Structural properties of microcrystalline Si films prepared by hot-wire/catalytic chemical vapor deposition under conditions close to the transition from amorphous to microcrystalline growth

The structural properties of microcrystalline Si films prepared by hot-wire/catalytic chemical vapor deposition, with various dilution ratios of silane in hydrogen, were investigated as regards to the role of hydrogen. A large surface roughness correlated with a low crystalline nuclei density was observed for microcrystalline Si films deposited near the transition from amorphous to microcrystalline growth. Investigations of hydrogen-related properties suggest the presence of molecular hydrogen in these films. We tentatively propose that the diffusion of atomic hydrogen into the subsurface layer of growing films, which leads to the relaxation of amorphous Si network and to the generation of molecular hydrogen, plays an important role for determining the film properties, besides top surface reactions.     

Hydroxyapatite/Bioactive Glass Films Produced by a Sol–Gel Method: In Vitro Behavior

Hydroxyapatite (HA) and HA/bioactive glass (49S) films were deposited on Si(100) substrates by a sol–gel dip‐coating method. The microstructure and in vitro bioactivity of the films were investigated by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X‐ray photoelectron spectroscopy (XPS). Polycrystalline HA and amorphous bioactive glass films were obtained after annealing at 600 and 400 °C, respectively. The crystallization temperature of HA was determined to be around 568 °C. The surfaces of the HA films were covered with an apatite layer consists of spherulites formed by nanosized needle‐like aggregates after the soaking in simulated body fluid (SBF) for 10 days, while amorphous HA/bioactive glass surface was covered with larger spherical crystallites. Both XPS and EDS results obtained from HA/bioactive glass film, after soaking in SBF, showed increasing P amounts on the surface at the expense of Si. The higher density of the newly formed layer on HA/bioactive glass surface than that of the HA surface after 10 days of soaking was evidence of increased reaction rate and apatite forming ability when bioactive glass layer is present on the HA films.     

Fabrication of dye-sensitized solar cells using Nb2O5 blocking layer made by sol-gel method

In this study, nanocrystalline Nb2O5 thin film has been prepared via sol-gel process using niobium ethoxide as a precursor. Sol-gel films using various ratios of H2O/Nb have been prepared on fluorinated tin oxide (FTO) glass substrate, and used as electron-blocking layer of dye-sensitized solar cell (DSSC). The Nb2O5 film as deposited was amorphous, but became crystalline with hexagonal phase after heat treatment at 600 degrees C. With higher H2O/Nb molar ratio, denser and more uniform Nb2O5 film surface was obtained. DSSCs with the structure of FTO/Nb2O5/TiO2/Dye/EL/Pt/FTO have been prepared, and their solar-cell performance was evaluated. By introduction of Nb2O5 sol-gel film between FTO and TiO2 layer in DSSCs, energy conversion efficiency could be improved.     

AgInSbTe相变薄膜的热刻蚀腐蚀特性

研究了AgInSbTe相变薄膜作为一种新的热刻蚀材料的腐蚀特性。采用射频磁控溅射的方法在室温下制备了非晶态AgInSbTe薄膜, 经真空加热退火晶化. 以氢氧化钠溶液作为腐蚀剂, 研究了退火温度、腐蚀剂浓度、腐蚀时间对晶态、非晶态 AgInSbTe薄膜腐蚀特性的影响. 结果表明: 以非晶态形式存在的沉积态AgInSbTe薄膜在0.001 mol/L氢氧化钠溶液中腐蚀速度小于0.04 nm/min, 退火晶化后, 薄膜的腐蚀速度大幅度提高, 晶态和非晶态薄膜的腐蚀选择比随退火温度的升高而增大. 当腐蚀时间为20 min时, 经300℃真空退火的晶态AgInSbTe薄膜比相应非晶态的腐蚀速度高45倍以上. 腐蚀后薄膜表面质量良好(粗糙度＜1 nm, 10 μm×10 μm区域). 并对AgInSbTe相变薄膜的腐蚀机理进行了讨论.     

N-type crystalline silicon films free of amorphous silicon deposited on glass by HCl addition using hot wire chemical vapour deposition

Since n-type crystalline silicon films have the electric property much better than those of hydrogenated amorphous and microcrystalline silicon films, they can enhance the performance of advanced electronic devices such as solar cells and thin film transistors (TFTs). Since the formation of amorphous silicon is unavoidable in the low temperature deposition of microcrystalline silicon on a glass substrate at temperatures less than 550 degrees C in the plasma-enhanced chemical vapour deposition and hot wire chemical vapour deposition (HWCVD), crystalline silicon films have not been deposited directly on a glass substrate but fabricated by the post treatment of amorphous silicon films. In this work, by adding the HCl gas, amorphous silicon-free n-type crystalline silicon films could be deposited directly on a glass substrate by HWCVD. The resistivity of the n-type crystalline silicon film for the flow rate ratio of [HCl]/[SiH4] = 7.5 and [PH3]/[SiH4] = 0.042 was 5.31 x 10(-4) ohms cm, which is comparable to the resistivity 1.23 x 10(-3) ohms cm of films prepared by thermal annealing of amorphous silicon films. The absence of amorphous silicon in the film could be confirmed by high resolution transmission electron microscopy.     

