衬底对沉积碳纳米管薄膜的影响

利用微波等离子体化学气相沉积(MPCVD)方法,分别在不锈钢衬底上和刻线的镍膜上直接沉积了碳纳米管膜。通过SEM、拉曼光谱和XRD表征,讨论了不同衬底对碳纳米管膜生长的影响。结果表明:在一定条件下,可在镍膜上沉积垂直于衬底的高度取向的碳纳米管,但在不锈钢衬底上却长出取向无序的碳纳米管膜,这说明衬底对碳纳米管的取向生长起着关键作用。     

Improvement of M-plane GaN thin film grown on pre-annealing β-LiGaO2 (100) substrate

In this paper, we report the growth of M-plane GaN thin films on LiGaO₂ (100) substrates pre-annealed in vacuum and in air ambient. The surface of M-plane GaN film grown on the LiGaO₂ (100) substrate pre-annealed in air ambient was significantly improved. X-ray diffraction data showed that the M-plane GaN thin film grown on the LiGaO₂ (100) substrate pre-annealed in air ambient has better crystal quality than that grown on the LiGaO₂ (100) substrate pre-annealed in vacuum. In addition, the strain generated between GaN thin film and LiGaO₂ substrate was relaxed when the GaN thin film grew on the LiGaO₂ substrate pre-annealed in air ambient. It revealed that the thermal annealing LiGaO₂ substrate in air ambient can suppress the formation of lithium-rich surface effectively, and then one can grow a high quality M-plane GaN thin film on the LiGaO₂ substrate.     

无位错Te-GaSb(100)单晶抛光衬底的晶格完整性

采用液封直拉(LEC)法批量生长的直径2英寸(1英寸=2.54 cm)n型Te-GaSb(100)单晶的位错腐蚀坑密度(EPD)通常低于300 cm^-2,达到无位错水平。本文利用X射线摇摆曲线以及倒易空间图(RSM)对这种GaSb单晶抛光衬底的晶格完整性和亚表面损伤情况进行了分析表征,结果表明经过工艺条件优化的化学机械抛光处理,GaSb单晶衬底表面达到原子级光滑,不存在亚表面损伤层。利用分子束外延在这种衬底上可稳定生长出高质量的Ⅱ类超晶格外延材料并呈现出优异的红外探测性能。在此基础上,对CaSb衬底材料的物性、生长制备和衬底加工条件之间的内在关系进行了综合分析。     

Systematic study of various stages during the growth process of diamond-like carbon film by atomic force microscopy

The diamond like carbon (DLC) films have been grown by radio frequency plasma enhanced chemical vapor deposition (RF-PECVD) in methane-argon plasma. In PECVD, the plasma sheath potential drop arising due to argon plasma was utilized to grow the DLC film on silicon (100) substrate at low temperature without using any external negative bias voltage. The growth process of the DLC film has been studied completely starting from nucleation to continuous film by atomic force microscopy. It was seen that the DLC film nucleates around surface defects on the substrate and that the film growth occurs by both adatom deposition and coalescence between nucleated islands. Raman spectrum confirms that the DLC film nucleates excessively in sp² hybridized state and that during the growth process the fraction of sp³ CH_x (x = 1 − 3) increases which leads to the amorphous nature of the film. Long range uniformity of the film was identified using scanning electron microscope.     

衬底温度对共蒸发制备GaSb多晶薄膜性质的影响

采用共蒸发的方法在玻璃衬底上制备出GaSb多晶薄膜材料.研究了薄膜生长速率与衬底温度、Ga源温度和Sb源温度的关系.通过XRD、UV-Vis、Hall效应和AFM等测试方法,研究了衬底温度对于GaSb薄膜的结构特性、光电性质以及表面形貌的影响.GaSb多晶薄膜具有(111)择优取向,薄膜的吸收系数达到105 cm-1,晶粒尺寸随衬底温度升高逐渐增大;衬底温度为540℃时,薄膜的迁移率达到127 cm2/V·s,空穴浓度为3×1017 cm-3.GaSb薄膜的表面粗糙度随温度增加而增加.     

