溶胶-凝胶法制备Zn_(1-x)Mg_xO薄膜及其发光性质

Preparation and Luminescence Properties of Zn_(1-x)Mg_xO Thin Films by Sol-gel Method

采用溶胶-凝胶工艺在玻璃衬底上制备了Zn1-xMgxO(x=0.1,0.2,0.3,0.4,0.5,0.6,0.7)薄膜。X射线衍射(XRD)谱测试结果发现:在0.1<x<0.3范围内,薄膜仍然保持纯ZnO六角纤锌矿结构,(002)面衍射峰位向大角度方向移动;x>0.3时出现MgO立方相。薄膜光致发光谱研究表明紫外发光峰随Mg含量的增加向短波方向移动,且随着退火温度的升高发生明显蓝移,禁带宽度增大。但是退火温度为590℃的样品较560℃样品的发光峰出现红移。

ZnO is an interesting wide direct band gap Ⅱ-Ⅵ semiconductor with wurtzite structure. The high quality ZnO thin film is one of most potential membranous materials at present. Zinc oxide with high stability and a direct band gap of 3.37 eV has attracted tremendous attention because of its high potential for applica- tion as short wavelength optical devices. In recent studies, it is found that doping of other elements can broad the band gap of ZnO films. This will be beneficial to the development of optical devices. There are many methods to prepare ZnO films, such as pulsed laser deposition, reactive thermal evaporation, reactive magnetron sputtering, electrodeposition, sol-gel and so on. Sol-gel method has many advantages, may prepare big area semiconductor thin film, fit for industry production, and so on. In order to prepare ultraviolet optical device, study on how to broad the band gap of ZnO is very important. In this paper, in order to study the effect of Mg concentration and annealing temperature on the microstructure and band gap of Zn1-xMgxO films, the Zn1-x- MgxO （x = 0. 1, 0.2, 0, 3, 0.4, 0.5, 0.6, 0.7） thin films were prepared on glass substrate by the method of solgel. The grown films were characterized by means of X-ray diffraction, photoluminescence spectroscopy and transmission spectrum. The XRD results show that when the value of x is between 0. 1 and 0.3, the thin film remains the structure of hexagonal wurtzite and the angle of diffraction peak becomes bigger with increasing x, MgO impurity phase segregated at x ≥0.4. According to PL spectra, the thin films show an intensive UV emission peak due to the near band-edge emission and a weak UV emission peak around 403 nm between 340 nm and 520 nm at room temperature, and the intensive UV emission peak have the blue shift with the content of Mg increasing from 0. 1 to 0.3. It indicates that the band gap of ZnO was broaden with increasing Mg-doping concentration from 0. 1 to 0. 3. According to the transmission spectrum of Zn1-xMgxO （x =0.3, 0. 4, 0. 5, 0. 6, 0.7） films, it is found that absorption edges are formed when incident wavelength A 〈 350 nm and blue shifted with increase in Mg content. It also indicates more doping Mg may broad the band gap of Zn1-xMgxO. Meantime, annealing temperature also can broad the band gap obviously, but the band gap decreases when annealing temperature is above 590 ℃. Though the doping of Mg can broad the band gap, but high Mg doping can result in precipitation of MgO. Therefore, we must control Mg content and annealing temperature strictly when an optical device is prepared.