Crystalline polarity of ZnO thin films deposited under dc external bias on various substrates

Effects of the nature of substrates, either crystalline or non-crystalline, on the structure and properties of ZnO films deposited by sputtering were investigated. This study focuses mainly on the role of the external electric bias applied to substrates during magnetron sputtering deposition in controlling crystalline polarity, i.e., Zn-face or O-face, and the resulting film properties. It was found that polarity control was achieved on silica and silicon substrates but not on sapphire substrates. The substrate bias did influence the lattice parameters in the structural formation; however, the selection of the substrate type had a significant influence on the defect structures and the film properties.