Characterization of W–O coatings deposited by magnetron sputtering with reactive gas pulsing

Abstract

In this study, tungsten oxide coatings were deposited by dc magnetron sputtering onto steel, glass and silica substrates using either a conventional process (constant flow of oxygen) or pulsing of reactive gas (RGP). A square wave regulation signal with different pulsing period ( T) and oxygen injection time ( t on) was used in RGP. The partial pressure of argon was kept constant for all depositions. Three series of coatings were prepared: two with constant T and increasing t on and one with different T and constant t on/ T ratio. The chemical composition, morphology and structure of these coatings were analyzed by electron probe microanalysis, scanning electron microscope (SEM) and X-ray diffraction, respectively. Preliminary studies have shown a linear relationship between t on/ T and the oxygen content ratio (O/W) in the coatings. The structure of these coatings was a mixture of β-W (W 3O) and quasi-crystalline WO 3 phases in amounts depending of the oxygen content. SEM measurements have shown that a multilayer structure was obtained with increasing pulsing period. The hardness decreased with increasing oxygen content in the coatings.