An investigation of structural defects in diamond films grown at low substrate temperatures

The incorporation of defects and impurities in CVD diamond films grown at s ubstrate temperatures between 340 and 740 degrees C has been studied. Raman and infrared spectroscopy (FTIR) investigations reveal that the observed a ccumulation of structural defects in the low-temperature growth of diamond films is coupled with a strongly increasing incorporation of hydrogen. The defects formed at low substrate temperatures are mainly of the sp(3) bondin g type, whereas sp(2) bonding defects seem to be less important. The domina nt spectral features of films with decreasing phase purity are the sp(3)CH( x) stretch region in FTIR spectroscopy, a non-assigned Raman peak centered well below 1500 cm(-1) in Raman spectroscopy and intense luminescence signa ls. The spectra have been decomposed in order to examine the temperature de pendence of various defect signals. It was found that the incorporation of defects and impurities depends on nitrogen contamination of the gas phase. and increases exponentially when the substrate temperature for CVD diamond film growth is reduced. (C) 1999 Elsevier Science S.A. All rights reserved.