Bias assisted growth on diamond single crystals: the defect formation due to ion bombardment studied by ion channelling, electron backscatter diffraction, and micro-Raman spectroscopy

Abstract

The basic mechanisms of defect formation due to ion bombardment during bias assisted growth of diamond films were studied. Diamond films were deposited at bias voltages between −60 and –120 V for 2 h on Ib single crystals. In ion channelling experiments a steep increase in dechannelling was found: For the film grown at the lowest bias voltage of –60 V dechannelling increased by a factor of 2 as compared to the 0-V reference film. For the subsequent sample, deposited at –80 V, channelling was already completely suppressed. Analysis of backscatter Kikuchi patterns indicates that up to –85 V the decrease in pattern contrast is caused by defects in the crystal lattice equally distributed over the film rather than by variations of the crystal lattice orientation (mosaicity). According to the Raman spectra three different regimes can be distinguished: At low bias voltages up to –60 V, signal from non-diamond carbon phases is negligible. At high bias voltages of –100 V and above, the typical signature of amorphous and graphitic carbon phases is found in the spectra. In the third regime at approximately –80 V, these spectral features exhibit pronounced fine structure and a strong enhancement in intensity. Our experiments suggest that luminescence as well as resonance Raman effects contribute to the form of these spectra.