Observation of defects and growth orientations of YBa2Cu3Ox thin films with YSZ buffer layers on Si

We have investigated defects and in-plate orientations of YBa₂Cu₃O_x thin films prepared by pulsed laser deposition (PLD) with YSZ as a buffer layer. The films showed c-axis oriented growth with the transition temperature T_co up to 87 K. Several types of defects including thermally induced cracks, grain boundaries and outgrowths were observed by scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). The grain boundary provided a favorable path for crack propagation. The outgrowths nucleated on the YSZ surface grew with stoichiometric composition. According to X-ray diffraction (XRD) and HRTEM studies the YSZ buffer layer grew with the orientation relationship, YSZ110//Si110 and YSZ(001)//Si(001) up to the YBCO/YSZ interface. The superconducting YBCO films on top grew mainly with YBCO100//Si110 and YBCO(001)//Si(001), with some minor portions of YBCO110//Si110 and YBCO(001)//Si(001).     

Structural and dc conduction studies on PbTe thin films

Lead Telluride (PbTe) films of different thickness were prepared onto precleaned glass substrates under the pressure of 2?×?10^?5 Torr by thermal evaporation. X-ray diffraction technique, scanning electron microscopy, and current–voltage characteristics were used to characterize the films. The structural analysis of the films was carried using X-ray diffractometer. The surface morphology was analyzed by using scanning electron microscope. The dc electrical conduction mechanism in vacuum-evaporated Al/PbTe/Al thin film sandwich system in the thickness range 500–5,000 Å at different temperature (303–483 K) was found to be a modified Poole–Frenkel type. The results of variation of activation energy with applied voltage and thickness are discussed.     

Polycrystalline silicon films prepared by metal-induced crystallisation using pre- and post-deposited aluminium on amorphous silicon

We report on the successful fabrication of polycrystalline silicon films by aluminium-induced crystallisation (AIC) of Radio frequency (rf) plasma-enhanced chemical vapour deposited (PECVD) a-Si films. The effects of annealing at different temperatures (300 and 400°C), below the eutectic temperature of the Si–Al binary system, on the crystallisation process have been studied. This work emphasises the important role of the position of the Al layer with respect to the Si layer on the crystallisation process. The properties of the crystallised films were characterised using X-ray diffraction, Raman spectroscopy, ellipsometry, field-emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). With an increase in the annealing temperature, it was found that the degree of crystallisation of annealed a-Si/Al and Al/a-Si films increased. The results showed that the arrangement where the Al was on top of the a-Si had a more prominent effect on crystallisation enhancement than when Al was below the a-Si. The interfacial layer between the Al and a-Si film is crucial because it influences the layer-exchange process during annealing. The oxide layer formed between the Al and the a-Si layers greatly retards the crystallisation process in the case of the Al/Si arrangement. Our investigations suggest that polycrystalline Si films formed by AIC can be used as a seed layer in solar cell fabrication.     

The study of structure and optoelectronic properties of ZnS and ZnO films on porous silicon substrates

ZnS and ZnO films were prepared on porous silicon (PS) substrates with the same porosity by pulsed laser deposition (PLD), and the structural, optical and electrical properties of ZnS and ZnO films on PS were investigated at room temperature by X-ray diffraction (XRD), scanning electron microscope (SEM), optical absorption measurement, photoluminescence (PL) and I–V characteristic studies. The prepared ZnS was obtained in the cubic phase along β-ZnS (1 1 1) orientation which showed a perfect match with the earlier report while ZnO films were obtained in c-axis orientation. There appeared some cracks in the surface of ZnS and ZnO films due to the roughness of PS substrates. Luminescence studies of ZnS/PS and ZnO/PS composites indicated room temperature emission in a broad, intense, visible photoluminescence band, which cover the blue emission to red emission, exhibiting intensively white light emission. Based on the I–V characteristic, ZnS/PS heterojunction exhibited the rectifying junction behavior, while the I–V characteristic of ZnO/PS heterostructure was different from that of the common diode, whose reverse current was not saturated.     

