Orientation of rf-sputter-deposited MoS2 films

Abstract

A theory to predict the orientation of radio-frequency (rf) sputter-deposited MoS₂ films with respect to the substrate surface is presented. Oxygen-containing species such as H₂O and -OH are postulated to be active sites that force crystallites to form with their basal planes perpendicular to the surface. X-ray diffraction is used to determine the crystallite orientation in films deposited on smooth, rough, or oxidized Si surfaces, as well as on fused silica or gold surfaces. The results support the theory. To produce MoS₂ films with their crystallite basal planes parallel to a substrate surface (which has been suggested to be the low friction orientation), the active sites must be removed from the substrate by, for instance, heating in vacuum.