Quantitative analysis of carbon distribution in steel used for thermochemical polishing of diamond films

Cylindrical steel plates used for the thermochemical polishing of CVD diamond films at elevated temperatures are investigated regarding their carbon content using X-ray and ion beam analysis. The surface distribution of carbon is investigated at randomly selected areas on two plates - one virgin and another on which a CVD diamond film is polished for one hour at 950°C. The investigation is carried out with a Scanning Electron Microscope (SEM) operated at an energy of 5 keV. Analysis of the SEM-EDX spectra manifest inhomogeneity in the surface distribution of carbon on both steel samples. Moreover, the absolute concentration of carbon on the steel plate on which diamond is polished for one hour almost triples that of the virgin sample. Elastic Recoil Detection Analysis (ERDA) depth profiling is performed on several steel plates used to polish as grown CVD diamond films for periods between 0.5-8 hours at 950°C. ERDA carbon profiles show inhomogeneity for three samples on which polishing is successively done for 8 hours. Raman spectra of post-polished steel plates reveal graphite bands and C-Hn complexes at exactly the wave numbers they appear on the diamond samples. This is a clear manifestation that the steel surfaces do not necessarily contain only atomic carbon after thermochemical polishing.