Ellipsometric characterization of VO-=SUB=-2-=/SUB=-, VO-=SUB=-2-=/SUB=- : Mg, VO-=SUB=-2-=/SUB=- : Ge nanocrystalline films

Abstract

The spectra of the refractive index n(λ) and the extinction coefficient k(λ) of thin VO2, VO2 : Mg, VO2 : Ge films were measured using the ellipsometric method. For an undoped VO2 film at a wavelength λ=632.8 nm, near the insulator-metal phase transition, the n(T) and k(T) thermal hysteresis loops were studied. An interpretation of the results is given on the base of the Moss relation, the idea of a change in n(T) and k(T) with an impurity variation of the material density, and also on the base of the ideology of the Coulomb transformation of the density of states function in strongly correlated materials. Keywords: ellipsometry, vanadium dioxide, insulator-metal phase transition, strongly correlated materials.