射频磁控溅射TiO2/HA复合生物膜的制备与表征

将水热合成的羟基磷灰石(HA)粉与20 wt%Ti粉混合,冷压烧结成靶材。采用射频磁控溅射方法,在工业纯钛基体上沉积TiO₂/HA生物薄膜,通过扫描电镜(SEM)及其能谱(EDS)、X射线衍射(XRD)和差热分析仪(TDA)对膜层进行了表征,探讨了溅射膜的晶化工艺。结果表明:由于选择溅射和OH-损失,溅射膜由TiO₂晶体颗粒和非晶钙磷化合物组成,且其Ca/P比降低。经700℃,0.5 h水蒸气处理,非晶钙磷化合物结晶度大大提高,并部分转化为HA晶体,且处理后的溅射膜与基体间无裂纹。     

磁控溅射硅钼薄膜的抗氧化性能研究

用射频磁控溅射法在单晶Si基体上制备了硅钼薄膜,对薄膜进行真空退火处理以及高温氧化实验,借助SEM和X射线衍射仪(XRD)等仪器对退火前后的薄膜以及高温氧化后的薄膜进行了分析。结果表明沉积态的硅钼薄膜为非晶态,高温真空退火使薄膜由非晶态转变为晶态,致密的复合氧化物是硅钼薄膜具有良好的抗氧化性能的主要原因。     

Interfacial titanium oxide between hydroxyapatite and TiAlFe substrate

The interface between nano-crystalline hydroxyapatite (HA) thin films and a titanium alloy (Ti5Al2.5Fe) has been studied by means of Fourier transform infrared spectrophotometry and X-ray diffraction at grazing incidence. The HA thin films were deposited by radio-frequency magnetron sputtering in low pressure dry argon on substrates kept at low temperature or heated at 550 °C. The effect of film treatment by sputtering and annealing in humid air, as a simple, effective way of restoring the crystallinity and stoichiometry of the HA bulk, was studied in correlation with the development of a titanium oxide layer at the film-substrate interface. An interfacial TiO₂ film grew at the interface during annealing in moist air, while a TiO₂ layer diffused into the HA films when directly sputtered at 550 °C. The formation of an interfacial titanium oxide layer was inhibited by the insertion of a crystalline TiN buffer interlayer between the substrate and the HA film. Separately, the mechanical characteristics of the different HA films were monitored by nanoindentation to find out how they had been affected.     

Influence of Si(1 0 0) surface pretreatment on the morphology of TiO2 films grown by atomic layer deposition

The effect of water plasma treatment of both hydrophobic and hydrophilic Si(1 0 0) surfaces has been studied using infrared spectroscopy to monitor the various surface species present. Exposure to a water plasma results in a significant increase in the concentration of H-bonded hydroxyls and hydrides. Both atomic force microscopy (AFM) and cross-sectional transmission electron microscopy (XTEM) of TiO₂ films deposited by atomic layer deposition at 300 °C, show that the morphology of the films is dependent on the nature of the initial surface. XTEM of the early stages of growth showed that coatings on hydrophilic substrates deposited as initially amorphous and continuous films, which crystallised with further growth. However, the hydrophobic substrate produced island growth of small, crystalline grains. AFM images of 23-nm thick films showed that films deposited on hydrophobic and hydrophilic Si consisted of 35–100 and 150–350 nm crystallites, respectively. A film on water plasma treated Si, closely resembled that on the hydrophilic surface, indicating that hydroxyl groups are responsible for directing the film growth.     

IBAD钼膜与Al_2O_3(0001)单晶界面的HREM研究

采用中等能量离子束辅助沉积（IBAD）技术在单晶Al2O3（0001）基片上沉积钼膜，通过HREM等分析手段，在原子尺度上，对于钼膜及其与Al2O3单晶基体界面的显微结构进行了研究。结果表明：钼膜的晶粒呈细小柱状或纤维状，平均晶粒尺寸约为8nm，钼膜的致密度较高，膜内存在非晶组织。在钼膜与Al2O3单晶基片之间存在厚约10～15nm的非晶过渡层，在界面处未发现原子的长程扩散。非晶过渡层与钼膜界面处存在台阶，增加了钼膜的形核点。     

Microstructural study of titanium–palladium–nickel base thin film shape memory alloys

