After doping with lithium perchlorate, thickness of tungsten oxide thin film is 270nm, its property is improved, the film become smooth and dense, surface charge density increases, light absorption difference before and after discoloration can reach 52.9%. After doping, the crystalline temperature doesn’t change, the optimum thermal deposition temperature is still 220 degree Celsius.
Using scanning electron microscope to zoom the surface condition of thin film sample for 5.5k times, it is found that cross-sectional thickness of each sample is consistent, from the below chart we can see that after doping with lithium perchlorate, average thickness of thin film is around 2700nm. Compared to the original tungsten oxide thin film, the defect on the surface of thin film decreases, the pores nearly disappear, its density largely improved. Take the below chart as example, which can clearly show the surface of tungsten oxide thin film after doping with lithium perchlorate. No 9 sample has good apparent dense, but there are too many white particles, it may be caused by the precipitation of lithium perchlorate during doping process. No 10 sample has no white particles, but there are some little pores and cracks on the film. It means the ratio is uneven. Surface of sample 15 has smooth surface and there are no obvious residue, the surface property is great.