Gas barrier characteristics of a polysilazane film formed on an ITO-coated PET substrate

With the aim of developing a high-performance gas barrier material, a polysilazane film was applied to an indium tin oxide (ITO)-coated organic PET substrate (i.e., the ITO and polysilazane films were formed sequentially on the PET substrate), and its properties were evaluated. The resulting material exhibits favorable gas barrier characteristics (oxygen permeability 0.02 cc/m² day, water vapor permeability 0.15 g/m² day) and performs well as a gas barrier. By controlling the atmosphere during heat treatment when forming the polysilazane film, it is possible to form a highly transparent film with good gas barrier performance. Since this material also conducts electricity due to the presence of the ITO film, it can be used to implement various advanced functions.     

Dynamic process of crystallization of Sb2Se3 from Sb50Se50 amorphous film

Dynamics of crystallization of amorphous antimony-selenium film deposited on carbon substrate have been studied by the high-resolution transmission electron microscopy. The amorphous film was suddenly crystallized at 200°C by heating in vacuum. By the electron beam irradiation crystallization occurred at the focused electron beam region in the amorphous film. The growth process of crystallization by electron beam irradiation was recorded on a video image at the atomic resolution mode. The growth front of crystallization showed nano-concave and -convex shapes. The recrystallization with the different orientation at the first grown crystal have been found, and discussed as the influence of remaining antimony crystallites at the first crystallized film region.     

MBE growth of PbSe thin film with a 9×10 cm etch-pits density on patterned (1 1 1)-oriented Si substrate

PbSe thin film was grown on a patterned Si substrate with (1 1 1)-orientation by molecular-beam epitaxy (MBE). On the mesa, a low dislocation density of 9×10⁵ cm⁻² was confirmed by the etch-pits density (EPD) wet-etching technique. The photoluminescence (PL) intensity at room temperature from the low dislocation PbSe film was much higher than that from the PbSe film grown on the planar area, which further indicated the high-quality of PbSe thin film grown on patterned Si substrate.     

Measuring the Electrical Conductivity of Carbon Nanotubes Grown on Sodalime Glass Substrates using Cu as Catalyst

We have studied the electrical resistance of carbon nanotubes (CNTs) grown on sodalime glass using Cu as catalyst at 580°C temperature. The conductivity was measured at room temperature using four point probe technique. The Cu catalyst was coated on glass substrate by using dc magnetron sputtering system and etched by hydrogen (H₂) gas in order to form nanometer sized catalytic particles. Mixture of C₂H₂/H₂/Ar (20:80:100 standard centimeter cubic per minutes) gases were heated at 580°C for growth of CNTs on a glass substrate by using Thermal Chemical Vapor Deposition (TCVD). The temperature dependence of sheet resistance and current-voltage characteristics of the film were measured by a four point probes method. The morphology of the catalyst surface was probed by Atomic Force Microscopy (AFM), and the growth behavior of CNTs was investigated by scanning electron microscopy (SEM).     

Temperature gradient induced phase transitions and morphological changes in diamond thin film

The diamond films were deposited onto a wurtzite gallium nitride (GaN) thin film substrate using hot-filament chemical vapor deposition (HFCVD). During the film deposition a lateral temperature gradient was imposed across the substrate by inclining the substrate. As grown films predominantly showed the hexagonal phase, when no inclination was applied to the substrate. Tilting the substrate with respect to the heating filament by 6° imposed a lateral temperature gradient across the substrate, which induced the formation of a cubic diamond phase. Diamond grains were predominantly oriented in the (100) direction. However, a further increase in the substrate tilt angle to 12°, resulted in grains oriented in the (111) direction. The growth rate and hence the morphology of diamond grains varied along the inclined substrate. The present study focuses on the measurements of dominant phase formation and crystal orientation with varying substrate inclination using orientation-imaging microscopy (OIM). This technique enables direct examination of individual diamond grains and their crystallographic orientation.     

GaSb薄膜生长的RHEED研究

采用分子束外延技术,在GaAs衬底上生长GaSb薄膜时,利用反射式高能电子衍射仪(RHEED)对衬底表面清洁状况、外延层厚度等进行在线监控.通过RHEED讨论低温缓冲层对GaSb薄膜表面结构和生长机制的作用,可以估算衬底温度,并能计算出薄膜的生长速率.实验测量GaSb的生长周期为1.96s,每秒沉积0.51单分子层.低温缓冲层提高了在GaAs衬底上外延GaSb薄膜的生长质量.     

