。多晶材料晶界处会发生载流子的复合,降低载流子寿命。结晶度与晶粒尺寸是多晶硅薄膜取得良好性能的关键因素,直接制备的多晶硅薄膜一般晶粒尺寸较小、晶界较多,所以常采用非晶硅晶化法制备出晶粒尺寸较大的多晶硅薄膜。介绍了几种常见的非晶硅薄膜晶化方法,总结了各种晶化方法的机理和制备的薄膜的物理性质。     

二氧化钒薄膜在α-Al2O3衬底上的外延生长及其金属-半导体相变特性研究

利用ＸＲＤ及ＸＲＤ极图技术表征了用激光剥离技术生长的ＶＯ_２薄膜．结果表明：在衬底温度为５００℃,氧气偏压６．６７Ｐａ的条件下,在Ａｌ_２Ｏ_３（１１２０）衬底上能实现ＶＯ_２的二维外延生长．薄膜的结构除了与沉积工艺有关外,还和衬底的取向密切相关．在Ａｌ_２Ｏ_３（１１２０）衬底上,定向生长的（１００）ＶＯ_２在Ｍｉｌｌａｒ指数＜５时,除了［０１０］以外,不存在其他晶格矢量与衬底相匹配,从而不可能实现三维单晶薄膜的外延生长．电学特性的测试结果显示,在温度为６５℃左右,ＶＯ_２薄膜出现相交,薄膜的电阻率变化达４个数量级．     

晶粒尺寸对氧化钒薄膜电学与光学相变特性的影响

采用直流对靶磁控溅射方法制备氧化钒薄膜,通过改变热处理温度获得了具有不同晶粒尺寸的相变特性氧化钒薄膜,对氧化钒薄膜相变过程中电阻和红外光透射率随温度的突变性能进行研究.结果表明:经300℃和360℃热处理后,薄膜内二氧化钒原子分数达到40%,氧化钒薄膜具有绝缘体-金属相变特性,薄膜的晶粒尺寸分别为50nm和100nm;...     

VO2（M）控温包装薄膜制备的研究进展

二氧化钒(VO_2)纳米颗粒具有多种晶型结构,其单斜型半导体M相(VO_2(M))在接近室温时具有完全可逆的相转变性质,相变为四方金红石金属R相,从而引起光学性能的急剧变化,因而VO_2(M)可作为良好的阻热材料应用于控温包装薄膜领域。综述了VO_2(M)纳米颗粒和控温包装薄膜的制备方法,展望了VO_2(M)控温包装薄膜的研究方向。VO_2(M)纳米颗粒的传统制备方法有一步水热法和热分解法等,近年来也出现了新型制备方法,如籽晶诱导法和火焰燃烧法等;控温包装薄膜主要的制备方法为气相法和液相法。根据不同产品的温度需求,通过改变原料种类、温度及掺杂元素等工艺参数调节VO_2(M)纳米颗粒的相变温度,可制备出不同相变温度的VO_2控温包装薄膜。VO_2(M)控温包装薄膜作为一种高新科技产物,可以有效调控商品运输和储藏过程中包装内氛围,具有广阔的应用前景。     

Reactive pulsed-DC sputtered Nb-doped VO2 coatings for smart thermochromic windows with active solar control

Thermochromic VO2 thin films have successfully been grown on SiO2-coated float glass by reactive pulsed-DC magnetron sputtering. Different Nb doping amounts were introduced in the VO2 solid solution during the film growing which resulted in films with distinct semiconducting-metal phase transition temperatures. Pure VO2 showed improved thermochromic behavior as compared with VO2 films prepared by conventional DC sputtering. The transition temperatures were linearly decreased from 59 down to 34 degrees C with the increase in Nb content. However, the luminous transmittance and the infrared modulation efficiency were markedly affected. The surface morphology of the films was examined by scanning electron microscopy (SEM) and showed a tendency for grain sized reduction due to Nb addition. Moreover, the films were found to be very dense with no columnar microstructure. Structural analyses carried out by X-ray diffractometry (XRD) revealed that Nb introduces significant amount of defects in the crystal lattice which clearly degrade the optical properties.     

