Improvement in crystallinity of ZnO and Zn2SiO4 phases by rf sputter deposition; effect of substrate bias

We report on enhancement in crystallinity of wurtzite ZnO and rhombohedral Zn2SiO4 phase using rf sputtering deposition with substrate bias. Substrates were kept at floating potential and subjected to a bias upto −60 V for shallow implantation of Zn and O ions in SiO on Si and local energy deposition. Crystalline Zn2SiO4 phase improved upto −20 V applied bias above which it deteriorated. Wurtzite ZnO phase formed on rhombohedral Zn2SiO4 phase and showed opposite trend and a decrease in strain. The improvement in crystallinity of ZnO phase resulted in decrease in defects identified from a decrease of visible light absorption and dark current. The mechanisms identified to be responsible for the improvement in ZnO phase and formation of zinc silicate phase is transfer of energy through elastic collisions from the plasma species to the deposited atoms on the growing film and shallow implantation of Zn and O ions into SiO/Si.