Investigation of non-diamond carbon phases and optical centers in thermochemically polished polycrystalline CVD diamond films

Polycrystalline chemical vapor deposition (CVD) diamonds films grown on sil icon substrates using the microwave-enhanced CVD technique were polished us ing the thermochemical polishing method. The surface morphology of the samp les was determined by optical and scanning electron microscopes before and after polishing. The average surface roughness of the as-grown films determ ined by the stylus profilometer yielded 25 mum on the growth side and about 7 mum on the substrate side. These figures were almost uniform for all the samples investigated. Atom force microscopic measurements performed on the surface to determine the average surface roughness showed that thermochemi cal polishing at temperatures between 700 degreesC and 900 degreesC reduced the roughness to about 2.2 nm on both the substrate and growth sides of th e films. Measurements done at intermittent stages of polishing using confoc al micro-Raman spectroscopy showed that thermochemical polishing is accompa nied by the establishment of non-diamond carbon phases at 1353 cm(-1) and 1 453 (-1) at the initial stage of polishing and 1580 cm(-1) at cm the interm ediate stage of polishing. The non-diamond phases vanish after final fine p olishing at moderate temperatures and pressures. Photoluminescence of defec t centers determined by an Ar+ laser (lambdal(exct) = 514.532 nm) showed th at nitrogen-related centers with two zero-phonon lines at 2.156 eV and 1.94 5 eV and a silicon-related center with a zero-phonon line at 1.681 eV are t he only detectable defects in the samples.