Morphology and texture evolution of nanostructured CaF2 films on amorphous substrates under oblique incidence flux

The morphology and biaxial texture of vacuum evaporated CaF(2) films on amorphous substrates as a function of vapour incident angle, substrate temperature and film thickness were investigated by scanning electron microscopy, x-ray pole figure and reflection high energy electron diffraction surface pole figure analyses. Results show that an anomalous [220] out-of-plane texture was preferred in CaF(2) films deposited on Si substrates at < 200?°C with normal vapour incidence. With an increase of the vapour incident angle, the out-of-plane orientation changed from [220] to [111] at a substrate temperature of 100?°C. In films deposited with normal vapour incidence, the out-of-plane orientation changed from [220] at 100?°C to [111] at 400?°C. In films deposited with an oblique vapour incidence at 100?°C, the texture changed from random at small thickness (5 nm) to biaxial at larger thickness (20 nm or more). Using first principles density functional theory calculation, it was shown that [220] texture formation is a consequence of energetically favourable adsorption of CaF(2) molecules onto the CaF(2)(110) facet.     

深紫外宽入射角范围增透膜设计与制备

在大数值孔径深紫外光学系统中,需要使用宽入射角范围的增透膜光学元件.选择LaF3和MgF2两种镀膜材料,设计了适用于深紫外宽入射角范围的三层、五层和七层三种增透膜系.实验使用热舟蒸发在熔融石英基底上镀制了设计的薄膜,并用紫外分光光度计对其光谱性能进行了测试,得到了在宽入射角范围内具有较高透过率的深紫外增透膜元件.双面镀五层增透膜系的熔石英基片在0°～55°入射角内的剩余反射率小于2.5％,在0°～20°入射角内的透过率大于98％.     

Fabrication of resonant-tunneling diodes by Sb surfactant modified growth of Si films on CaF/sub 2//Si

Molecular beam epitaxy growth of Si thin films on CaF/sub 2//Si(111) substrates has been studied. A surfactant-modified solid-phase epitaxy method, where the room temperature Si deposition was followed by annealing under Sb flux, resulted in a continuous, smooth epitaxial crystalline Si film with a sharp (/spl radic/3/spl times//spl radic/3)R30/spl deg/ reconstruction and a surface roughness of 0.15-nm rms for a 2.8-nm Si thin film. This growth technique was used to fabricate CaF/sub 2//Si/CaF/sub 2/ double-barrier resonant tunneling diodes in SiO/sub 2/ windows patterned on Si(111) substrates. A negative differential resistance (NDR) peak was found at /spl sim/0.35 V at 77 K, and the current density at the NDR peak was estimated to be 3-4 orders of magnitude higher than in earlier reports.     

Radiation damage effects in far-ultraviolet filters, thin films, and substrates

Advances in vacuum ultraviolet thin-film filter technology have been made through the use of filter designs with multilayers of materials such as Al(2)O(3), BaF(2), CaF(2), HfO(2), LaF(3), MgF(2), and SiO(2). Our immediate application for these filters will be in an imaging system to be flown on a satellite where a 2 × 9 R(E) orbit will expose the instrument to approximately 250 krad of radiation. Because to our knowledge no previous studies have been made on the potential radiation damage of these materials in the thin-film format, we report on such an assessment here. Transmittances and reflectances of BaF(2), CaF(2), HfO(2), MgF(2), and SiO(2) thin films on MgF(2) substrates, Al(2)O(3) thin films on fused-silica substrates, uncoated fused silica and MgF(2), and four multilayer filters made from these materials were measured from 120 to 180 nm beforeand after irradiation by 250 krad from a (60)Co gamma radiation source. No radiation-induced losses in transmittance or reflectance occurred in this wavelength range. Additional postradiation measurements from 160 to 300 nm indicates 2-5% radiation-induced absorption near 260 nm in some of the samples with MgF(2) substrates. From these measurements we conclude that far-ultraviolet filters made from the materials tested should experience less than 5% change from exposure to up to 250 krad of high-energy radiation in space applications.     