Fractal microstructures of light-emitting porous silicon films

By means of scanning electron microscopy and computer simulation, we have investigated the microstructures of a 23-μm-thick porous silicon (PS) film and a 6-μm-thick PS film. The two films give off strong visible emissions when excited by the 254 nm light. For the 23-μm-thick PS film, both of its cross-sectional and top-surface morphologies exhibit self-similarity whose small-scale and large-scale microstructures resemble one another. For the 6-μm-thick PS film, self-similar cracks are developed on its top surface. Our results have demonstrated that the microstructures of PS films exhibit the characteristics of fractals. With box counting method, the fractal dimensions of the PS films are calculated to be about 2.3-2.6. Based on the model of diffusion-limited aggregation, the fractal growth processes have been simulated for the PS films.     

负偏压热灯丝CVD金刚石膜核化和早期生长的研究

利用扫描电子显微镜、Raman谱和X射线光电子能谱，研究了Si衬底上热灯丝CVD金刚石膜的核化和早期生长.在-300V和100mA条件下预处理15min，镜面抛光的Si(100)表面上金刚石核密度超过了10⁹cm^-2，但是核的分布极不均匀且可分为三个区域：A区，边缘处以锥体为主；B区，位于边和中心之间过渡区是纳米金刚石；C区，中心处有SiC层.无偏压下生长4h后，A区形成许多大而弧立的金刚石颗粒，B区成为织构金刚石膜，而C区变为含有大量缺陷的连续金刚石膜.衬底负 关键词：     

Fabrication and tribological properties of super-hydrophobic surfaces based on porous silicon

In the present work, super-hydrophobic surfaces based on porous silicon (PS) were constructed by the self-assembled molecular films and their tribological properties were investigated. A simple chemical etching approach was developed to fabricate PS with the certain rough microstructure surface, which can be observed by the environmental scanning electron microscopy (ESEM). The hydrocarbon and fluorocarbon alkylsilane molecular films were self-assembled on PS, which was confirmed by the X-ray photoelectron spectroscopy (XPS) measurement. In contrast to PS, the alkylsilane molecular films modified PS (mPS) were super-hydrophobic since the apparent water contact angle (CA) exceeded 160°. The tribological properties of PS and the mPS were investigated by a ball-on-disk tribometer during the processes of different sliding velocities and normal loads. The experimental results showed that the alkylsilane molecular films could decrease the friction coefficient. Due to the difference of chain structure and functional groups, the fluorinated alkylsilane films are better candidates for improving the hydrophobicity and lubricating characteristics of PS comparing to the non-fluorinated ones. The carbon chain length of alkylsilane molecules self-assembling on the Si or PS substrates could have little effects on the hydrophobic properties and the tribology performances.     

Si基Sc膜的制备及结构分析

采用电子束镀膜方法在Si基底上制备了Sc膜,利用XRD,SEM分析了不同镀膜工艺条件下制备的Sc膜的形貌和结构。结果表明:基底温度在350～550 ℃时,薄膜主要由单质Sc组成,而且随着基底温度的升高,膜的颗粒尺寸增大,膜也变得更加致密;基底温度提高至650 ℃时,膜全部由ScSi化合物组成,膜变成颗粒状结构。沉积速率对低温时Sc膜的形貌与结构的影响不明显,颗粒尺寸随沉积速率的增大而增大,但物相结构基本没有发生变化;而在高温650 ℃时,沉积速率对膜的形貌与结构产生了很大的影响,随着沉积速率的增大,膜表面出现了大量微裂纹,而且较低的沉积速率有利于获得衍射峰单一的膜,增大沉积速率将会导致衍射峰数量明显增加。     

Morphology and properties of ZnO films obtained by repeated spin coating on porous silicon substrates

Layers of porous silicon (PS), multilayered ZnO films, and heterostructures based on them are obtained. The surface morphology, chemical and phase composition of the PS layers and ZnO films, and the transverse cleavage of ZnO–PS nanocomposite, are investigated via energy-dispersive X-ray spectral analysis (EDX), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The current–voltage characteristics of Al/Ag/p-Si(100)/PS/ZnO/Ag/Al and Al/Ag/p-Si(100)/PS/ZnO/SiC/Ag/Al heterostructures are studied.     

