Calculation of positron annihilation characteristics of six main defects in 6H -SiC and the possibility to distinguish them experimentally

We have determined positron annihilation characteristics (lifetime and Doppler broadening) in six basic vacancy-type defects of 6H-SiC and two nitrogen-vacancy complexes using ab initio calculations. The positron characteristics obtained allow us to point out which positron technique in the most adapted to identify a particular defect. They show that the coincidence Doppler broadening technique is the most relevant for observing the silicon vacancy-nitrogen complexes, VSiNC, and carbon vacancy-carbon antisite ones, VCCSi. For the other studied defects, the calculated positron characteristics are found to be too close for the defects to be easily distinguished using a single positron annihilation technique. Then it is required to use complementary techniques, positron annihilation based or other.