PHOTOLUMINESCENCE STUDY OF [100] TEXTURED CVD DIAMONDS

Photoluminescence measurements in the range 1.5-2.6 eV of free-standing, highly [100] textured CVD diamond films are presented. The films were grown on silicon [100] substrates by microwave-assisted (MW) CVD from a methane/hydrogen mixture. The films show distinct luminescence peaks at 2.156 eV, whereas the 1.68 eV emission intensity is reduced compared with other MWCVD films. Many workers have interpreted the 2.156 eV emission observed in natural and synthetic high pressure, high temperature (HPHT) diamonds in terms of a nitrogen vacancy complex. This suggests that small concentrations of nitrogen are incorporated in a defect centre in [100] textured diamond films. The intensity of this photoluminescence differs from Mm to film. The colour of the films changes from white/yellowish to brown as the 2.156 eV emission intensity increases. Therefore we consider this intensity to be a further important parameter for the growth and characterization of defect-free diamond films.