Effect of Gas Pressure on Nanocrystalline Diamond Films Prepared by Electron-Assisted Chemical Vapour Deposition

With use of electron-assisted chemical vapour deposition （EACVD） technology, nanocrystalline diamond films are successfully deposited on an α-SiC single phase ceramics substrate by means of reduction of the reactive gas pressure. The structure and surface morphology of the deposited films are characterized by Raman spectroscopy, x-ray diffraction （XRD）, field emission scanning electron microscopy （FE-SEM） and atomic force microscopy （AFM）. The results examined by FE-SEM and AFM show that when the gas pressure was reduced to 0.5- 1 kPa, the surface grain size and surface roughness of the diamond film are decreased greatly to 18-32nm and 34-58nm respectively. The grain sizes estimated from full with at half maximum of （111） XRD peak by the Scherrer formula are 6-28 nm. However, too high secondary nucleation rate may result in pores and defects in the deposited films. Only at suitable gas pressure （1 kPa） to deposit films can we obtain densification and better quality nanocrystalline films.     

Preparation and Characteristics of GaN Films on Freestanding CVD Thick Diamond Films

Prefer-oriented and fine grained polycrystalline GaN films are prepared by plasma enhanced metal organic chemical vapour deposition on nucleation surfaces of freestanding thick diamond films. The characteristics of the GaN films are characterized by x-ray diffraction, reflection high energy electron diffraction and atomic force microscopy. The results indicate that the structure and morphology of the films are strongly dependent on the deposition temperature. The most significant improvements in morphological and structural properties of GaN films are obtained under the proper deposition temperature of 400°C.     

Influences of Annealing on the Opto—electronic Properties of ZnO Films Grown by Plasma—Enhanced MOCVD

ZnO thin films have been grown on C-plane sapphire substrates by plasma-enhanced metal-organic chemical vapour deposition.The samples are then annealed at a higher temperature.The resistivity,concentration of electron,mobility and optically pumped threshold of both as-grown and annealed films are investigated.Furthermore,their structural and optical properties are also examined with x-ray diffraction,emission spectra and optical transmission spectra.The results indicate that the quality of ZnO thin films can be improved by annealing.     

Fabrication and Characterization of Ni Thin Films Using Direct-Current Magnetron Sputtering

Ni films are deposited by using ultra high vacuum dc magnetron sputtering onto silicon substrates at room temperature, and the high-quality and high-density films are prepared. The parameters, such as thickness, density and surface roughness, are obtained by using small-angle x-ray diffraction (XRD) analyses with the Marquardt gradient-expansion algorithm. The deposition rate is calculated and the Ni single layer can be fabricated precisely. Based on the fitting results, we can find that the surface roughness of the Ni films is about 0.7nm, the densities of Ni films are around 97% and the deposition rate is 0.26nm/s. The roughness of the surface is also characterized by using an atomic force microscope (AFM). The changing trend of the surface roughness in the simulation of XRD is in good agreement with the AFM measurement.     

Growth of a-Plane GaN Films on r-Plane Sapphire Substrates by Metalorganic Chemical Vapour Deposition

Nonpolar a-plane CaN films were grown on r-plane sapphire substrates by metalorganic chemical vapour deposition (MOCVD) under various conditions. The surface morphologies of epitaxial films are studied by atomic force microscopy. The pit density and size both decrease with the increasing growth temperature, decreasing growth pressure or V/Ⅲ ratio, while the roughness of the surface increases. Formation mechanisms of the pits in the films are discussed.     

Dielectric Characterization of Free—Standing Diamond Films

The dielectric properties of free-standing diamond films grown by the dc arc-jet plasma method are measured by an impedance analyser in the temperature range of 298-573K and at frequencies between 1000Hz and 1MHz.In the temperature and frequency ranges,the loss tangent can be expressed as a function of temperature and frequency.The loss tangent increases slightly with increasing temperature and frequency,The dielectric properties of the diamond films decrease with the increasing deposited temperature.The structure and quality of diamond films have been analysed by scanning electron microscopy,x-ray diffraction and raman spectroscopy.     

Effect of CO2 Addition on Preparation of Diamond Films by Direct-Current Hot-Cathode Plasma Chemical Vapor Deposition Method

Diamond films are deposited on Mo substrates by dc hot-cathode plasma chemical vapor deposition method using a CH4-H2-CO2 gas mixture. Adjusting the flow of CO2, we study the relevant influence on surface morphology, grain orientation and crystalline quality of films with scanning electron microscopy, x-ray diffraction, Raman spectroscopy, respectively. The results show that grain orientation of the films has a transition with the increasing CO2 addition, from （100） orientation to （110） orientation and then （111） orientation. The crystalline quality is improved but the growth rate is decreased by raising the flow of CO2. The experimental results are also discussed briefly.     

