The high binding energy component is probably attributed to either the presence of loosely bound oxygens on the surface of the ZnO thin films belonging to a specific species, e.g., –CO3, or corresponds to hydroxides [21]. Fig. 3(c) and 3(d) give the XPS data of Zn 2p and Zn 2p3/2 for pure and 3 mol% Al-doped ZnO ceramics, respectively.