Reactive magnetron synthesis and study of the structure and optical properties of thin-film tungsten oxide doped with molybdenum

Cationic doping of tungsten oxide with molybdenum was applied to obtain an electrochromic cathode material, the spectral transmission of which can be controlled by the doping level. A series of samples was synthesized by reactive magnetron co-sputtering of metalic tungsten and molybdenum in a mixture of argon and oxygen gases. Morphology, structure, elemental and valence composition of constituent elements of the films were characterized by scanning electron microscopy, X-ray diffraction, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. Optical properties were measured using transmission spectrophotometry and spectroscopic ellipsometry. With an increase in the doping level, the resulting films acquire a gray color and become low-transparent. The ellipsometric studies have shown that enhancement of the absorption occurs both in the short-wavelength and long-wavelength parts of the visible light and adjacent parts of the spectrum. This leads to a mutual compensation of colorings, resulting in an almost achromatic change in the optical transmission and thus improving the consumer qualities of the electrochemical material and devices based on tungsten oxide.