晶面择优取向ZnO纳米棒阵列膜的制备及其光催化活性研究

采用简单、低温的方法,在修饰过的Zn片上成功制备出具有高度取向的ZnO纳米棒阵列.用SEM、XRD和PL技术对制备出的ZnO纳米棒的结构和谱学特性进行了表征,并通过降解甲基橙溶液研究了其光催化活性.结果表明,ZnO纳米棒是六方钎锌矿晶,与基底垂直,具有沿(002)晶面择优生长的特征.统计结果显示,湿化学反应24h后90%以上的ZnO纳米棒直径为80～140nm,长度为4μm.在PL谱中观察到3个荧光发射带,中心波长分别位于386nm的紫带、524nm的绿带和450～500nm附近的蓝带.ZnO纳米棒的光催化反应为一级反应,表观速率常数与甲基橙的初始浓度有关.     

Fabrication of single crystal PZT thin films on glass substrates

 We have successfully transferred heteroepitaxial Pb(Zr,Ti)O₃ (PZT) thin films from MgO substrates on to glass substrates. The transferred PZT thin films exhibit single crystal structure with ferroelectric properties similar to the as-grown epitaxial films. The transferring process comprises coating of Cr-metallized surface of epitaxial PZT thin films, pressing and cementing the Cr-metallized surface on to the glass substrates by silicone rubber, and removing the MgO substrates by chemical etching. This process realizes a fabrication of high-temperature processed PZT thin films onto the glass at room temperature. The process is also available for the transformation of PZT thin films on organic film sheet. The present transfer process reduces the effects of the inevitable strain and/or constraint to rigid substrates for heteroepitaxial growth and has a potential for integration of single crystal piezoelectric PZT devices onto a wide variety of MEMS.     

Preparation and characterization of amorphous manganese sulfide thin films by SILAR method

Manganese sulfide thin films were deposited by a simple and inexpensive successive ionic layer adsorption and reaction (SILAR) method using manganese acetate as a manganese and sodium sulfide as sulfide ion sources, respectively. Manganese sulfide films were characterized for their structural, surface morphological and optical properties by means of X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis and optical absorption measurement techniques. The as-deposited film on glass substrate was amorphous. The optical band gap of the film was found to be thickness dependent. As thickness increases optical band gap was found to be increase. The water angle contact was found to be 34°, suggesting hydrophilic nature of manganese sulfide thin films. The presence of Mn and S in thin film was confirmed by energy dispersive X-ray analysis.     

Microstructure characterization of sol-gel derived PZT films

The crystallization of sol-gel derived amorphous PZT films deposited on a MgO single-crystal substrate and a SiO₂ glass substrate was examined. The pyrochlore crystallites, 5 nm in size, were homogeneously nucleated in the amorphous films at 350 °C. The nucleation temperature of pyrochlore did not depend on the type of substrate. Fine pyrochlore grains were stable even during annealing at high temperatures up to 600 °C. The perovskite formation temperature was dependent on the substrate, and was about 550 °C on the MgO single-crystal substrate and about 750 °C on the SiO₂ glass substrate. The perovskite was heterogeneously nucleated preferentially at the substrate-film interface. Perovskite nucleation was more difficult at the SiO₂ glass-film interface than at the MgO single crystal-film interface. The ease of nucleation reflected the perovskite formation temperature. Perovskite crystals grew fairly rapidly, once they were nucleated in the films. In the multiple-coated films, the interface between successive layers of PZT films was a favourable nucleation site of perovskite, and the columnar perovskite grains passing through the interface were often developed.     

Characterization of Ti-containing amorphous carbon films prepared on titanium substrates

Amorphous carbon (a:C) films prepared on pure titanium (Ti) substrates exhibit relatively high intrinsic compressive stress. In order to obtain low stress films with varied electrical and mechanical properties, metal (Ti) ions are incorporated into the plasma. This is done with the help of metal containing carbon targets. Amorphous carbon films with varied percentage of Ti were deposited on polished pure Ti substrates using Filtered Cathodic Vacuum Arc (FCVA) technique together with substrate pulse biasing. Characterizations of the films were carried out using various equipments including Raman Spectroscopy, X-ray diffractometer, Atomic Force Microscopy (AFM), Pin-on-Disk Tribometer and Micro-Scratch Tester; and properties such as microstructure, crystallography, film stress, morphology, frictional coefficient and critical load were investigated as a function of Ti content in the target. The results suggest that the film prepared with 5 at.% Ti-containing carbon target, under 7 kV substrate pulse bias voltage, displays almost zero stress. However such films are inferior in its Tribological properties compared to that of pure a:C films.     

