Effect of boron incorporation on the `quality' of MPCVD diamond films

We report the morphology and Raman signals of MPCVD (microwave-plasma-assisted chemical vapour deposition) boron-doped diamond films deposited on Si with a B:C ratio in the gas phase ranging from 20 to 10 000 ppm. The crystal shape remains cubooctahedral in the whole range of doping, while the growth rate is reduced as B:C increases. Up to B:C = 400 ppm the full width at half-maximum (FWHM) and a very weak 1500 cm-1 component decrease as the B:C ratio increases. From B:C = 1000 ppm, an asymmetric deformation is observed in the Raman spectra and at the same time the FWHM and the 1500 cm-1 component increase with increasing B:C. For the highest B:C ratio of 10 000 ppm additional bands appear around 550 and 1220 cm-1.