Structural, optical and electrical properties of ZnO films grown on c-plane sapphire and (100)gamma-LiAlO2 by pulse laser deposition

ZnO thin films were grown on single-crystal gamma-LiAlO2 (LAO) and sapphire (0001) substrate by pulsed laser deposition (PLD). The structural, optical and electrical properties of ZnO films were investigated. The results show that LAO is more suitable for fabricating ZnO films than sapphire substrate and the highest-quality ZnO film was attained on LAO at the substrate temperature of 550 degrees C. However, when the substrate temperature rises to 700 degrees C, lithium would diffuse from the substrate (LAO) into ZnO film which makes ZnO film on LAO becomes polycrystalline without preferred orientation, the stress in ZnO film increases dominantly and the resistivity of the film decreases exponentially. (c) 2005 Elsevier B.V. All rights reserved.

Characteristics of polypyrrole (PPy) nano-tubules made by templated ac electropolymerization

Electrochemical alternating current (ac) method designed for the synthesis of polypyrrole (PPy) nano-tubule arrays is the topic of this paper. Two-step anodic aluminum oxide (AAO) membrane is used as a template. The morphology of PPy nano-tubules is observed by SEM and discussed. FTIR spectra exhibit that the peaks of PPy nano-tubules shift compared to conventional PPy film. (c) 2005 Elsevier Ltd. All rights reserved.

Structural, morphological and optical properties of ZnO thin films grown on gamma-LiAlO2 substrate by pulsed laser deposition

ZnO thin films were deposited on the substrates of (100) gamma-LiAlO2 at 400, 550 and 700 degrees C using pulsed laser deposition (PLD) with the fixed oxygen pressure of 20 Pa, respectively. When the substrate temperature is 400 degrees C, the grain size of the film is less than 1 mu m observed by Leitz microscope and measured by X-ray diffraction (XRD). As the substrate temperature increases to 550 degrees C, highly-preferred c-orientation and high-quality ZnO film can be attained. While the substrate temperature rises to 700 degrees C, more defects appears on the surface of film and the ZnO films become polycrystalline again possibly because more Li of the substrate diffused into the ZnO film at high substrate temperature. The photoluminescence (PL) spectra of ZnO films at room temperature show the blue emission peaks centered at 430 nm. We suggest that the blue emission corresponds to the electron transition from the level of interstitial Zn to the valence band. Meanwhile, the films grown on gamma-LiAlO2 (LAO) exhibit green emission centered at 540 nm, which seemed to be ascribed to excess zinc and/or oxygen vacancy in the ZnO films caused by diffusion of Li. from the substrates into the films during the deposition.

Deposition of ZnO thin films on (100) γ-LiAlO2 substrate

Optical properties for ZnO thin films grown on (100) γ-LiAlO2 (LAO) substrate by pulsed laser deposition method were investigated. The c-axis oriented ZnO films were grown on (100) γ-LiAlO2 substrates at the substrate temperature of 550 Celsius degrees. The transmittance of the films was over 85%. Peaks attributed to excitons were shown in absorption spectra, which indicated that thin films had high crystallinity. Photoluminescence spectra with the maximum peak at 540 nm were observed at room temperature, which seemed to be ascribed to oxygen vacancy in the ZnO films caused by diffusion of Li from the substrates into the films during the deposition.

Nano-modification inside transparent materials by femtosecond laser single beam

Periodic nanostructures along the polarization direction of light are observed inside silica glasses and tellurium dioxide single crystal after irradiation by a focused single femtosecond laser beam. Backscattering electron images of the irradiated spot inside silica glass reveal a periodic structure of stripe-like regions of similar to 20 nm width with a low oxygen concentration. In the case of the tellurium dioxide single crystal, secondary electron images within the focal spot show the formation of a periodic structure of voids with 30 nm width. Oxygen defects in a silica glass and voids in a tellurium dioxide single crystal are aligned perpendicular to the laser polarization direction. These are the smallest nanostructures below the diffraction limit of light, which are formed inside transparent materials. The phenomenon is interpreted in terms of interference between the incident light field and the electric field of electron plasma wave generated in the bulk of material.

用PLD法在MgO（100）衬底十生长ZnO薄膜的结构和光学特性

用脉冲激光沉积法在MgO（100）衬底上沉积了ZnO薄膜．衬底温度分别为400℃、550℃和700℃．利用X射线衍射（XRD）和光致发光谱（PL）对薄膜的结构和光学性能进行研究．x射线衍射的结果表明，在400℃和550℃下生长的ZnO薄膜具有高度c一轴择优取向．仉足当衬底温度升高到700℃时，薄膜由单一的择优取向变为有两个较强的择优取向．通过光致发光谱可以发现，在550℃下生长的ZnO薄膜具有强的紫外发射和窄的FWHM，并且紫外发光峰的强度与ZnO薄膜的结晶质量密切相关．

Three-dimensional micro- and nano-fabrication in transparent materials by femtosecond laser

Femtosecond pulsed lasers have been widely used for materials microprocessing. Due to their ultrashort pulse width and ultrahigh light intensity, the process is generally characterized by the nonthermal diffusion process. We observed various induced microstructures such as refractive-index-changed structures, color center defects, microvoids and microcracks in transparent materials (e.g., glasses after the femtosecond laser irradiation), and discussed the possible applications of the microstructures in the fabrication of various micro optical devices [e.g., optical waveguides, microgratings, microlenses, fiber attenuators, and three-dimensional (3D) optical memory]. In this paper, we review our recent research developments on single femtosecond-laser-induced nanostructures. We introduce the space-selective valence state manipulation of active ions, precipitation and control of metal nanoparticles and light polarization-dependent permanent nanostructures, and discuss the mechanisms and possible applications of the observed phenomena.