Structural and electrical properties of GaSb, AlGaSb and their heterostructures grown on GaAs by metalorganic chemical vapor deposition

A systematic study of structural and electrical properties of GaSb and AlGaSb grown on GaAs by metalorganic chemical vapor deposition is reported. In general, the results obtained from surface morphologies, X-ray linewidths and Hall properties are consistent with each other and indicate that the optimal growth conditions for GaSb are at 525°C around V/III = 1. A highest hole mobility of 652 cm²/V · s at RT (3208 cm²/V · s at 77 K) and a lowest concentration of 2.8 × 10¹⁶ cm⁻³ (1.2 × 10¹⁵ cm⁻³ at 77 K) were obtained for GaSb grown under this optimal condition. Compared to the GaSb growth, a smaller V/III ratio is needed for the AlGaSb growth to protect the surface morphology. When Al was incorporated into GaSb growth, mobility decreased and carrier concentration increased sharply. The AlGaSb grown at 600°C had a background concentration about one order of magnitude lower than the AlGaSb grown at 680°C. Room-temperature current-voltage characteristics of GaSb/Al_xGa_{1 − x}Sb/GaSb show a rectifying feature when Al composition x is higher than 0.3, suggesting a valence-band discontinuity at the AlGaSb/GaSb interface. A leakage current much higher than the value predicted by the thermionic emission theory is observed at 77 K, presumably due to a large number of dislocations generated by the huge lattice mismatch between GaSb and GaAs.     

金刚石薄膜在硬质合金基体上的生长及附着强度研究

硬质合金是制作金刚石薄膜涂层刀具的重要基体材料,金刚石薄膜在硬质合金基体上的成核、生长及界面特征直接影响其附着强度.本文通过扫描电镜、X射线衍射分析、X射线光电子谱(XPS)及断续切削实验,研究了硬质合金基体含Co量对金刚石薄膜成核、生长及附着强度的影响.研究结果表明,经酸洗处理后,硬质合金基体含Co量对金刚石薄膜成核、生长没有太大影响.但对其附着强度有很大影响.含Co量越高,附着强度越低.酸腐蚀去Co处理后基体表面变得疏松、不连续非金刚石碳界面的存在及热膨胀系数较大是含Co量较高时,附着强度下降的主要原因.     

Influence of surface topography on the multilayer film formation

The relationship between the topography of substrates and multilayer films deposited on these substrates (which are used in ring laser gyroscopes) has been investigated. The surfaces were studied by atomic-force microscopy. The statistical properties of the surface topography are analyzed within the approach based on a comparative analysis of the power spectral density functions of roughness calculated for the substrate and film. The degree of correlation between the substrate nanotopography and multilayer film is determined, and the influence of the substrate roughness on the optical characteristics of the deposited mirrors is established.     

Influence of substrate and film thickness on structural,optical and electrical properties of ZnO thin films

Transparent Zinc Oxide (ZnO) thin films have been grown on Si (100) and Sapphire (0001) substrates by RF magnetron sputtering for different growth time intervals (10, 30 and 60 min) to study the substrate and thickness effects. All the films have been grown at a substrate temperature of 450 °C. It has been found that the average growth rate on Si (100) substrate (8.6 nm/min) is higher than that on Sapphire (0001) substrate (2.6 nm/min) in an identical growth condition which clearly shows the virtual role of substrates. The lower growth rate on Sapphire (0001) suggests that the increasingly ordered and uniform growth due to less lattice mismatch. The grown films have been characterized by X‐ray diffraction (XRD), Reflectance, Photoluminescence (PL) and Hall measurements. The XRD result (FWHM) reveals that for lower growth time, the films grown on Si (100) is better than on Sapphire (0001). Conversely, for higher growth time, the films grown on Sapphire (0001) is better than on Si (100). The variation of strain behavior due to thickness on both substrates has been justified by UV‐Vis reflectance, photoluminescence and Hall effect measurements. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

[100]定向织构生长金刚石薄膜的红外光学性能研究

采用微波等离子增强化学气相沉积法在(100)镜面抛光的硅片衬底上实现了金刚石薄片[100]定向织构生长.并用扫描电子显微镜、拉曼散射和傅立叶红外光谱仪分析测试了不同工艺得到的金刚石薄片的表面形貌、组成结构和红外性能.结果表明:负偏压辅助定向成核和氢的等离子刻蚀不仅促进了金刚石薄膜的定向织构生长,而且还能刻蚀成核期的非金刚石成分.从而提高了金刚石薄片的红外光透过特性.     