Effect of Different Substrate Temperature on Phosphorus-Doped ZnO Thin Films Prepared by PLD on Sapphire Substrates

Phosphorus-doped ZnO （ZnO：P） thin films are deposited on a c-plane sapphire in oxygen at 350℃, 450℃, 550℃ and 650℃, respectively, by pulsed laser deposition （PLD）, then all the ZnO：P samples are annealed at 650℃ in oxygen with a pressure of 1 × 10^5 Pa. X-ray diffraction measurements indicate that the crystalline quality of the ZnO：P thin films is improved with the increasing substrate temperature from 350℃ to 550℃. With a further increase of the deposition temperature, the crystalline quality of the ZnO：P sample is degraded. The measurements of low-temperature photoluminescence spectra demonstrate that the samples deposited at the substrate temperatures of 350℃ and 450℃ show a strong acceptor-bound exciton （A^0X） emission. The electrical properties of ZnO：P films strongly depend on the deposition temperature. The ZnO：P samples deposited at 350℃ and 450℃ exhibit p-type conductivity. The p-type ZnO：P film deposited at 450℃ shows a resistivity of 1.846Ω·cm and a relatively high hole concentration of 5.100 × 10^17 cm^-3 at room temperature.     

Epitaxial Properties of Co-Doped ZnO Thin Films Grown by Plasma Assisted Molecular Beam Epitaxy

High quality Co-doped ZnO thin films are grown on single crystalline Al2O3（0001） and ZnO（0001） substrates by oxygen plasma assisted molecular beam epitaxy at a relatively lower substrate temperature of 450℃. The epitaxial conditions are examined with in-situ reflection high energy electron diffraction （RHEED） and ex-situ high resolution x-ray diffraction （HRXRD）. The epitaxial thin films are single crystal at film thickness smaller than 500nm and nominal concentration of Co dopant up to 20%. It is indicated that the Co cation is incorporated into the ZnO matrix as Co^2＋ substituting Zn^2＋ ions. Atomic force microscopy shows smooth surfaces with rms roughness of 1.9 nm. Room-temperature magnetization measurements reveal that the Co-doped ZnO thin films are ferromagnetic with Curie temperatures Tc above room temperature.     

Optical properties and microstructure of Ta_2O_5 thin films prepared by oblique angle deposition

Tantalum pentoxide thin films are prepared by oblique angle electron beam evaporation. The influence of flux angle on the surface morphology and microstructure is investigated by scanning electron microscopy （SEM）. The Ta2O5 thin films are anisotropic with highly orientated nanostructure of slanted columns. The porous microstructure of the as-deposited films results in the decrease of effective refractive index and packing density with increasing deposition angle. The anisotropic structure results in optical birefringence. The in-plane birefringence increases with the increase of deposition angle and reaches the maximum of 0.055 at the deposition angle of 70°. Anisotropic microstructure and critical packing density are the two key factors to influence the in-plane birefringence.     

Durability of Ultra-Thin Silver Films and Silver-Gold Alloy Films under UV Irradiation

Silver films(Ag) and silver-gold films(Ag-Au) with thickness ~15nm are coated on Bk7 glasses through thermal evaporation.After doping gold of 5.2%,the grain size of the Ag film reduces from 13.6nm to 9.1nm,also the surface roughness decreases from 1.45 nm to 0.94 nm.A UV lamp is used as the irradiation light source to accelerate the corrosion process in the atmosphere.After 17 h irradiation,the pure silver film surface turns dark,and the transmittances reduce from 350 nm to 500 nm,while the Ag-Au film degrades much less,almost negligibly after UV radiation.Additional x-ray photoelectron spectroscopy and atomic force micrographs data are provided to show atomic content of Sims and their surface morphologies.It is suggested that small grain size and high packing density of alloy film prevent reaction of silver with oxygen in the atmosphere,which leads to high stability of the Ag-Au Elm.     

