Structural, optical, and electronic properties of magnetron-sputtered platinum oxide films

Stable platinum oxide films have been prepared through magnetron sputtering and have been analyzed on the bases of energy-sensitive microanalyses, x-ray diffraction, resistivity, and optical reflectance measurements. The complex dielectric function has been determined for various oxygen contents in the film covering the wave-number regime 50 cm(-1)-lambda(-1)-50 000 cm(-1). The vibrational properties are dominated through a strong band, centered at 765 cm(-1), associated with a asymmetric stretching mode of the Pt-O bond. The films are amorphous, with chemical composition PtOx, where 1<x<2.1, and are considered as a homogeneous solid solution of PtO and PtO2. The materials system displays a conductor-insulator transition at x greater than or equal to 2, in connection with an optical band gap E(g) of similar to 1.2 eV in the fully oxidized state. The conduction mechanism over the whole range of compositions is thermally activated and is determined through a large density of localized states extending into the band gap. At x<2 the optical gap disappears, consistent with the semimetallic behavior of the materials system for this range of composition. (C) 1996 American Institute of Physics.