Preparation of highly oriented AlN thin films on glass substrates by helicon plasma sputtering and design of experiments

Aluminum nitride (AlN) thin films were deposited by a helicon plasma sputtering system with a radical cell. We investigated the effects of eight sputtering control factors on the crystal orientation of the films by design of experiments and the analysis of variance (ANOVA) in order to prepare highly oriented AlN thin films on silica glass substrates. Consequently, it was proved statistically that the distance between a target and a substrate, the sputtering pressure and the substrate temperature are significant control factors for the crystal orientation of the films. Especially, the distance is the most important factor of the eight control factors, which has not been reported so far. On the other hand, the effects of the cathode r.f. coil power, the radical cell power, the nitrogen concentration, the sputtering time and the cathode power are not statistically significant. Moreover, a detailed investigation of the dependence of the orientation on the three important control factors was carried out to optimize the sputtering conditions. The full width at half-maximum (FWHM) of the X-ray rocking curve of the film deposited under the optimized sputtering conditions is 2.4° (σ=1.3°). This orientation is the highest in the AlN thin films deposited on amorphous substrates reported to our knowledge.     

氟化非晶态碳膜(a-C:F)的制备与表征

采用等离子体浸没与离子注入装置,以CF4和CH4作为源气体,在Si(100)基片上制备了含氟量不同的一系列氟化非晶态碳膜。通过XPS、FTIR和Raman对其结构进行了表征。采用躺滴法测量薄膜与双蒸水之间的接触角。薄膜硬度通过纳米压痕仪进行测量。XPS和FTIR结果表明存在C—CF、C—Fx基团和少量的氧。我们认为薄膜中存在的氧元素是由于薄膜在正常存放时发生了时效过程,其中的悬挂键发生化学吸附反应引起的。Raman和接触角测量结果表明,随着氟元素含量的逐渐增加,薄膜从典型的类金刚石状结构逐渐转化为类聚合物状结构,接触角逐渐增大。纳米压痕测量结果表明,氟元素的加入使得薄膜的硬度有很大程度的降低。     

Control of the structure in zone-melted silicon films on amorphous substrates

In situ observations of a crystallization front (solid-liquid interface) during zone-melting recrystallization of thin silicon films on amorphous substrates by laser beams are described. Cellular structure of the front is investigated, and a transition from faceted to rounded front depending on thickness of the film is noted.     

玻璃表面超疏水性薄膜制备

采用溶胶-凝胶法,以三甲基氯硅烷、氢氟硅酸和水为先驱体,在玻璃基片上用提拉法制备出一种含有-CF3强疏水性基团的氟硅烷薄膜.通过红外光谱和扫描电镜对薄膜结构和表面形貌进行了表征和观察.并用接触角测定仪三甲基氯硅烷和氢氟硅酸在不同摩尔配比下薄膜疏水性能.结果表明该薄膜具有高度交联的不规则球状表面结构.当三甲基氯硅烷和氢氟硅酸的摩尔比为2.5:1时,薄膜具有超疏水性,对水滴的表面接触角可达156°.     

Preparation of ZnAPO-34 films on alumina substrates

The hydrothermal synthesis of ZnAPO-34 films supported on alumina substrates was reported in this paper. Synthesis parameters of the films were extensively examined. Organic content, water content, alumina source, and supports played important roles in the syntheses of ZnAPO-34 films. The best synthesis composition was found to be 0.4ZnO : 0.8Al₂O₃ : 1P₂O₅ : 2TEAOH : 225–550H₂O with aluminum isopropoxide as alumina source. However, repeated syntheses were necessary to synthesize contineous ZnAPO-34 films on both nonporous an porous alumina supports.     

纳米结构PZT铁电膜的制备及其表征

采用溶胶-凝胶(sol-gel)自旋涂敷法在硅基氧化铝纳米有序孔膜版介质上(膜版孔径尺寸20～100nm,内生长金属纳米线作为底电极一部分)制备Pb(Zr0.53Ti0.47)O3(PZT)纳米结构铁电膜,并对其介电、铁电性能及微结构进行了表征。介电测量结果表明,厚度25nm的PZT铁电膜,其介电常数在低频区域(频率104Hz)从860迅速下降到100,然后保持在100左右,直至测量频率升高到106Hz。低频区域的介电常数迅速下降是由空间电荷极化所致,它与薄膜和电极之间聚集的界面空间电荷密切相关,尤其是在薄膜与Au纳米线的弯曲界面处。介电损耗在4000Hz附近出现峰值,它来源于空间电荷的共振吸收效应。电滞回线测量结果表明,厚度为100nm的PZT铁电膜,其剩余极化强度为50μC/cm2,矫顽场强为500kV/cm。剖面透射电镜(TEM)像表明PZT纳米铁电膜与底电极(金属纳米线)直接相接触,它们之间的界面呈现一定程度的弯曲。在PZT纳米铁电薄膜后退火处理后,发现部分Au金属纳米线顶端出现分枝展宽现象;而改用Pt纳米线后可有效抑制这种现象。为兼顾氧化铝纳米有序孔膜版内的金属纳米线有序分布及PZT纳米膜的结晶度,选择合适的退火温度是制备工艺中的关键因素。     

