EFFECT OF OXYGEN ON BORON DOPING IN CHEMICAL VAPOR-DEPOSITION OF DIAMOND AS DEDUCED FROM CATHODOLUMINESCENCE STUDIES

Diamond films were grown using microwave-plama enhanced chemical vapor deposition. Boron doping in these films were achieved by using 0-1 ppm diborane (B2H6) in the reaction gas mixture during the deposition process. Some samples were deposited using 0.1% oxygen in the reaction gas mixture. We have employed cathodoluminescence to analyze the deposited diamond films and found that the boron concentration in diamond films is significantly reduced when oxygen was used in the deposition. For example, our result indicates that the boron concentration in films doped with 1.0 ppm B2H6 with the addition of 0.1% oxygen is close to that of films doped with 0.01 ppm B2H6 without using oxygen. Therefore, the probability of boron incorporation in diamond films is reduced by a factor of roughly 100 when 0.1% oxygen is used compared with the case where no oxygen is used.