Effect of Heat Treatment on Electrical and Optical Properties of Cd₂SnO₄ Films

Cd₂SnO₄ (CTO) films prepared by radio-frequency reactive sputtering from a Cd-Sn alloy target in Ar-O₂ mixtures have been found to be a n-type degenerate semiconductor in which oxygen ,vacancies provide the donor states and free carrier concentration is up to 4.46x 10²⁶ /m³. The films were annealed at temperature up to 500°C in stable Ar flow. Large Burstein shift has been observed in the visible transmission spectra. Photoluminescence spectrum measurement indicates the intrinsic optical gap of crystalline CTO is about 2.156eV. Analysis of electrical and optical data on CTO films before and after heat treatment leads to a calculated optical band gap in the range of 2.37-2.64eV and an effective mass 0.22-0.48 of the free electron mass.