Nano-structured WO₃ Thin Films Deposited by Glancing Angle Magnetron Sputtering

Nano-structured tungsten oxide (WO3) thin films were deposited at room temperature by glancing angle reactive magnetron sputtering and then annealed at 450 degrees C in air. The films were characterized by field-emission scanning electron microscope (FE-SEM) and X-ray diffraction (XRD). The WO3 thin film deposited by DC magnetron sputtering at 80 degrees glancing angle exhibited oblique nano-column structure, while deposited by pulsed DC magnetron sputtering at the same angle exhibits nano-pore structure. After annealing at 450 degrees C for 3 h, the oblique nanocolums are conjunct with each other but the nano-pore structured remains with bigger pore size. XRD analysis reveals that WO3 thin films deposited at room temperature demonstrate amorphous structure. The amorphous structure will transfers to monoclinic phase after annealing at 450 degrees C for 1 h. Transmittance difference between colorization and bleaching of nano-structured WO3 thin film reaches 60% at wavelength of 600 nm. Electrochromic properties of nano-structured WO3 thin films are highly reversible.