Investigation of the structure of tungsten oxide films obtained by chemical vapor deposition

¹ Central Laboratory for Solar Energy and New Energy Sources at the Bulgarian Academy of Sciences, 72 Tzarigradsko shose Blvd., 1784 Sofia, Bulgaria
² Linköping University, Department of Physics and Measurement Technology, Material Science Division, S-581 83 Linköping, Sweden
³ Sofia University, Department of Physics, 5 James Boucher Blvd., Sofia, Bulgaria

Corresponding author: dgogova@phys.bas.bg

Received: 17 April 2000
Revised: 8 August 2000
Accepted: 8 August 2000
Published online: 15 September 2000

Abstract

Thin amorphous and polycrystalline tungsten oxide films have been prepared by Chemical Vapor Deposition (CVD) from metallorganic precursor − tungsten hexacarbonyl − at atmospheric pressure. The dependence of the composition and the structure of tungsten oxide films on the technological conditions has been investigated by XPS, XRD, DTA-TGA and Raman spectroscopy. As a result it has been established that: at high values of the flow-rates of the reaction gases amorphous films of very low density have been obtained; in the XPS spectra of the understoichiometric WO_3−y (0 < y < 0.3) films besides W⁶⁺, also W⁵⁺ and W⁴⁺ states have been observed. First to observe in the Raman spectra of amorphous CVD-WO₃ films is the band at ~ 950 cm⁻¹, characteristic for terminal W⁶⁺ = O bonds in result of the presence of structural water. The existence of structural water in the amorphous material has been established by thermal analyze, also.