掺Cd对ZnO薄膜光学性能的影响

Cd-doping Effects on Structure and Optical Properties of ZnO Thin Films

采用溶胶-凝胶法在石英玻璃上制备了不同掺Cd浓度的ZnO薄膜。X射线衍射(XRD)结果表明,所制备的薄膜具有c抽择优取向,随着Cd掺杂浓度的升高,(002)峰向低角度方向移动。UV透射曲线表明,薄膜具有明显的紫外吸收边,通过改变Cd的掺入浓度,可以使吸收边向长波方向移动并被控制在一定范围内,从而使薄膜的禁带宽度连续可调;薄膜的光致发光(PL)谱显示,ZnO薄膜的PL谱是由紫外激子发光峰和蓝光发光带组成,通过掺入Cd可使紫外带边发射的峰位向低能端方向红移,这与透射谱中吸收带边的红移相吻合,由紫外发光峰得到的光禁带宽度和由透射谱拟合得到的光禁带基本一致。对不同掺杂浓度的薄膜进行了比较,发现Cd掺入量为8%摩尔分数时ZnO薄膜具有最佳的结构性能和发光性能。

Pure and Cd doped ZnO thin films were prepared on quartz glass substrates by sol-gel method. X-ray diffraction （XRD） was used to analyze the structure properties of the thin films. It was found that all the films prepared have a preferential c-axis orientation. The peak position of the （002） plane shifted to the low angle value with the increase of Cd doping. From the transmittance spectrum, the optical absorption-edge obviously shifted to the longer wavelength with increasing Cd doping. It was found from the photoluminescence （PL） measurement that the spectrum obtained under room temperature contains two emissions bands： the violet band with a peak at 3. 24eV and the blue band at 2.70eV. As the concentration of the Cd increases, the peak of the violet emission has a red-shift to region of lower photon energy, which is coincident with the red-shift of the optical absorption. The band gap energies of Cd doped ZnO films calculated by a linear fitting method from the transmittance spectrum are consistent with those values from data of the PL spectrum. By comparison of the different spectrum with different concentrations of Cd doping, it is concluded that the ZnO：Cd thin film with concentration of 8mo1% has the optimal structure and luminescence properties.