A new generation of thin film shape memory alloys has been developed with 1.65 μm thickness for micro-actuator applications. In this work, the microstructure of thin film Titanium–Palladium–Nickel (TiPdNi) shape memory alloys deposited using ion beam assisted deposition from a Ti₅₀Pd₃₀Ni₂₀ target is studied. The TiPdNi thin films were deposited with and without substrate heating during deposition. As-deposited films without substrate heating were found to be amorphous. Deposition on heated substrate produced a dense, columnar crystalline structure. Microstructures of bulk TiPdNi thin films as well as the interfacial region between the film and substrate were characterized by various techniques including transmission electron microscope, scanning transmission electron microscope, scanning electron microscope-energy dispersive X-ray spectroscopy and scanning transmission electron microscope-energy dispersive X-ray spectroscopy. A transition layer with 70 nm thickness is observed at the interface between the bulk film and silicon substrate. It is composed of three layers; two amorphous layers above the silicon substrate and a 50 nm thick twin absent layer, which was identified as B2 austenite phase by Fourier spectra analysis. In the bulk film, nano-scale grains in the range of 80–200 nm were observed. The width of twin band of the film was very narrower in the range of 5 nm.     

离子束溅射Si薄膜的纵向结晶性分析

研究了离子束溅射制备微晶硅薄膜的生长纵向结晶演化过程.纵向分布Raman光谱分析显示,当硅薄膜厚度减薄时,表面硅层的结晶峰强度明显减弱,峰位有微弱的蓝移.最薄的样品显示为非晶态结构.当Raman激光聚焦斑点向64.5nm厚的薄膜样品深层面聚焦取样时,微晶硅薄膜的结晶性先由表层向下逐渐变好,最大晶粒尺寸达3.318nm,最高晶化率达47.6%.最后,当激光聚焦斑点到达薄膜与玻璃衬底的界面孵化层时,硅薄膜显非晶态.     

Influence of substrate temperature and film thickness on the structure of reactively evaporated In2O3 films

Indium oxide films 25–550 Å thick were reactively evaporated at an oxygen pressure of about 0.27 Pa and at a substrate temperature between room temperature and 400°C. The dependence of the structure of the films on the substrate temperature and on the film thickness was studied using transmission electron microscopy and electron diffraction. It was found that thick films (about 550 Å) were amorphous at room temperature, partially crystallized at 50–125°C and crystalline at 150–400°C. The crystallinity of the films deposited at 150–250°C also depended markedly on the film thickness. Very thin films about 25 Å thick were quasi-amorphous, but with increasing film thickness the amorphous phase transformed into a crystalline phase.The thermal transformation of the amorphous films after deposition was also studied. Amorphous films about 550 Å thick deposited at room temperature and 100°C crystallized at 230°C and 210°C respectively.     

Microstructure and surface roughness study of highly crystallized μc-Si:H Films

We have deposited hydrogenated microcrystalline silicon films by standard rf glow discharge plasma CVD technique using a mixture of SiF₄, Ar and H₂ at low substrate temperatures. Although fully crystalline from the beginning of the growth, our films show a significant variation in the ratio of large (LG) and small grain (SG) with further growth, for any H₂ dilution case, though the trend changes for each case. The mean sizes of the LG and SG do not vary much with growth, but a marked variation occurs in the size of the conglomerate grains, as shown by atomic force microscopy (AFM) studies. Notably, a change in the H₂ dilution is found to affect not only the film microstructure, but also the crystalline orientation. We have shown the lateral and longitudinal growth of conglomerate grains to be highly dependent on the crystalline orientation. In studying the effect of film growth on film roughness, we have observed a linear correlation between the rms roughness as measured by AFM and the top surface layer as measured by spectroscopic ellipsometry. We have also succeeded in elucidating the growth mechanisms involved, apropos of surface roughness findings.     

On the structure and surface chemical composition of indium-tin oxide films prepared by long-throw magnetron sputtering

Structures and surface chemical composition of indium tin oxide (ITO) thin films prepared by long-throw radio-frequency magnetron sputtering technique have been investigated. The ITO films were deposited on glass substrates using a 20 cm target-to-substrate distance in a pure argon sputtering environment. X-ray diffraction results showed that an increase in substrate temperature resulted in ITO structure evolution from amorphous to polycrystalline. Field-emission scanning electron microscopy micrographs suggested that the ITO films were free of bombardment of energetic particles since the microstructures of the films exhibited a smaller grain size and no sub-grain boundary could be observed. The surface composition of the ITO films was characterized by X-ray photoelectron spectroscopy (XPS). Oxygen atoms in both amorphous and crystalline ITO structures were observed from O 1 s XPS spectra. However, the peak of the oxygen atoms in amorphous ITO phase could only be found in samples prepared at low substrate temperatures. Its relative peak area decreased drastically when substrate temperatures were larger than 200 °C. In addition, a composition analysis from the XPS results revealed that the films deposited at low substrate temperatures contained high concentration of oxygen at the film surfaces. The oxygen-rich surfaces can be attributed to hydrolysis reactions of indium oxides, especially when large amount of the amorphous ITO were developed near the film surfaces.     

