Transparent and conducting Zn-Sn-O thin films prepared by combinatorial approach

Zn-Sn-O (ZTO) films with continuous compositional gradient of Sn 16–89 at.% were prepared by co-sputtering of two targets of ZnO and SnO2 in a combinatorial method. The resistivities of the ZTO films were severely dependent on oxygen content in sputtering gas and Zn/Sn ratio. Except for the films with Sn 16 at.%, all the as-prepared films were amorphous and maintaining the stable amorphous states up to the annealing temperature of 450 8C. Annealing at 650 8C resulted in crystallization for all the composition, in which ZnO, Zn2SnO4, ZnSnO3, and SnO2 peaks were appeared successively with increasing Sn content. Above Sn 54 at.%, the ZTO films were deduced to have a local structure mixed with ZnSnO3 and SnO2 phases which were more conductive and stable in thermal oxidation than ZnO and Zn2SnO4 phases. The lowest resistivity of 1.9 10 3 V cm was obtained for the films with Sn 89 at.% when annealed at 450 8C in a vacuum. The carrier concentrations of the amorphous ZTO films that contained Sn contents higher than 36 at.% and annealed at 450 8C in a vacuum were proportional to the Sn contents, while the Hall mobilities were insensitive to Sn contents and leveling in the range of 23–26 cm2/V s.