Optical and Structural Study of ZnO Thin Films Deposited by RF Magnetron Sputtering at Different Thicknesses: a Comparison with Single Crystal

Optical characterizations of preferred orientation (002) ZnO thin films, prepared by RF magnetron sputtering under pure argon plasma, with different thicknesses have been investigated, where grain size and resistivity increase with thickness. Energy band gap and refractive indices have been calculated. A correlation between band gap values and crystalline quality, which is improved with thickness, has been discussed. The calculated refractive indices of the thicker deposited films have increased as the thickness increases. Full width Half Maxima (FWHM) of band gap Photoluminescence (PL) emission decreases with thickness increasement due to quality improvement as it has been monitored by X-Ray Diffraction (XRD). A comparison between PL spectra of 1200 nm film and ZnO single crystal at low temperature is found to be similar.本研究针对纯氩等离子体环境下通过射频磁控溅射（RF magnetron sputtering）制备的不同厚度（002）晶面择优取向氧化锌（ZnO）薄膜开展了光学表征，结果显示薄膜的晶粒尺寸与电阻率均随厚度增加而增大。研究中计算了薄膜的能带隙与折射率，并探讨了能带隙数值与晶体质量之间的关联——晶体质量随薄膜厚度增加而提升。计算结果表明，沉积薄膜的折射率随厚度增加而升高。通过X射线衍射（X-Ray Diffraction, XRD）监测到晶体质量随厚度提升而改善，使得能带隙相关光致发光（Photoluminescence, PL）发射的半高宽（Full width Half Maxima, FWHM）随厚度增加而降低。低温下1200 nm厚度薄膜的PL光谱与氧化锌单晶的PL光谱对比结果显示二者高度相似。