Reactivity and stability of thallium oxide for fabricating TlSnZnO toward thin-film transistors with high mobility

Thermal reaction between thallium oxide (Tl2O3) and zinc oxide (ZnO), tin oxide (SnO2) or indium oxide (In2O3) annealed at 600 °C for 18 h in the air atmosphere was investigated. From XRD results of 600 °C annealed samples, Tl2O3 had the biggest reactivity compared with ZnO. The EDX results suggest the mechanism in which the thallium atoms scattered and attached uniformly only on ZnO particles. We also analyzed XPS data to compare O 1s bond and Tl 4f bond of as-mixed samples with that of annealed samples, and found that Zn and Sn can contribute in improving Tl and O bonding stability. However, the affinity of In for Tl is weaker than that of Zn or Sn. Finally, we prepared the samples mixed with ZnO, SnO2, and Tl2O3 powder and the samples mixed with Zn2SnO4 and Tl2O3 powder annealed at 600 °C for 18 h. Results show that Zn2SnO4 has the same or more reactivity than SnO2 and ZnO mixed particle despite of the more stable and sufficient dispersion of Zn and Sn atoms. More stable TlSnZnO can be fabricated from Zn2SnO4 + Tl2O3 powder by suitable thermal processes. It is expected that TlSnZnO sputtering target can be fabricated by suitable calcination.