|
Wurtzitic ZnO is a wide-band gap (3.137eV at room temperature) semiconductor material which has many applications in blue and UV light emitters. The main advantages of ZnO as a light emitter are its large exciton binding energy (60 meV), with the lattice constant,. In recent years, the new interest in ZnO has recently culminated because of the several researches, such as n-doped ZnO, ZnO based DMS materials. Indeed, ZnO has found numerous applications in such diverse areas as optoelectronics, photochemistry, microelectronic. At present, the preparation of high quality ZnO is a hotspot inⅡ-Ⅵoxide semiconductor. The preparative technique of ZnO have been researched by many researchers, such as chemical vaporous deposition, chemical vaporous deposition of organometallic compounds, molecular beam epitaxy, R.F. magnetron sputtering, pulsed laser deposition, etc. In this paper, in order to do a systematic research about the effect of preparative constants to the properties of ZnO thin films, such as microstructure, the optical properties, ZnO thin film samples with preferred c-axis orientation was prepared by R.F. magnetron sputtering technique on glass substrates, the effect of Al doping, sputtering power, the ratio of argon and oxygen on the microstructure, the optical properties were researched in detail by X-ray diffraction, UV-VIS spectrophotometry, fluorescence spectrophotometry. The results of the microstructure analysis showed that the FWHM and the grain size of ZnO samples have great relationships with the Al doping, sputtering power, Ar/O2. The crystallization of the films were promoted by desirable sputtering power and Ar/O2. When the working pressure was kept in constant, the growth behavior of the ZnO thin films which was prepared by R.F. magnetron sputtering was mainly decided by the density of oxygen in the space where the samples were prepared. The absorption spectra of the samples was measured, the results showed that the films possessed a transmittance of about 80% in the visible region and a sharp optical absorption in the UV region. Furthermore, the band gap values decreased and the absorption edges of the samples exhibited the red shift with the sputtering power increased. With the increase of oxygen partial pressure, the band gap exhibited different experimental values. The photoluminescence ( PL) spectra of the samples were measured at room temperature, blue peak located at 468nm and green peak located at about 502nm were observed from the PL spectra. With the rise of the sputtering power, the intensity of the blue peak increased sharply, and the intensity of green peak in 502nm increased at the same time. It was concluded that the blue peak was mainly attributed to the interstitial Zinc (Zni ) and the green emission peak must be related to the deep level defect′s of oxygen (VO ) in the crystal of ZnO films.
|