Effect of annealing atmosphere and temperature on the properties of Cd 2 SnO 4 thin films

Cadmium stannate (Cd 2 SnO 4 , CTO) thin films were prepared by radio frequency (RF) magnetron sputtering deposition followed by annealing at 550∼650 °C in Ar, air, Ar/4% H 2 and Ar/CdS at atmospheric pressure. The crystallization onset of the amorphous as-deposited CTO thin films occurs at 550 °C, with highly crystallized single phase Cd 2 SnO 4 obtained at 600 °C and above. Electron mobility increases with the annealing temperature (T A ) and reaches mobilities of ∼70, ∼69 and ∼56 cm 2 V −1 s −1 for samples annealed at 650 °C in air, Ar and Ar/CdS respectively. Although the samples annealed in Ar/CdS shows relatively lower mobility, the high carrier density ∼6.6×1020 cm −3 (annealed at 650 °C) leads to a very low resistivity ∼1.7×10 −4 Ω cm and a high optical bandgap ∼3.6 eV due to Moss-Burstein shift. The resistivity of the samples annealed in air or Ar is limited by much lower carrier density.