EFFECTS OF CHEMICAL TREATMENTS ON SIC SURFACE-COMPOSITION AND SUBSEQUENT MOS2 FILM GROWTH

The surface composition of hot-pressed silicon carbide (SiC) samples and the growth of lubricating molybdenum disulfide (MoS2) films on these surfaces are examined as a function of surface treatment. SiC samples polished in air exhibit significantly less surface silicon oxide (approximately one monolayer) relative to unpolished samples, as determined by X-ray photoelectron spectroscopy. The surface oxide and surface carbon contamination are both reduced by etching with aqueous HF under a nitrogen atmosphere. Annealing the sample to 350°C under vacuum removes still more surface carbon contamination, particularly C-0 species. The crystallographic orientation of radio frequency sputter-deposited MoS2 films on the SiC substrates at 220 °C is strongly dependent on the amount of surface contamination. As the contamination concentration decreases, more MoS2 crystallites grow with basal planes oriented parallel to the sample surface, as detected by X-ray diffraction. These results support an active site model for the growth of MoS2 films with basal planes oriented perpendicular to the surface and suggest that the active site on SiC is a chemisorbed carbon contaminant. © 1990, American Chemical Society. All rights reserved.