Effects of Annealing Temperature on Microstructure and Electrical and Optical Properties of Radio-Frequency-Sputtered Tin-Doped Indium Oxide Films

Indium tin oxide (ITO) films (0.3 μm thick), with a doping level of 28 mol% SnO₂, were prepared by a radio frequency magnetron sputtering mehthod. The effects of postannealing on the microstructure and the electrical properties of the ITO films were investigated. The as-sputtered film showed an amorphous structure, whereas the films annealed at 350° and 510°C exhibited crystalline structures with grain sizes of 0.12 and 0.14 μm, respectively. Examination by TEM showed that the postannealing treatment induced SnO₂ precipitates along the grain boundaries. The resistivity increased with increasing postannealing temperatures. The mobility of carriers appears to be responsible for the resistivity increase in these specimens. The mobility change is discussed in connection with the SnO₂ precipitates.