氨化Si基Ga2O3/Ti制备GaN纳米线

采用磁控溅射技术先在硅衬底上制备Ga2O3/Ti薄膜,然后在950℃时于流动的氨气中进行氨化反应制备GaN薄膜.X射线衍射(XRD)、傅立叶红外吸收光谱(FTIR)、选区电子衍射(SAED)和高分辨透射电子显微镜(HRTEM)的结果表明采用此方法得到了六方纤锌矿结构的GaN单晶纳米线.通过扫描电镜(SEM)观察发现纳米线的形貌,纳米棒的尺寸在50～150nm之间.     

N型Bi2Te2.5Se0.5热电薄膜的电阻率与膜厚和温度的关系

在玻璃衬底上通过瞬间蒸发法沉积了厚度为50-400nm的N型Bi2.5Se0.5热电薄膜,沉积温度为473K.采用XRD、EDXA和FESEM技术分别对薄膜的相结构、组成和表面形貌进行了分析研究,在300-350K的温度范围内,研究了薄膜的电阻率与膜厚和温度的相互关系.     

Influence of ion assistance on LaF3 films deposited by molybdenum boat evaporation

LaF3 thin films at 193 nm were deposited by the molybdenum boat evaporation with ion-assisted deposition (IAD). Various optical characteristics, stress, and microstructures that formed under different ion-beam voltages of IAD deposition were investigated. The relation between these properties is also discussed. LaF3 films deposited with IAD exhibited small rough surfaces and large optical loss at 193 nm. The largest value of optical loss for films at 193 nm, which were prepared at an ion-beam voltage of 400 V, was 1.55% and the extinction coefficient was smaller than 0.0015. Microstructures and crystalline structures of films were influenced and changed by the ion-assisted deposition process. Tensile stress value of films increased as the ion-beam voltage rose. Refractive index, related to the packing density and microstructures, also increased as the ion-beam voltage rose.     

溅射后退火簇状GaN纳米棒的生长及其镁的作用

采用磁控溅射技术先在硅衬底上制备Ga2O3/Mg薄膜,然后在1000℃时于流动的氨气中进行氨化反应制备GaN薄膜.X射线衍射(XRD)、X射线光电子能谱(XPS)、选区电子衍射(SAED)和高分辨透射电子显微镜(HRTEM)的结果表明采用此方法得到了六方纤锌矿结构的GaN单晶纳米棒.通过扫描电镜(SEM)观察发现纳米棒的形貌,纳米棒的直径在200～600nm之间.我们对镁层的作用进行了简单探讨.     

热丝CVD法低温制备的多晶硅薄膜质量对衬底依赖性的研究

以SiH4和H2作为反应气体,采用HWCVD的方法分别在石英玻璃、AZO、Si（100）和Si（111）衬底上制备了多晶硅薄膜。利用X射线衍射（XRD）,拉曼（Raman）光谱和傅里叶红外（FT-IR）吸收光谱研究了不同衬底对多晶硅薄膜的择优取向、晶化率和应力的影响,用SEM观察了多晶硅薄膜的表面形貌。研究发现在4种衬底上生长的多晶硅薄膜均为（111）择优取向。单晶硅片对多晶硅薄膜有很强的诱导作用,并且Si（111）的诱导作用优于Si（100）的诱导作用。AZO对多晶硅薄膜生长也有一定的诱导作用。通过计算薄膜晶态比,得到除以石英为衬底的样品外,其它3种样品的晶态比均在90%以上,尤其以单晶硅片为衬底的样品更高。石英玻璃、AZO和Si（100）上生长的多晶硅薄膜中均存在压应力。     

Atomic layer deposition process with TiF4 as a precursor for depositing metal fluoride thin films

A novel atomic layer deposition process for the preparation of fluoride thin films in a temperature range of 225 degrees C-400 degrees C is introduced. The crystallinity, morphology, composition, thicknesses, refractive indices, and transmittance of the films are analyzed. Low impurity levels are obtained at 350 degrees C-400 degrees C with good stoichiometry. Refractive indices of 1.34-1.42 for MgF(2), 1.43 for CaF(2), and 1.57-1.61 for LaF(3) films are obtained.     

