Deposition of TiO2 films by magnetron sputtering and fabrication of MSM ultraviolet photodetectors

紫外辐射探测技术可以应用在太阳紫外线监测、火焰探测、生物学研究、紫外天文学以及无线通信等许多领域，现在已经开始受到广泛的重视。SiC、GaN和ZnO等宽禁带半导体材料紫外光电探测器具有“可见光盲”和室温工作等特点，因此得到较为充分地研究和应用，但是它们同时存在价格昂贵和制作工艺复杂等问题。TiO2同样是宽禁带半导体材料，锐钛矿结构的TiO2禁带宽度为3.2eV，有可能实现探测器的“可见光盲”特性，同时这种材料还具有优秀的物理、化学和光学性质。射频磁控溅射技术可以溅射化学配比理想的TiO2靶材，从而使生长的薄膜具有好的化学计量比，另外该技术制备的TiO2薄膜具有良好的均匀性和致密度，薄膜与衬底附...Detection of Ultraviolet (UV) radiation is becoming increasingly important in a number of fields, such as solar UV monitoring, flame sensor, and biological research, as well as in UV astronomy and secure space-to-space communication. UV photodetectors (PDs) based on the wide bandgap semiconductors, such as SiC, GaN, and ZnO, show excellent wavelength selectivity (“visible-blindness”) and possibili...学位：理学博士院系专业：物理与机电工程学院物理学系_凝聚态物理学号：1982008015050

Structural,Electrical,and Optical Properties of Transparent Conductive Al-Doped ZnO Films Prepared by RF Magnetron Sputtering

室温下采用RF磁控溅射技术在石英衬底上制备了多晶ZnO:Al(AZO)透明导电薄膜,通过XRD,AFM,AES,Hall效应及透射光谱等测试研究了RF溅射功率、氩气压强对薄膜的结构、电学和光学性能的影响.分析表明:在最优条件下(溅射功率为250W,氩气压强为1.2Pa时),180nmAZO薄膜的电阻率为2.68×10-3Ω.cm,可见光区平均透射率为90%,适合作为发光二极管和太阳能电池的透明电极.所制备的AZO薄膜具有c轴择优取向,晶粒间界中的O原子吸附是限制薄膜电学性能的主要因素.Highly conductive transparent Al-doped zinc oxide(AZO)films with highly(002)-preferred orientation were successfully deposited on glass substrates at room temperature by RF magnetron sputtering.Optimization of deposition parameters was based on sputtering RF power and Ar pressure in the vacuum chamber.AZO films of 180nm with an electrical resistivity as low as 2.68×10-3 Ω·cm and an average optical transmission of 90% in the visible range were obtained at RF power of 250W and Ar pressure of 1.2Pa.The effect of chemisorption of oxygen on the grain boundary would capture electrons from conduction band and lead the formation of potential barriers among the crystallites,which will influence the electric property of the AZO thin films.The films have satisfactory properties of low resistance and high transmittance for application as transparent conductive electrodes in light emitting diodes(LEDs)and solar cells

Effect of RF power on the structure and properties of ZnO∶Al films deposited by magnetron sputtering

采用RF磁控溅射技术以ZnO:Al2O3(2 wt%Al2O3)为靶材在石英玻璃衬底上制备多晶ZnO:Al(AZO)薄膜,通过XRD、AFM、AES以及Hall效应、透射光谱、折射率等手段研究了RF溅射功率(50~300 W)对薄膜的组织结构和电学,光学性能的影响。分析表明:所制备的AZO薄膜具有c轴择优取向,并且通过对不同功率下薄膜载流子浓度与迁移率的研究发现对于室温下沉积的AZO薄膜,晶粒间界中的O原子吸附是影响薄膜电学性能的主要因素。同时发现当功率为250 W时薄膜的电阻率降至最低(3.995×10-3Ω.cm),可见光区平均透射率为91%。Aluminum doped zinc oxide films are deposited by magnetron sputtering using a zinc oxide target doped with Al2O3(2 wt%.) with different RF powers on quartz substrate.The structural and compositional characteristics of the films are investigated by XRD,AFM,SEM,AES and XPS.respctively,while the electrical and optical properties of the thin films are studied by the Hall measurement and spectrophotometry,respectively.It has been found that all films deposited are c-axis preferred orientation perpendicular to the substrate with porous crystalline structure.The lowest resistivity obtained in this study is 3.9×10-3 Ω·cm for the film deposited at 250 W,and the average transmittance is 91% in the visible range.By comparing the samples deposited at various RF power,the oxygen absorption in the grain boundaries is the dominant factor which influences the electrical property of the AZO thin film

Design and Fabrication of Al_2O_3/SiO_2 Double-Layer Antireflection Coatings on 4H-SiC Substrate