Thickness and substrate orientation dependence of ferromagnetism in Mn doped ZnO thin films

The effect of film thickness and substrate orientation on ferromagnetism in Mn doped ZnO thin films have been studied. The Mn doped ZnO films of different thickness (15, 35 and 105 nm) have been grown on both Si (100) and Si (111) substrates. The structural, electrical, optical, elemental and magnetic properties of the films have been investigated by X‐ray diffraction (XRD), Hall Effect measurements, photoluminescence (PL), energy dispersive spectroscopy (EDS) and vibrating sample magnetometer (VSM), respectively. It is found that all the properties are strongly influenced by the film thickness and substrate orientation. The XRD analysis confirmed that the formation of high quality monophasic hexagonal wurtzite structure for all the grown films. The room temperature VSM measurements showed that the films of lower thickness have better ferromagnetism than that of the thicker films grown on both the substrates. Among the lower thickness films, the film grown on Si (111) substrate has higher saturation magnetization (291×10^‐5 emu cm^‐3) due to high density of the defects. The observed ferromagnetism has been well justified by XRD, Hall measurements and PL. The presence of Mn atoms in the film has been confirmed by EDS. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Influence of plasma power and substrate temperature on structure of nanocrystalline germanium carbon thin films by VHF plasma CVD

The influence of plasma power and substrate temperature on the structure of nanocrystalline germanium carbon thin films was investigated. Films were deposited by the very high frequency plasma chemical vapor deposition technique using hydrogen diluted monomethylgermane (MMG). Plasma power strongly affected the decomposition of hydrogen and MMG. Crystalline volume fraction and bonding states of the atoms in the films depends on plasma power and substrate temperature. FT-IR measurements also revealed that Ge–H_n and CH_n bonds are sensitive to these factors.     

加氮对直流电弧等离子体喷射金刚石膜生长、形貌和质量的影响

利用直流等离子体喷射化学气相沉积法制备掺氮的金刚石厚膜.本文研究了在甲烷/氩气/氢气中加入氮气对金刚石膜生长、形貌和质量的影响.反应气体的比例由质量流量计控制,在固定氢气(5000sccm)、氩气(3000sccm)、甲烷(100sccm)流量的情况下改变氮气的流量,即反应气体中氮原子和碳原子的变化比例(N/ C比)范围是从0.06到0.68.同时金刚石膜在固定的腔体压力(4kPa)和衬底温度(800℃)下生长.金刚石膜用扫描电镜(SEM)、拉曼谱和X射线衍射表征.结果表明,氮气在反应气体中的大量加入对直流等离子体喷射制备金刚石膜的形貌、生长速率、晶体取向、成核密度等有非常显著的影响.     

Investigation of 3C-SiC growth on Si(111) by vapor–liquid–solid transport using a SiGe liquid phase

The crystal growth of 3C-SiC onto silicon substrate by Vapor–Liquid–Solid (VLS) transport, where a SiGe liquid phase is fed with propane, has been investigated. Three sample configurations were used. In a preliminary approach, the VLS growth of SiC was conducted directly onto Si substrate using a Ge film as liquid catalyst. It led to the growth of a thick continuous SiC polycrystalline layer which was floating over a SiGe alloy located between the silicon substrate and the topping SiC layer. In the second configuration, a thin seeding layer of 3C-SiC grown by chemical vapor deposition (CVD) was used and the VLS growth was localized using a SiO₂ mask. The liquid phase was a CVD deposited SiGe alloy. The growth of a few hundred nanometers thick 3C-SiC epitaxial layer was demonstrated but the process was apparently affected by the presence of the oxide which was dramatically etched at the end. In the last configuration, the silicon substrate was patterned down to 10 μm and a thin seeding layer of 3C-SiC was grown by CVD onto this patterned substrate. The liquid phase was again a CVD deposited SiGe alloy. In this last configuration, the presence of epitaxial SiC was evidenced but it grew as trapezoidal islands instead of an uniform layer.