VSSP法制备PZT陶瓷长纤维及其表征

采用纤维素和锆钛酸铅(PZT)粉体为原料,使用黏胶纺丝法(VSSP)制备了直径250μm的PZT陶瓷长纤维.利用SEM和XRD对纤维素坯和烧结后纤维进行表征并根据正交实验设计法通过实验确定了纤维成型浆料中粉体与纤维素质量比、分散剂用量以及老成时间等因素对成型后纤维素坯直径均匀度的影响,进而确定了制备PZT陶瓷长纤维的优...     

Growth and characterization of high resistivity c-axis oriented ZnO films on different substrates by RF magnetron sputtering for MEMS applications

In the present work, we report the deposition of high resistivity c-axis oriented ZnO films by RF magnetron sputtering. The deposition parameters such as RF power, target-to-substrate spacing, substrate temperature, and sputtering gas composition affect the crystallographic properties of ZnO films, which were evaluated using XRD analysis. The self-heating of the substrate in plasma during film deposition was investigated and we report that highly “c-axis oriented” ZnO thin films can be prepared on different substrates without any external heating under optimized deposition parameters. The post-deposition annealing of the film at 900 °C for 1 h in air ambient increases the intensity of (002) peak corresponding to c-axis orientation in addition with the decrease in full width at half maxima (FWHM). Bond formation of ZnO was confirmed by FTIR analysis. Grains distribution and surface roughness have been analyzed using SEM and AFM. The DC resistivity of the films prepared under different deposition conditions was measured using MIS/MIM structures and was found to be in the range of 10¹¹–10¹² Ω cm at low electric field of 10⁴ V/cm. The ZnO film of 1 μm thickness has transmittance of over 85% in the visible region. Applications of these films in MEMS devices are discussed.     

Electrical characterization of amorphous germanium dioxide films

Amorphous germanium dioxide (GeO₂) films have been deposited by electron beam evaporation onto different substrates including glass, SnO₂ conducting glass, evaporated gold and n-type silicon in order to examine the electrical behaviour of GeO₂ in metal/insulator/metal (MIM) and metal/insulator/semiconductor (MIS) structures. In MIM structures the as-deposited films are strongly influenced by electrode barriers but heat treatment at 600 K induced ohmic behaviour. The dielectric response of the films in the frequency range 0.1–100 kHz and the temperature range 180–350 K showed that the dielectric constant at 300 K was 9 and was virtually independent of frequency, while the a.c. conductivity follows the relation σ ∞ ω^s, where s is temperature dependent. Good agreement with a classical electronic hopping model is obtained. In MIS structures, GeO₂ on silicon gives rise to heterojunction behaviour at low voltages while, at higher voltages, the d.c. conduction is bulk dominated and exhibits space-charge-limited conduction. The dielectric response of MIS structures is strongly influenced by the depletion capacitance at the interface between GeO₂ and silicon.     

Structural characterization of thin amorphous Si films

We present a study of structural changes occurring in thin amorphous silicon (a-Si). The a-Si films were deposited on single-crystalline Si substrates held at room temperature or 200 °C by magnetron sputtering of a Si target in pure Ar atmosphere, and therefore the films were hydrogen-free. All samples were annealed in vacuum and subsequently studied by EPR and GISAXS. A strong decrease in the dangling bonds content at lower annealing temperatures, and then an increase of it at around 550 °C, suggested significant structural changes. In parallel the samples were studied by GISAXS which confirmed changes at the nanometric scale attributed to voids in the material. A nice correlation of the results of the two techniques shows advantages of this approach in the analysis of structural changes in a-Si material.     

Formation and characterization of silicon films on flexible polymer substrates

Polysilicon thin film transistors on flexible substrates are of considerable interest for applications in flexible displays. This paper investigates the formation of nanocrystalline silicon on flexible, transparent polymer substrates. An 800-nm layer of amorphous silicon was deposited on a polyimide substrate followed by a 20-nm layer of aluminum. Samples were rapid thermal annealed at 900 °C for 20 s, forming silicon nanocrystallites in a porous amorphous silicon film. The films were analyzed using Rutherford backscattering spectrometry, Raman Spectroscopy and cross-section transmission electron microscopy. A mechanism is proposed for the formation of silicon nanocrystallites and pores in the a-Si layer.