退火处理对ZnO薄膜发光特性的影响

用脉冲激光沉积法(PLD)在MgO(100)、a-Al2O3(0001)和MgAl2O4(111)衬底上沉积了ZnO薄膜，测量了它们的发射光谱，观察到430nm的蓝光发射，并研究了退火、衬底和激发波长对ZnO薄膜这一蓝光发射的影响。指出ZnO薄膜中430nm的蓝光发射是由锌填隙原子缺陷能级到价带顶能级间的跃迁以及电子从氧空位浅施主能级到价带顶能级间的跃迁两种机理共同作用的结果。在MgO衬底上沉积的ZnO薄膜在350nm光激发下蓝光发射峰最强。

Si（111）衬底上ZnO薄膜的磁控溅射法制备及表征

采用磁控溅射法在(111)单晶硅衬底上沉积了ZnO薄膜，并研究了退火温度对ZnO薄膜晶体质量、晶粒度大小、应力和光致发光谱的影响。X射线衍射(XRD)表明薄膜为高度c轴择优取向。不同退火温度下的ZnO薄膜应力有明显变化。应力分布最为均匀的退火温度为500℃。室温下对ZnO薄膜进行了光谱分析，可观测到明显的紫光发射(波长为380nm左右)。实验结果表明，用磁控溅射法在单晶硅衬底上能获得高质量的ZnO薄膜。

水热法ZnO晶体特征研究

ZnO具有优良的综合性能使其成为极有前途的下一代光电材料，水热法是一种重要的生长ZnO晶体的方法。本文对水热法生长的面积约150mm^2的ZnO晶体进行了报道，研究了晶体不同方向的生长速度、形貌特征和光学性能。X射线摇摆曲线表明晶体的质量较好。对于光学性质的分析表明晶体生长时加入H2O2能显著提高晶体的质量。494nm附近的发光带可能与氧空位有关。520nm的发光可能与Na或者Si所形成的杂质能级跃迁有关。

Al2O3衬底上生长ZnO薄膜的结构和光学特性

用脉冲激光沉积法在Al2O3（0001）衬底上沉积了ZnO薄膜。衬底温度分别为300℃、400℃、500℃、600℃和700℃。利用X射线衍射（XRD）和光致发光谱（PL）对薄膜的结构和光学性能进行研究。X射线衍射的结果表明在不同温度下生长的ZnO薄膜均具有高度c轴择优取向，衬底温度400℃时，膜的应力较小质量较高。ZnO薄膜有很强的紫外发光峰，紫外发光峰的强度与衬底温度密切相关，并发现当衬底温度从300℃增到400℃时，紫外发射峰出现6nm的蓝移。

退火对Si（111）衬底上ZnO薄膜的结构和发光特性的影响

采用磁控溅射法在硅（111）衬底上制备了C轴高度取向的ZnO薄膜，并研究了退火温度和氧气气氛对ZnO薄膜晶体质量、晶粒度大小和光致发光谱的影响。X射线衍射表明，所有薄膜均为高度C轴择优取向，当退火温度低于900℃时，随着退火温度的升高，薄膜的取向性和结晶度都明显提高。室温下对ZnO薄膜进行了光谱分析，退火后的样品均可观测到明显的紫光发射。在一定的退火温度范围内，还可以观测到明显的紫外双峰。空气中退火的样品，当退火温度达到或高于600℃还可观测到绿光发射。实验结果表明，发光峰强度随退火温度和氧气气氛不同而不

Annealing effects of sapphire substrate on properties of ZnO films grown by magnetron sputtering

The annealing effects of sapphire substrates on the quality of epitaxial ZnO films grown by dc reactive magnetron sputtering were studied. The atomic steps formed on (0001) sapphire (alpha-Al2O3) substrates surface by annealing at high temperature were analyzed by atomic force microscopy. Their influence on the growth of ZnO films was examined by X-ray diffraction and photoluminescence measurements. Experimental results indicate that the film quality is strongly affected by annealing treatment of the sapphire substrate surface. The optimum annealing temperature of sapphire substrates for ZnO grown by magnetron sputtering is 1400 degrees C for 1 h in air.

Nonpolar a-plane ZnO films fabricated on (302)gamma-LiAlO2 by pulsed laser deposition

Nonpolar a-plane (1 1 2 0) ZnO films are fabricated on (3 0 2)gamma-LiAlO2 substrate by pulsed laser deposition. When substrate temperature is low, c-plane ZnO is dominant. As growth temperature increases to similar to 500 degrees C, pure (1 1 2 0)-oriented ZnO film can be obtained. The X-ray rocking curve of a-plane ZnO film broadens sharply when growth temperature is up to similar to 650 degrees C; such a broadening may be related to the anisotropic lateral growth rate of (1 12 0)-oriented ZnO grains. Atomic force microscopy reveals the surface morphology changes of ZnO films deposited at different temperatures. Raman spectra reveal that a compressive stress exists in the a-plane ZnO film. (C) 2007 Published by Elsevier B.V.

Homoepitaxial growth of ZnO films via low-temperature liquid-phase epitaxy

Homoepitaxial ZnO films have been grown via liquid-phase epitaxy (LPE) on (000 1) oriented ZnO substrates. X-ray rocking curve revealed the high quality of the ZnO films with a FWHM of 40 arc sec. Films of thickness about 20 gm were gown in the temperature range 700-720 degrees C. The growth rate of ZnO films was estimated to be 0.3 mu m h(-1). Atomic force microscope analysis showed that the surface roughness of ZnO films was very low, which further confirmed the high crystallinity of ZnO films. (c) 2006 Elsevier B.V. All rights reserved.