The Influences of Annealing Temperature on the Crystal Phase and Microstructure of the WO3 Thin Film

The tungsten oxideWO3 thin film was prepared by sol-gel process through peroxotungstic acid (PTA). The crystal phase and surface morphological features change at different annealing temperatures. The WO3 thin film is amorphous at 300 °C. When the annealing temperature is increased to 400 °C, it becomes monoclinic phase. The phase begins to become triclinic at 550 °C. The phase then changes to orthorhombic phase at 750 °C. With the increasing of the annealing temperature, the continuum of the WO3 thin film is broke and the gabs among grains become larger. The WO3 thin film is almost disappear after annealed at 850 °C.