Co掺杂浓度对溶胶-凝胶法制备ZnO薄膜结构和光学性能的影响

Synthesis and Characterization of Co-Doped Sol-Gel ZnO Films

为了研究Co掺杂及掺杂浓度变化对ZnO薄膜结构及光学性能的影响,本文采用溶胶-凝胶法在石英玻璃衬底上制备了不同Co掺杂浓度的ZnO薄膜。通过X射线衍射(XRD)、扫描电镜、傅里叶变换红外光谱仪、二维傅里叶变换、紫外-可见分光光度计和荧光光谱仪等表征手段,结果表明:当Co掺杂浓度小于2%时,制备的薄膜均具有c轴择优取向生长、六角纤锌矿结构,薄膜致密度高、表面平整,在可见光区薄膜的平均透光率大于87%,薄膜具有较强的紫外发光特性,及较弱的蓝光、绿光发光特性,且掺杂后,蓝光峰向更长波段方向移动;当Co掺杂浓度大于2%时,XRD衍射(002)峰和光致发光谱的紫外发光强度逐渐淬灭,薄膜不再具有典型的六角纤锌矿结构晶态的ZnO薄膜特征,薄膜不能较好地形成固溶体,结晶质量下降,掺杂物质在晶粒间界相对富集并使得颗粒团聚长大、表面粗糙,光学带隙变窄、紫外波段光透过率明显变小。

The Co-doped ZnO films were synthesized in sol-gel technique on quartz glass substrate. The impacts of the synthesis conditions were evaluated. The ZnO films were characterized with X-ray diffraction, scanning electron mi- croscopy, 2-D Fourier transform infrared spectroscopy, ultraviolet visible （UV-Vis）, and photoluminescence spectroscopy. The results show that the Co content strongly affects the microstructures and optical properties of the ZnO films. For exam- ple, as the Co-content increased up to 2%, the compact smooth ZnO films, with uniform hexagonal wurtzite-structured grains, were grown. Its average transmittance was found to be over 87 % in the visible region. The film is capable of emit- ting strong UV light, and weak blue and green lights. The Co-doping resulted in a red-shift of the blue-ray peaks. As the Co content increased to 3% and 4%, its optical band gap and transmittance in the UV-range rapidly decreased, possibly because of the increasingly roughened surfaces, consisting of high defect-density, larger grains, and Co-rich grain boundaries.