Synthesis of molybdenum silicide by both ion implantation and ion beam assisted deposition

Two groups of Mo/Si films were deposited on surface of Si(1 0 0) crystal. The first group of the samples was prepared by both ion beam assisted deposition (IBAD) and metal vapor vacuum arc (MEVVA) ion implantation technologies under temperatures from 200 to 400 °C. The deposited species of IBAD were Mo and Si, and different sputtering Ar ion densities were selected. The mixed Mo/Si films were implanted by Mo ion with energy of 94 keV, and fluence of Mo ion was 5 × 10¹⁶ ions/cm². The second group of the samples was prepared only by IBAD under the same test temperature range. The Mo/Si samples were analyzed by X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), sheet resistance, nanohardness, and modulus of the Mo/Si films were also measured. For the Mo/Si films implanted with Mo ion, XRD results indicate that phase of the Mo/Si films prepared at 400 and 300 °C was pure MoSi₂. Sheet resistance of the Mo/Si films implanted with Mo ion was less than that of the Mo/Si films prepared without ion implantation. Nanohardness and modulus of the Mo/Si films were obviously affected by test parameters.     

矫顽力可调的多孔硅基Fe膜

采用电化学腐蚀法制备了不同多孔度的多孔硅(PS),再通过磁控溅射法在该PS衬底上沉积了一定厚度的Fe膜;并对样品进行了X射线衍射的结构分析、扫描隧道显微技术的表面形貌观察和磁光克尔效应的测量.发现在同一Fe膜厚度下，相对于参考样品硅上的Fe膜，多孔硅上Fe膜的矫顽力更大;同时观察到多孔硅基Fe膜随着PS多孔度的增加，矫顽力相应变大;而对于多孔度相同的多孔硅基样品,随着Fe膜厚度的增加矫顽力却逐步减小.得出了多孔硅特有的海绵状疏松结构能有效调节Fe膜矫顽力大小的结论. 关键词： 多孔硅 海绵状结构 Fe薄膜 矫顽力     

Growth Kinetics of Silicon Carbide Film Prepared by HeatingPolystyrene/Si(111)

在不同的温度下热处理用sol-gel法制的PS/Si(111)叠层凝胶膜制备出了SiC薄膜．用XRD、SEM、XPS、FTIR等分析方法研究了SiC薄膜的结构、组成和表面形貌等．根据FTIR光谱计算了不同温度下得到的SiC薄膜的厚度,并研究了PS/Si(111)热解法生长SiC薄膜的生长动力学．结果表明,随着生长温度的增加,SiC薄膜生长速率变化趋势为：1200～1250 oC生长速率增加缓慢是2D生长机制,1250～1270 oC生长速率快速增加是3D生长机制,1270～1300 oC生长速率为负增长是由于SiC薄膜生长与Si和C原子的挥发共同作用所致．由速率变化求得各段表观生长激活能分别是122.5、522.5、-127.5 J/mol．     

The 60° or 180° twinned Bi-doped PbTe film studied by EBSD

The Bi-doped PbTe film was grown on Si(1 1 1) substrate by using hot wall epitaxy (HWE) technique. The film was characterized by means of scanning electron microscopy, micro-area X-ray diffraction and electron backscatter diffraction (EBSD). The results indicate that the film is dominated by 〈1 1 1〉 orientation. The film consists of two twinned domains, rotated 60° or 180° around the normal to the film surface. It is speculated that the twinned PbTe film results from the deviated triangular grains. The ratio between the grains with two different orientations will decrease with the increase of the film thickness.     

Growth and structural characterization of semiconducting Ru2Si3

Recent band structure calculations indicate that ruthenium silicide (Ru₂Si₃) is semiconducting with a direct band gap. Electrical measurements lead to a band gap around 0.8 eV which is technologically important for fiber communications. This makes Ru₂Si₃ a promising candidate for silicon based optical devices, namely LEDs. We present first results on the epitaxial growth of ruthenium silicide films on Si(1 0 0) and Si(1 1 1) fabricated by the template method, a special molecular beam epitaxy technique. Orientational relationships on Si(1 1 1) have been determined. We characterized the films by Rutherford Backscattering and Channeling, X-ray diffraction and transmission electron microscopy.     

Effects of rapid thermal annealing on the morphology and optical properity of ultrathin InSb film deposited on SiO2/Si substrate

Ultrathin InSb thin films on SiO₂/Si substrates are prepared by radio frequency (RF) magnetron sputtering and rapid thermal annealing (RTA) at 300, 400, and 500℃, respectively. X-ray diffraction (XRD) indicates that InSb film treated by RTA at 500℃, which is higher than its melting temperature (about 485℃), shows a monocrystalline-like feature. High-resolution transmission electron microscopy (HRTEM) micrograph shows that melt recrystallization of InSb film on SiO₂/Si(111) substrate is along the (111) planes. The transmittances of InSb films decrease and the optical band gaps redshift from 0.24 eV to 0.19 eV with annealing temperature increasing from 300℃ to 500℃, which is indicated by Fourier transform infrared spectroscopy (FTIR) measurement. The observed changes demonstrate that RAT is a viable technique for improving characteristics of InSb films, especially the melt-recrystallized film treated by RTA at 500℃.     

