Investigation of the Microstructure, Porosity, Adhesion, and Optical Properties of a WO3 Film Fabricated Using an E-Beam System With Ion Beam-Assisted Deposition

The relationship between the oxygen pressure, porosity, adhesion, and ion beam-assisted deposition (IAD) conditions for WO₃ electrochromic films prepared using an electron-beam (E-beam) system was investigated. The adhesion of thin films on the substrate by sole E-beam system is very weak. The best method is proposed to obtain good adhesion and better porosity by combining the E-beam evaporation, and the microstructure and coloration efficiency were determined using a field emission scanning electron microscope (SEM) and a spectrometer, respectively. Notably, the effect of the oxygen pressure on the coloration efficiency and porosity of Ta₂O₅/WO₃ films was found to be different. The optimal average transmittance of the electrochromic film in the bleached state was 11%, and in the colored state was 68%, when a Ta₂O₅ thin film was deposited in oxygen at a pressure at 9 × 10^-4 torr using IAD, and a WO₃ thin film was deposited at an oxygen pressure of 7.5 × 10^-5 torr. The studied results are useful for the design of more efficient photoelectrochemical devices employing evaporated WO₃ films.