Oxygen-related centers in chemical vapor deposition of diamond

Diamond films are grown using microwave-plasma-enhanced chemical vapor deposition (CVD). Some samples are deposited using 0.1% oxygen in the reaction gas mixture. We have measured the cathodoluminescence spectra of these diamond films (at 77 K) and found that there is a significant difference between the samples grown with oxygen and those without oxygen. Some of the impurity-related luminescence peaks are reduced in intensity or disappear when 0.1% oxygen is used. On the other hand, there are new spectral features in the films grown with oxygen. We attribute some of these new features to oxygen-related centers in diamond and conclude that oxygen could incorporate into the diamond lattice during the CVD process.