Phase transformation and dielectric properties of sputtering-prepared Zn–Ti–O thin films

Abstract

Abstract Zn–Ti–O films were co-sputtered from Zn and Ti targets and then annealed at temperatures ranging from 600 °C to 900 °C for 2 h under an air atmosphere. The [Ti]/([Ti]+[Zn]) ratio decreased from 75.52 to 28.26 as the Zn-target power increased from 25 W to 75 W. The phase transition of the films strongly depended on the [Ti]/([Ti]+[Zn]) ratio. High [Ti]/([Ti]+[Zn]) ratios led to the coexistence of ZnTiO3, Zn2Ti3O8, and rutile TiO2 phases. Zn2Ti3O8 gradually became the major crystalline phase as the [Ti]/([Ti]+[Zn]) ratio and rutile TiO2 and ZnTiO3 phases decreased. The aforementioned phases disappeared when the [Ti]/([Ti]+[Zn]) ratio was especially low. In their place, Zn2TiO4 and even ZnO phases developed. The dielectric constant of the films increased with increasing [Ti]/([Ti]+[Zn]) ratio. However, extremely high [Ti]/([Ti]+[Zn]) ratios increased the dielectric loss of the films. The film mainly composed of the Zn2Ti3O8 phase exhibited optimal dielectric properties, including a dielectric constant and loss equal to 40.1 and 0.0304, respectively, at 1 MHz.