Multiple twinning and nitrogen defect center in chemical vapor deposited homoepitaxial diamond

Homoepitaxial diamond films were grown on polished {100} faces of single cr ystal type IIa diamond substrates using microwave plasma assisted chemical vapor deposition system. 14 homoepitaxial diamond films were grown under a variety of substrate temperatures (1000-2000 degrees C), methane concentrat ion (1-6% in hydrogen gas) and processing pressure (60-200 Torr). Electron paramagnetic resonance (EPR) studies demonstrate that nitrogen is incorpora ted as a singly substitutional impurity (P1-defect center) and the nitrogen concentration is in the range 10-100 parts per million (ppm). The substitu tional nitrogen concentration in homoepitaxial diamond was observed to decr ease with increasing substrate temperature. Multitwin percentages of ail gr own diamonds derived from EPR spectra are correlated with the growth parame ter alpha, which is simply the growth velocity along the [100] direction di vided by the growth velocity along the [111] direction. With the aid of mul titwin morphology and multitwin percentages derived from EPR, we describe c onditions under which a twin-free and low defect single crystal diamond can be grown from the vapor phase on the {100} oriented substrates. (C) 1999 E lsevier Science S.A. All rights reserved.