Investigating contaminants on thermochemically refined surfaces of CVD diamond films

Chemical vapor deposited (CVD) diamond films thermochemically polished on cylindrical steel plates are subjected to Rutherford Backscattering Spectrometry (RBS) and Scanning Electron Microscopy - Energy Diffractive X-ray Spectrometry (SEM-EDX). A diamond film polished for 25 hours at 950 °C is etched in chromic acid (K2Cr2O7 + H2SO4 + H2O) prior to RBS measurement while two other films also polished at 950 °C for 8 and 25 hours, respectively are analyzed as polished. The RBS spectra of as-polished diamond films contain peaks of iron contaminant while the surface of the etched film is devoid of iron. Moreover, the concentration/magnitude of the contaminant on the film polished for 25 hours is about 2-fold that of the film polished for 8 hours. SEM-EDX spectra taken from dark and bright spots manifest the presence of iron contaminant in as-polished films but its absence in the etched film regardless of the surface topology. Thus, the depth measured by the RBS is assumed to represent the characteristic thickness of the non-diamond carbon layer in which the iron contaminant originating from the polishing plate are embedded. The presence of silicon and oxygen bands in the SEM-EDX spectra of both as-polished and etched diamond films is attributed to their inclusion during film deposition.