MgO和Si上NbN超薄薄膜的生长研究

我们在单晶MgO(100)、Si(100)和SiOx/Si基片上成功生长了纳米厚度的超薄NbN薄膜,利用现代分析手段:X射线衍射(XRD)、透射电子显微镜(TEM)、原子力显微镜(AFM)等技术分析研究了所制备的超薄NbN薄膜的微观结构、厚度、表面界面情况等物理特性。研究表明,在MgO(100)基片上获得了外延生长的单晶NbN超薄薄膜,在Si(100)和SiOx/Si基片上获得的是多晶NbN超薄薄膜。厚度均约6nm左右。这些超薄薄膜的超导转变温度分别为:MgO上薄膜是14.46K,Si和SiOx上薄膜分别是8.74K和9.01K.     

织构金刚石薄膜的成核与生长

在加衬底偏压和不加衬底偏压两种情况下，用微波等离子体化学汽相沉积（MWCVD）技术在Ｓｉ（１００）衬底上合成了织构的金刚石薄膜使用扫描电子显微镜（ＳＥＭ）和取向Ｘ射线衍射技术证实了我们得到的样品是织构的金刚石薄膜观察了织构的金刚石薄膜的成核和生长过程，从理论上对金刚石薄膜异质外延的成核和生长机理进行了探讨 关键词：     

Formation of high quality gallium nitride thin films on Ga-diffused Si(1 1 1) substrate

High quality gallium nitride thin films have been successfully grown on the Ga-diffused Si(1 1 1) substrates through ammoniating Ga₂O₃ thin films deposited by r.f. magnetron sputtering. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), atomic force microscope (AFM) and photoluminescence (PL) were used to characterize the synthesized samples. The analyses reveal that the formed films are high quality polycrystalline hexagonal gallium nitride. The as-formed GaN films show a flat surface topography with RMS roughness varied from 29 to 48 Å. The strong near-band-edge-emission peak around 368 nm was observed at room temperature. This is a novel method to fabricate GaN thin films based on the direct reaction between Ga₂O₃ and NH₃ on the Ga-diffused Si(1 1 1) substrates.     

立方氮化硼薄膜的生长特性与粘附性研究

用X射线衍射技术、红外吸收光谱、扫描电子显微镜、X射线光电子能谱对热丝辅助射频等离子体化学汽相沉积法制备的立方氮化硼(c-BN)薄膜的生长特性和粘附性进行了研究.改变生长条件，在Si、不锈钢和Ni衬底上沉积c-BN薄膜，进而研究了c-BN薄膜的质量和生长条件与衬底之间的关系.实验发现，Ni衬底上生长的薄膜c-BN含量较高，且粘附性好.当Si衬底上溅射一层Ni过渡层，再生长c-BN薄膜，薄膜中c-BN含量提高，与Si衬底的粘附性也显著增强. 关键词：     

Low-macroscopic field emission from silicon-incorporated diamond-like carbon film synthesized by dc PECVD

Silicon-incorporated diamond-like carbon (Si-DLC) films were deposited via dc plasma-enhanced chemical vapor deposition (PECVD), on glass and alumina substrates at a substrate temperature 300 °C. The precursor gas used was acetylene and for Si incorporation, tetraethyl orthosilicate dissolved in methanol was used. Si atomic percentage in the films was varied from 0% to 19.3% as measured from energy-dispersive X-ray analysis (EDX). The binding energies of C 1s, Si 2s and Si 2p were determined from X-ray photoelectron spectroscopic studies. We have observed low-macroscopic field electron emission from Si-DLC thin films deposited on glass substrates. The emission properties have been studied for a fixed anode-sample separation of 80 μm for different Si atomic percentages in the films. The turn-on field was also found to vary from 16.19 to 3.61 V/μm for a fixed anode-sample separation of 80 μm with a variation of silicon atomic percentage in the films 0% to 19.3%. The turn-on field and approximate work function are calculated and we have tried to explain the emission mechanism there from. It was found that the turn-on field and effective emission barrier were reduced by Si incorporation than undoped DLC.