Carbon formed by hydrothermal treatment of alpha-SiC crystals

The hydrothermal behavior of alpha-SiC crystals has been studied in the tem perature range 500-700 degrees C under 30-200 MPa pressure at different pH values. The extent of carbon formation via selective oxidative extraction o f Si out of the SiC crystal lattice and the structure of the carbon formed depends on the experimental conditions. Homogeneous carbon coatings were ob tained on machined crystal surfaces at ca. 600 degrees C and p greater than or equal to 60 MPa using distilled water. They were analysed using TEM, SE M, optical microscopy, micro-Raman spectroscopy, photoelectron spectroscopy , Auger spectroscopy and SIMS. The films consist of hydrogenated carbon whi ch contains up to 13 atom% oxygen on the surface and ca. 3 atom% oxygen in the bulk. Predominantly amorphous sp(2)-carbon formed, which shows little t endency to form turbostratic disordered or partly crystallized graphite. Ho wever, some particles containing nanocrystalline diamond were also found. A mechanism for hydrothermal carbon formation is proposed. The different met hods for carbon analysis applied are compared.