Structural and electrical studies of thermally evaporated nanostructured CdTe thin films

CdTe thin films were deposited on KCl and glass substrates using thermal evaporation technique under high vacuum conditions. CdTe bulk compound grown by vertical directional solidification (VDS) technique was used as the source material to deposit thin films. Powder X-ray diffraction technique was employed to identify the phase of the as grown bulk CdTe compound as well as its thin films. Surface morphology and the stoichiometry of the bulk compound and thin films was carried out by using scanning electron microscope (SEM) with an attachment of energy dispersive spectrometer(EDS). Microstructural features associated with the as deposited CdTe thin films were studied by using transmission electron microscope (TEM). The films deposited on to glass substrates at different temperatures have been used to study the I-V characteristics of the films. These parameters have been studied in detail in order to prepare good quality nanostructured thin films of CdTe compound. CdTe bulk compound grown by VDS method and its thin films prepared by thermal evaporation method found to have single phase with cubic structure. Size of the particles in the as deposited films vary between 5 and 40 nm In the present study efforts have been made to correlate the electrical and optical properties of the CdTe thin films with the corresponding microstructural features associated with them.     

氮化时间对扩镓硅基GaN晶体膜质量的影响

采用射频磁控溅射在扩镓硅基上溅射Ga2O3薄膜,然后氮化反应组装GaN晶体膜,并研究氮化时间对薄膜晶体质量的影响。测试结果表明：采用两步法生长得到六方纤锌矿结构的GaN多晶膜,扩镓硅层有效的抑制了硅衬底的氮化和弛豫了GaN与Si衬底的热失配。同时显示：在相同的氮化温度下,晶粒尺寸随氮化时间的增加而增大,薄膜的晶化程度相应的得到提高。     

不同基底上SiO2薄膜的显微结构和力学性能

用电子束蒸发技术在K9玻璃及两种不同取向的钇铝石榴石(Y₃Al₅O₁₂, 简称YAG)晶体上沉积了SiO₂薄膜, 采用X射线衍射仪和纳米划痕仪对薄膜显微结构和力学性能进行了研究。实验结果表明: 薄膜在K9 、YAG(100) 和YAG(111)基底上分别呈现非晶态和多晶态; 沉积在不同基底上的薄膜的弹性模量并无明显差异; SiO₂薄膜在K9和YAG基底上呈现不同的划痕破坏模式, 并且YAG晶体上薄膜的粘附失效临界附着力远远小于SiO₂薄膜与K9基底的附着力。本文从薄膜的结构和弹性模量两方面分析解释了不同基底上薄膜的力学行为。     

PVD grown SnS thin films onto different substrate surfaces

Recent interests focus on tin mono sulphide as a potential candidate for an absorber layer in heterojunction solar cells. In the present investigation, SnS thin films have been deposited onto different substrates such as glass, ITO and Mo-coated glass substrate by thermal evaporation method. The compositional, microstructural and photoelectrochemical properties of the SnS films were analyzed depending upon the chemical nature of the substrates used. The SnS layers were polycrystalline with Herzbergite orthorhombic structure on all three substrates and had nearly stoichiometric elemental composition with a Sn/S ratio of ~1.01. The films grown on ITO and Mo-coated glass substrates exhibit (040) as preferred orientation whereas the films deposited on glass showed (111) plane as predominant. The layers were densely packed and well adherent to the substrate surface. The Raman spectra showed bands at 64, 163, 189 and 219 cm^?1, which corresponds to the single phase (SnS) composition of films. p-type conductivity of all the deposited films were determined by the photoresponse studies. The highest photoresponse for the films on the ITO substrate indicates their appropriateness for the solar cell application.     

