Spectroscopic ellipsometry determination of the optical constants of titanium-doped WO3 films made by co-sputter deposition

Articles you may be interested in Optical properties of nanocrystalline WO3 and WO3-x thin films prepared by DC magnetron sputtering Dynamic in situ spectroscopic ellipsometric study in inhomogeneous TiO 2 thin-film growth Electrical and optical properties of Sn doped CuInO 2 thin films: Conducting atomic force microscopy and spectroscopic ellipsometry studies Real-time spectroscopic ellipsometry study of Ta–Si–N ultrathin diffusion barriers Titanium (Ti) doped tungsten oxide (WO 3) thin films were grown by co-sputter deposition of W and Ti metal targets. The sputtering powers to the W and Ti were kept constant at 100 W and 50 W, respectively, while varying the growth temperature (T s) in the range of 25–400 C. The structural quality of Ti-doped WO 3 films is dependent on T s. Ti-doped WO 3 films grown at T s < 400 C were amorphous. A temperature of 400 C is critical to promote the structural order and formation of monoclinic, nanocrystalline films. The optical constants and their dispersion profiles determined from spectroscopic ellipsometry indicate that there is no significant inter-diffusion at the film-substrate interface for W-Ti oxide film growth of $40 nm. The index refraction (n) at k ¼ 550 nm varies in the range of 2.15–2.40 with a gradual increase in T s. Lorentz-Lorenz analysis (n (k) ¼ 550 nm) of the data indicates the gradual improvement in the packing density coupled with structural transformation accounts for the observed optical quality of the Ti-doped WO 3 films as a function of T s. A correlation between the growth conditions and optical constants is discussed.