Proceedings Article | 1 March 2019
Proc. SPIE. 10919, Oxide-based Materials and Devices X
KEYWORDS: Thin films, Magnesium, Argon, Chemical species, Sputter deposition, X-rays, Ions, Zinc, Oxygen, Zinc oxide
Band gap engineering of zinc oxide (ZnO) has gain substantial interest from past few years. Assimilation of Mg in ZnO increases band gap from 3.37 eV to 4.1 eV and it has versatile application in short wavelength UV devices. In this work, we have studied influence of growth ambient on RF sputtered Zn<sub>1−x</sub>Mg<sub>x</sub>O (x = 15%) thin films. Here, we have deposited Zn<sub>1−x</sub>Mg<sub>x</sub>O films at varying Ar/(O<sub>2</sub>) gas ratio from 4:1, 3:2, 2:3, 1:4 and 0:5 in growth ambient which yielded sample A, B, C, D and E, respectively. As the O<sub>2</sub> content in chamber decreases, (i.e. sample A), the surface recombination of O<sub>2</sub> atoms in the horizontal direction reduces as compared to that of Zn<sup>2+</sup> and Mg<sup>2+</sup>. Hence, we observed (100) orientation peak along with (002) in High resolution X-ray diffraction pattern. Reduction in full width half maximum values of the (002) peak were observed from sample A to E which suggests reduction in the Mg concentration. Photoluminescence measurement demonstrated the growth of films in Ar-rich ambient (A) lead to the formation of oxygen vacancies whereas reducing it results in grain size reduction, grain boundary–related defects formation and lower Mg concentration. X-ray photoelectron spectroscopy(XPS) spectra confirmed the reduction in oxygen vacancy peaks with increase in the oxygen concentration in the growth ambient. To summarize, Zn<sub>1−x</sub>Mg<sub>x</sub>O film grown in 3:2 ratios of Ar/O<sub>2</sub> ambient yielded superior quality with minimal defect states using RF sputtering technique.
