反应溅射氧化锌薄膜的结构特点及性质

Structure and Properties of ZnO Films Prepared by Ion Beam Reactive Sputtering

以金属Zn(纯度为99.99%)作为靶材,采用离子束反应溅射法在玻璃衬底上溅射沉积了一系列ZnO薄膜样品。通过对薄膜样品X射线衍射(XRD)谱的分析,发现尽管溅射条件不同,但是ZnO薄膜只沿(0002)晶面取向生长。衬底温度和溅射气体的氧分压对薄膜沿c轴取向生长有影响,其中衬底温度的影响较明显。溅射过程中发现衬底温度为360℃最适合(0002)晶面的生长,在此温度下溅射获得了完全沿c轴取向生长且衍射峰最强的ZnO薄膜。室温下测量了ZnO薄膜的发射光谱,发现薄膜在紫外区(364nm附近)、蓝绿区(470nm附近)有较强的发光峰,在紫光区(398nm附近)、蓝光区(452nm附近)和红外区(722nm附近)有较弱的发光峰。ZnO薄膜在空气中退火,对薄膜的结构、发光和电学性质都有一定影响。合适的退火温度可以促进薄膜沿c轴的取向生长;退火后ZnO多晶薄膜的晶粒比未退火的略大;退火使部分发光峰的位置发生偏移并使薄膜的发光强度增强;退火使薄膜的电阻率显著增大,薄膜的电阻率随氧分压的增大而增大。

ZnO is a very useful and interesting ceramic material, since it exhibits a variety of properties such as semiconductive, photoconductive, piezoelectric and electro-optical behavior. Due to these characteristics, structure, properties and preparation methods of ZnO films have been extensively studied for practical applications. Different from other preparation methods, a series of ZnO films on glass substrate have been prepared by ion beam reactive sputtering with metal Zn （ purity 99.99% ） as target. X-ray diffraction （XRD） spectra analysis of the ZnO films indicates that the films are single （0002） -oriented growth although preparation condition changed. Temperature of substrate is a key factor on preferential orientation growth of ZnO film in （0002） direction. Ratio of Ar/O2 （ sputtering gas） has a little affection on structure of the films. 360 ℃ is a most adaptive substrate temperature for ZnO films single （0002）-oriented growth, and high quality ZnO film with absolute c-axis orientation has been successfully achieved at this temperature. Photoluminescence （PL） spectra show that some PL peaks are very strong at wave band of both ultraviolet （364 nm） and blue-green （470 nm） under excitation of 270 nm, another PL weak peaks appear at violet （398 nm）, blue （452 nm） and inpriate annealing temperature can promote single c-axis oriented growth of ZnO films, make crystal grains much bigger, luminescence intensifying and make resistance raising of the ZnO films. 400 ℃ is a optimum annealing temperature for single （0002）-oriented growth of the ZnO films and enhancing the film＇s luminescence intensity. Resistance of ZnO films increase with not only pressure of oxygen enlarging, but also substrate tem- perature raising. After 350 ℃ annealing in air, ZnO films become insulators. The results indicate the film＇s PL property has no relationship with its resistance.