在4H-SiC基底上设计并制备了Al2O3/SiO2紫外双层减反射膜,通过扫描电镜(SEM)和实测反射率谱来验证理论设计的正确性。利用编程计算得到Al2O3和SiO2的最优物理膜厚分别为42.0nm和96.1nm以及参考波长λ=280nm处最小反射率为0.09%。由误差分析可知,实际镀膜时保持双层膜厚度之和与理论值一致有利于降低膜系反射率。实验中应当准确控制SiO2折射率并使Al2O3折射率接近1.715。用电子束蒸发法在4H-SiC基底上淀积Al2O3/SiO2双层膜,厚度分别为42nm和96nm。SEM截面图表明淀积的薄膜和基底间具有较强的附着力。实测反射率极小值为0.33%,对应λ=276nm,与理论结果吻合较好。与传统SiO2单层膜相比,Al2O3/SiO2双层膜具有反射率小,波长选择性好等优点,从而论证了其在4H-SiC基紫外光电器件减反射膜上具有较好的应用前景。Al2O3/SiO2 double-layer UV antireflection coatings were designed and fabricated on 4H-SiC substrate,and the validity of theoretical design was further verified by scanning electron microscope (SEM) and reflection spectrum. The optimal physical thickness of Al2O3 and SiO2 is 42.0 nm and 96.1 nm respectively by programming calculation. And then the minimum reflectance of 0.09% is obtained at reference wavelength λ=280 nm. According to error analysis,keeping the sum of double-layer thickness consistent with theoretical value is helpful to reduce the reflectance. In addition,the refractive index of SiO2 should more accurate and the refractive index of Al2O3 should be controlled close to 1.715 in the experiment. Al2O3/SiO2 double-layer coatings were deposited on 4H-SiC substrate by electron beam evaporation and the physical thickness is 42 nm and 96 nm respectively. SEM images show that the deposited layers and the substrate perform good adhesion to each other. The practical minimum reflectance is 0.33% at λ=276 nm which is close to theoretical value. Compared with conventional SiO2 single layer,Al2O3/SiO2 double-layer coatings show low reflectance and better wavelength selectivity. These results make the possibility for 4H-SiC based UV optoelectronic devices with Al2O3/SiO2 films as antireflection coatings

Methods For Measuring Dynamic Characteristics of Rolling Element Bearings

轴承的动力特性对转子-轴承系统的动力特性有重要的影响。但至今，滚动轴承的动力特性仍缺乏系统的资料，在许多情况下，将滚动轴承简化为无阻尼的定常弹性元件。本文分析了滚动轴承动力特性的主要影响因素，介绍了滚动轴承动力特性的两种测试方法，并以某航空轴承为例作了具体测试，取得了比较一致的结果。本文提出的方法可作为建立滚动轴承动力特性数据库的基本手段。The dynamic characteristics of the bearings have a considerable inFluence on the dynamic characteristics of a rotor bearing system.So Far,there are Few materials concerning the dymamic characteristics of the rolling element bearings.In many cases,a rolling element bearing is simpliFied as an undamped element with constant stiFFness coeFFicient.In this paper,the primary inFluence Factors to the rolling element bearings have been analyzed.Two methods For measuring the dynamic characteristics of the bearings have been introduced.The dynamic characteristics of a ball bearing used in aeroengine have been measured on two test rigs.The results measured From the two rigs are quite coincident with each other.The methods presented in the paper can be used as the basic means For creating the database of dynamic characteristics of the bearings

Effect of Ar Pressure on the Structure and Properties of ZnO∶Al Films Deposited by RF Magnetron Sputtering

以ZnO∶Al2O3为靶材在石英玻璃衬底上射频磁控溅射制备多晶ZnO∶A l(AZO)薄膜,通过XRD、AFM以及H all效应、透射光谱等测试研究了RF溅射压强对薄膜结构、电学与光学性能的影响。分析表明:所制备的薄膜具有c轴择优取向,当压强为1.2Pa时薄膜的电阻率降至最低(2.7×10-3Ω·cm)。薄膜在可见光区平均透射率高于90%,光学带隙均大于本征ZnO的禁带宽度。Aluminum doped zinc oxide films were deposited by RF magnetron sputtering using a zinc oxide target doped with Al2O3 with different Ar pressure.The structural characteristics of the films were investigated by XRD and AFM while the electric and optical properties of the thin films were studied by the Hall measurement and optical spectroscopy,respectively.All of the films deposited were c-axis preferred orientation perpendicular to the substrate.The lowest resistivity obtained in this study was for the film deposited at Ar pressure of 1.2Pa,and the average transmittance is larger than 90% in the visible range for all samples.The optical band gap of the films is in the range of 3.53—3.66eV which is larger than the band gap of intrinsic ZnO

High quality Multi Quantum Well Structure by MOVPE

【中文摘要】 利用金属有机气相沉积技术生长ＩｎＧａＡｓＰ／ＩｎＰ多量子阱结构，通过改变生长程序，得到了优化的陡峭量子阱界面．并利用光致发光（ＰＬ）和Ｘ射线双晶衍射对其界面质量分析，Ｘ射线双晶衍射表明界面起伏为一个原子层厚度，在１０Ｋ温度下ＰＬ谱半峰高宽（ＦＷＨＭ）为７ｍｅＶ 【英文摘要】 Multi quantum well interface quality is one of key factors that affect device performance. Metalorganic vapor phase epitaxial (MOVPE) grown InGaAsP/InP multi quantum well structure are studied. Abruptness optimization of interfaces is carried out by means of a different gas switching sequences. Analysis of x-ray and photoluminescence (PL) are used to provide detailed information about the interfaces. Measured and simulated rocking curves of Xray diffraction show monolayer fluctuations at the interfaces...福建省青年重点基