Fe掺杂对ZnO薄膜的微结构与光学性质的影响

Effect of Fe-doping on the Structural and Optical Properties of ZnO Thin Films

采用溶胶—凝胶法在石英玻璃衬底上制备了Fe掺杂的ZnO薄膜,研究了不同的Fe掺杂浓度对ZnO薄膜的微结构与光学性质的影响.利用X射线衍射分析了薄膜样品的晶向和晶相,利用原子力显微镜观测了薄膜样品的表面形貌,利用双光束紫外—可见分光光度计分析了ZnO薄膜样品的光学性质.实验结果表明:所有ZnO薄膜样品都是六角纤锌矿结构,ZnO晶粒沿C轴择优生长.质量分数为1%Fe掺入之后,ZnO薄膜的C轴择优取向进一步增强,薄膜的晶化质量也得到进一步提高.当Fe的掺杂浓度高于1%时,ZnO薄膜(002)衍射峰的强度又降低了,这可能是由于Fex+(x=2或3)和Zn2+具有不同的离子半径,大量的Fex+进入晶格取代Zn2+导致晶格严重畸变,从而影响了ZnO晶粒的正常生长.所制备的ZnO薄膜在可见光区都具有高的透射率,由吸收边估算出来的ZnO薄膜的光学带隙表明:随着Fe的掺杂浓度的提高,光学带隙逐渐展宽.

In this paper, Fe -doped ZnO thin films were prepared by a sol -gel method on quartz glass substrates and effect of Fe - doping concentration on the structural and optical properties of the films were investigated. X - ray diffraction （XRD） was used to study the crystalline orientation and crystal phase. Atomic force microscopy was employed to observe the surface morphologies. A UV - visible spectrophotometer was used to analyze the optical properties of the films. The results show that the prepared ZnO thin films in this study all have a hexagonal wurtzite structure and are preferentially oriented along the c - axis perpendicular to the substrate surface. After Fe is doped by 1% , the preferred orientation along the c -axis is further increased and the crystalline quality of the film is also further improved. When the Fe - doping concentration is above 1% , the intensity of （002） peaks drops again. The possible reason is that due to the difference in ionic radius of Fe^x＋（x = 2 or 3） and Zn^2 ＋ , when a lot of Fe^x＋ went into lattice sites substituting for Zn^2＋ , it led to large lattice distortion, which affected the normal growth of ZnO crystals. The optical band gaps evaluated from the absorption edges of the films show that with the increase of Fe content, the band gaps are gradually widened.