Nano-degradation of diamond surfaces by the thermochemical polishing technique

The surface roughness of pre-polished polycrystalline diamond films was measured by the stylus profilometer to be 30 μm and 9 μm on the growth and substrate sides respectively. SEM topographic images of the films showed that the size of the crystallites forming the films ranged between 5-40 μm. The crystallites are seen to be oriented randomly in various planes and directions. AFM measurements performed on thermochemically polished diamond films revealed that the arithmetical mean deviation was reduced to 1.3 nm and 1.5 nm on both the growth and substrate sides respectively. Raman spectra of optical grade films polished at temperatures between 950-1050°C contained lines in the low frequency regime between 100-700 cm^-1. The intensities of these lines are influenced by laser exposure time prior to measurement. The lines are tentatively attributed to nano-clusters formed by carbon particles which are left on the surfaces of the films during the polishing process. The spectra also entailed nano- and micro-crystalline graphite bands at frequencies of 1351 cm^-1 and 1577 cm^-1 respectively. These bands are attributed to disordered graphite of nano- and micro-sizes accumulated on the surface of the film as a result of thermochemical polishing