Mn掺杂Ga_2O_3薄膜的结构及光吸收性能研究

采用磁控溅射法在Si(111)和玻璃衬底上制备出不同Mn掺杂含量的Ga2O3薄膜,使用扫描电子显微镜、电子能谱仪、X射线衍射仪、紫外-可见分光光度计等对Mn掺杂Ga2O3薄膜的表面形貌、结晶特性和光吸收性能进行了研究.结果表明,适量掺杂Mn可抑制薄膜的晶格膨胀,促进Ga2O3薄膜晶粒的定向生长,得到尺寸分布较均匀的多面体晶粒.Mn掺杂使Ga2O3价带项向带隙延伸,光学带隙变窄,吸收边红移,近紫外区吸收增强.     

瞬时蒸发法制备Bi薄膜的微观结构及电输运性能

用瞬时蒸发法在加热到453K的玻璃基体上沉积出了厚度在40-160nm的多晶Bi纳米薄膜。用X射线衍射(XRD)、场发射扫描电子显微术(FE-SEM)分析了薄膜的相结构和表面形貌。在300-350K研究了薄膜厚度与电阻率的关系,随着薄膜厚度增加,电阻率并不是单调减小;随着温度增加,电阻率减小。温度在300K时,Bi薄膜的电阻率在0.36-0.46mΩ·cm之间变化。随着薄膜厚度的增加,Seebeck系数增加。电子浓度、迁移率与薄膜厚度的关系表明薄膜的电输运性能随薄膜厚度的变化而波动。     

ZnxMg1-xS多晶薄膜的制备及其特性研究

采用真空蒸镀技术,在普通石英玻璃衬底上成功制备出固溶体ZnxMg1-xS多晶薄膜.用X射线能量色散谱仪、原子力显微镜、X射线衍射仪、紫外-可见分光光度计等对薄膜晶体成分、表面形貌、结构和光学性质做了分析.结果表明当x＝0.9时,固溶体ZnxMg1-xS晶体形貌生长和结晶性良好,为闪锌矿结构;由于镁成分的掺入,ZnxMg1-xS薄膜的(111)峰位相对于ZnS的(111)峰位向大角度方向移动0.14°;光学吸收边相对于ZnS产生了明显的蓝移,其禁带宽度增加0.19 eV,显示了作为短波光电器件材料和紫外探测材料的应用潜力.     

Al/Al2O3多层膜的研究

用真空蒸镀及自然氧化方法在玻璃基底上制备纳米量级的4、5、6、7对层的Al／Al2O3多层膜。采用称重法测定薄膜的厚度；在常温和低温下使用三点法测定多层膜的电特性；用扫描电镜（sEM）观察薄膜的表面和截面的形貌及成分。结果表明：制备的是纳米量级非晶态的Al／Al2O3多层膜，在常温和低温（77K）下均具有类似负阻的特性。     

XRD and SEM studies of reactively deposited tin oxide thin films

Stoichiometric polycrystalline tin oxide thin films were deposited by the reactive evaporation of tin and the SnO₂ formation was found to be strongly dependent on the deposition parameters. The preferred orientation of the SnO₂ films deposited on different substrates was varying due to the dislocation defects arising during the thin film formation. The X-ray diffraction (XRD) studies identified a tetragonal structure while the scanning electron microscopic (SEM) studies revealed a polycrystalline surface for the SnO₂ films reactively deposited.     

Preparation of AlN thin films by nitridation of Al-coated Si substrate

AlN thin films have been grown on Al-coated Si(100) and Si(111) substrates by using nitridation in high-purity nitrogen ambient, where the Al layer was previously deposited on Si by ultra-high vacuum (UHV) electron beam evaporation. The temperature of nitridation was found to play an important role in the formation of AlN films. XRD results showed AlN films formed by nitridation at 1000°C for 30 min exhibited good crystallinity with the preferred orientation of (002) for both Si(111) and Si(100) cases. Other analysis techniques, like Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy have been used to evidence the formation and purity of the AlN films. Scanning electron microscope observations of the films revealed a closely-packed granular texture.