钨掺杂二氧化钒薄膜的THz波段相变性能的研究

通过溶胶–凝胶法制备纯的VO₂和W掺杂的VO₂薄膜, 并且进行了XPS、AFM和XRD的分析与表征, 并观察了其微观形貌和结构. 同时研究了VO₂和W掺杂VO₂在红外光谱(λ=4 μm)和THz(0.3~1.0 THz)区域的金属–绝缘转变性能. 结果表明: 室温下W掺杂的VO₂薄膜在红外和THz区域的初始透过率都比纯的VO₂薄膜低. 在THz波段, W掺杂的VO₂表现出更低的相变温度. 同时在VO₂和W掺杂VO₂相变过程中, 观察到了金属–绝缘转变和结构转变的现象, W掺杂VO₂具有明显的峰位偏移现象.     

Dependence of the longitudinal strain coefficient of resistivity of silver films on thickness and grain size diameter

A grain boundary model modified by including the Fuchs size effect has been used to derive a general expression for the longitudinal strain coefficient of resistivity of continuous polycrystalline silver films, of thickness greater than the intrinsic mean free path, in terms of the grain size diameter and the film thickness. It has been found that the longitudinal strain coefficient of film resistivity has zero value for very small grain size and attains the bulk value when the grain size and the film thickness are very large. It has also been found that a threshold value of the grain size diameter exists, below which the film thickness has practically no effect on the strain coefficient of film resistivity. However, for grain size diameters greater than the threshold value, thicker films have values of the strain coefficient or resistivity higher than those for thinner films.     

Description of electronic transport properties of monocrystalline films by a statistical model

Grain boundaries in monocrystalline films are represented by a two- dimensional array of scatterers. The effects of electronic scattering are calculated by means of Matthiessen's rule starting from the electronic mean free path related to a particular type of scattering (bulk, grain boundary, external surface).

Theoretical expressions for the film resistivity and its temperature coefficient of resistivity and thermoelectric power are proposed; comparison with previously reported experiments gives a satisfactory fit.     

Stability of nano-thick transparent conducting oxide films for use in a moist environment

The stability of nano-thick transparent conducting oxide thin films in a high humidity environment was investigated. The stability of ITO and impurity-doped ZnO thin films prepared with a thickness in the range from approximately 20 to 100 nm on glass substrates at a temperature below 200 °C by a pulsed laser deposition was evaluated in air at a relative humidity of 90% and a temperature of 60 °C. The resistivity of all Al- and Ga-doped ZnO thin films tested was found to increase markedly with test time, whereas that of ITO remained relatively stable; the stability (resistivity increase) of the doped ZnO thin films was considerably affected by film thickness but was relatively independent of the deposition substrate temperature. In particular, doped ZnO thin films with a thickness below approximately 50 nm were very unstable under the test conditions. The resistivity increase of doped ZnO films is mainly attributed to the grain boundary scattering resulting from the adsorption of oxygen on the grain boundary.     

Structural and resistivity changes in heat-treated chromium-gold films

Chromium-gold films deposited on glass were subjected to heat treatment at temperatures between 280 °C and 450 °C. The resistivity dependence of the conductive gold film with time at temperature exhibits a maximum. The processes controlling the resistivity of the gold film are the diffusion of chromium into the gold and the depletion of chromium from the gold. This latter process is accompanied by the production of Cr₂O₃ on the outer surface of the gold film. Microscope observations suggest that the diffusion of the chromium in the gold takes place through grain boundaries as well as in the lattice until the chromium layer vanishes. The Cr₂O₃ first forms as a polycrystalline film. With further diffusion large discrete single crystals of Cr₂O₃ are observed on the gold film surface.     

Resistivity and structure of evaporated polycrystalline molybdenum films

Molybdenum films of thickness 20–2600 nm were evaporated at a substrate temperature of 650°C and were then vacuum annealed at 900°C. The mean grain size of films increased with increasing thickness and it became saturated at about 130 nm for films thicker than 1000 nm. Using this result, the Mayadas-Shatzkes model of grain boundary scattering was used for the interpretation of the observed thickness dependence of the resistivity of the films. Values of the grain boundary electron reflection coefficient, which increase with decreasing film thickness, were used to fit the experimental data to theoretical curves.