连续式离子层吸附与反应法沉积CuSCN薄膜及其微观结构、光学特性研究

采用乙二醇作溶剂,以连续式离子层吸附与反应法(SILAR)实现硫氰酸亚铜(CuSCN)薄膜在ITO、TiO2薄膜以及玻璃衬底上的沉积.通过X射线衍射、扫描电镜和紫外-可见光透过谱等手段表征薄膜结晶性、表面和断面微观形貌以及光学特性.结果表明,衬底以及溶剂性质均对SILAR法薄膜沉积过程存在重要影响.ITO衬底上获得的CuSCN薄膜更为致密,呈结晶态,而TiO2薄膜衬底上的CuSCN薄膜主要由颗粒组成,为非晶态.随沉积次数增加,薄膜表面粗糙度增大,光学透过率逐渐下降.在优化条件下(ITO衬底,20次沉积循环),所得CuSCN薄膜表面致密均匀,可见光透过率约60%.     

Effects of dilution ratio and seed layer on the crystallinity of microcrystalline silicon thin films deposited by hot-wire chemical vapor deposition

We deposited microcrystalline silicon (μc-Si) by hot-wire chemical vapor deposition (HWCVD) at different thickness and dilution ratio, with and without seed layer. As the dilution ratio increased, we observed an increase in the amount of microcrystalline phase in the film, a change in the structure of the grains and a loss of the (220) preferential orientation. The films deposited over a seed layer had a larger fraction of crystalline phase than films deposited with the same parameters but without a seed layer. For high dilution ratios (R=100), most of the film grows epitaxially at the interface with the Si substrate, but a microcrystalline film slowly replaces the single-crystal phase. For low dilution ratios (R=14), the film starts growing mostly amorphously, but the amount of crystalline phase increases with thickness.     

Atomic layer deposition of tungsten using sequential surface chemistry with a sacrificial stripping reaction

Tungsten (W) films were grown with atomic layer control using a novel sequence of self-limiting surface reactions. The tungsten film growth was achieved by dividing the binary reaction WF₆+Si₂H₆→W+2SiHF₃+2H₂ into two separate half-reactions. Alternating exposures to WF₆ and Si₂H₆ in an ABAB… sequence produced tungsten deposition at temperatures between 425 and 600 K. The Si₂H₆ reactant served only a sacrificial role to strip fluorine from tungsten without incorporating into the film. FTIR spectroscopic investigations demonstrated that the WF₆ and Si₂H₆ half-reactions were complete and self-limiting at T>400 K. In situ spectroscopic ellipsometry measurements determined a tungsten growth rate of 2.5 Å/AB cycle with WF₆ and Si₂H₆ reactant exposures sufficient for complete half-reactions. The surface topography of the deposited tungsten films was flat indicating smooth film growth. The tungsten films were either amorphous or composed of very small crystalline grains and contained no measurable silicon or fluorine. These results represent the first demonstration of atomic layer deposition of smooth single-element metal films using sequential surface chemistry.     

Composition and Structure of Films Deposited from Silyl Derivatives of Asymmetrical Dimethylhydrazine

Si–N–C films were produced by remote-plasma chemical vapor deposition using silyl derivatives of asymmetrical dimethylhydrazine as precursors and were characterized by optical spectroscopy, x-ray photoelectron spectroscopy, scanning electron microscopy, and synchrotron x-ray diffraction. The results demonstrate that Si–N and Si–C bonds prevail in the films deposited using excited hydrogen, while the structure of the films deposited using excited helium is dominated by Si–N and C–N bonds. The films contain both amorphous and crystalline silicon carbonitride. The crystalline phase can be indexed in a tetragonal cell with lattice parameters a= 9.6 Å and c= 6.4 Å. The formation of the crystalline phase and the shape of the crystallites are not correlated with the deposition temperature, which gives grounds to believe that the crystallization process may occur in the gas phase or on the film surface as a result of the increase in mechanical stress with increasing film thickness.     

Study of the surfaces of CVD-WO3 films, by atomic force microscopy and spectroscopic ellipsometry

Atomic force microscopy imaging of chemical vapor deposition WO₃ films reveals the presence of domed crystallites that resemble the florets of cauliflowers with a rough surface texture. Annealing at 400 °C and above leads to further surface roughening, with estimated root mean square roughness values of 40–50 nm. Spectroscopic ellipsometry analysis shows that the surface layer becomes thicker with increasing oxygen flow rate during film deposition. This layer is predominantly amorphous for as-deposited films, and predominantly crystalline after annealing.