氟掺杂的氧化锌薄膜的结构和光学特性

通过热氧化氟化锌(ZnF2)薄膜的方法制备出氟掺杂的多晶ZnO薄膜,ZnF2薄膜是利用电子束蒸发方法沉积在Si(100)衬底得到的。利用X射线衍射和X射线电子能谱研究了ZnF2薄膜向ZnO的转变过程。实验结果表明,在400℃退火30min的条件下能够获得六方纤锌矿结构的ZnO：F薄膜。对ZnO：F薄膜的室温光致发光谱可以观察到位于379nm、半峰全宽为73meV的紫外发射峰,而相应于缺陷的深能级发射则完全猝灭。表明ZnO中残留的F能够有效地增强激子的发光,同时使缺陷发光强度明显降低。对F掺杂对ZnO的发光性能的影响进行了讨论。     

超分子有机薄膜

利用超分子有机薄膜技术能制成新的传感分子电子器件、光学器件和生物分子器件等，受到跨学科高技术研究领域的重视。本文描述了超分子有机薄膜的制备方法以及在各应用领域的研究状况。重点介绍了我们研究组在近20年工作中，利用LB膜技术，在光电器件、气体传感技术和光学非线性，特别是在生物传感技术方面的研究成果。按照生物体系提供的信息，模拟合成功能分子，建造有组织的分子组装体，以便用来研究依赖于分子排列的生物物理化学效应。     

Fabrication Techniques and Characteristics of Ultra-Thin Optical Polarizing Films Using Gold Island Films

Fabrication techniques of ultra-thin optical polarizing films using gold island films have been investigated for the near-infrared region. The polarizing films are fabricated by stretching the periodic multilayers consisting of gold island layers and glass layers. We have experimentally investigated the optimum fabricating conditions necessary to induce large optical anisotropy into the gold island layers and have formed submicrometer-thick polarizing films with an extinction ratio of ≥20 dB in a near-infrared region longer than 800 nm. These polarizing films could be useful micro-polarizers for fiber-embedded in-line optical devices, micro-optics, and hybrid integrated optics.     

自持金刚石厚膜上沉积生长ZnO薄膜及发光特性

采用磁控溅射在自持CVD金刚石厚膜的成核面上制备了ZnO薄膜,并实验研究了其生长特性和发光特性随O2和Ar流量的变化。利用X射线衍射(XRD)、光致发光(PL)光谱、电子探针(EPMA)和霍尔测量对样品进行了检测。结果表明,在O2/Ar比值约为1时沉积得到的ZnO薄膜取向较一致,呈现高阻的状态并且发光性能最好。     

薄膜的光谱发射率

本文讨论了薄膜内的多次反射对低吸收薄膜光谱发射率的影响。这里推导出的薄膜发射率的表达式与薄膜厚度d和其光学常数n(λ）和k(λ）有关。在d→∞的特殊情况下，薄膜发射率与大块材料发射率相等。给出了实际数值评价及发射率与d、n(λ）和k(λ)相互关系的更为精确的数值结果。     

氮化钛薄膜的光学性能分析

利用磁控溅射法，在不同的工艺条件下制备氮化钛薄膜。详细分析了不同工艺条件下薄膜的光谱选择特性以及相应的光学常数，通过俄歇电子能谱对薄膜的不同深度的元素成分进行了分析，由原子力显微镜测量并处理得到氮化钛薄膜的表面形貌图。结果表明，氮化钛薄膜的光学性能严格依赖于氮和钛原子数比，符合化学计量比的TiN薄膜具有良好的光谱选择性。基底加负偏压溅射可进一步改善薄膜的性能。     

Tribological Properties of MACs-APS Films

Multiply-alkylated cyclopentanes (MACs) with different molecular structure were deposited on single crystal silicon wafers coated with a thin aminopropyltrimethoxylsilane (APS) film as an adhesive layer to form MACs-APS films. The thickness, wetting behavior and nano-scale morphologies of the films were characterized by means of ellipsometry, contact angle measurement, and atomic force microscopy (AFM). The friction and wear behaviors of the thin films sliding against a Si₃N₄ ball were examined on a UMT-2MT tribometer in a ball-on-disk contact mode. The worn surfaces of the MACs-APS films and the counterpart Si₃N₄ balls were investigated with a scanning electron microscope (SEM). It was found that the water contact angles on the MACs-APS film increased with the MACs alkyl chain-length. The MACs-APS film exhibited higher load-carrying capacity and better friction reduction and anti-wear behavior as compared with the APS film. This is suggested to occur because the APS acts as a strongly bonded lubricant phase and MACs as a mobile lubricant phase in the MACs-APS film. The increase of the chain-length of the alkyl substituent in the MACs compounds resulted in improved tribological properties of MACs-APS film. It is suggested that the longer alkyl chains are much more flexible and can dissipate the mechanical energy during the shearing process more easily than the short chain compounds. MACs with the longer chains have stronger chain-chain interactions and the larger MAC molecules have stronger intermolecular interactions, resulting in the good tribological properties of MACs-APS film.