Local structural changes induced by ion bombardment in magnetron sputtered ZnO: Al films: Raman, XPS, and XAS study

Negative oxygen (O-) ions in the sputter deposition of oxides play a non-negligible role in determining their structures as well as physical properties. Knowledge of bombardment by O- ions induced local disorder in magnetron sputtered ZnO: Al (AZO) films is of fundamental interesting whereas that is currently limited. Here we report our initial results of the local structural changes characterized by a combination of Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and X-ray absorption spectroscopy (XAS). The bombardment conditions during the film deposition was varied through changing the discharge voltage (i.e., vertical bar V-d vertical bar = 80-220 V) and the substrate positions (i.e., center or erosion region of the target). We found that highly-energetic O- ions bombardment induced a coexistence of various point defects such as oxygen vacancies (V-O), oxygen interstitials (O-i), and zinc interstitials (Zn-i). The concentration of these defects and thus the local disorder can be noticeably reduced through decreasing the vertical bar V-d vertical bar down to a sufficient low level. These results can be used to further optimize the growth processes to achieve the ZnO-based and related thin films with a high structural order.