Optical Constants of Amorphous, Transparent Titanium-Doped Tungsten Oxide Thin Films

We report on the optical constants and their dispersion profiles determined from spectroscopic ellipsometry (SE) analysis of the 20%-titanium (Ti) doped of tungsten oxide (WO3) thin films grown by sputter-deposition. The Ti-doped WO3 films grown in a wide range of temperatures (25-500 degrees C) are amorphous and optically transparent. SE data indicates that there is no significant interdiffusion at the film substrate interface for a W Ti oxide film growth of similar to 90 nm. The index refraction (n) at lambda = 550 nm vary in the range of 2.17-2.31 with a gradual increase in growth temperature. A correlation between the growth conditions and optical constants is discussed.