Positron annihilation spectroscopy investigation of vacancy clusters in silicon carbide: Combining experiments and electronic structure calculations

The temperature dependence of the point defects in 6H-SiC induced by 12-MeV proton irradiation was studied by means of isochronal annealing followed by both positron annihilation spectroscopy and electron paramagnetic resonancemeasurements. The formation energies and positron lifetimes of various vacancy clusters were calculated to help in the interpretation of the experiments. The combination of the experiments and calculations enabled the identification of a negative silicon vacancy, with the lifetime of 218 ps, which is annealed between 400 degrees C and 700 degrees C. This process involves vacancy migration and formation of the V-C + V-Si cluster, with a lifetime of 235 ps. In addition, our calculations confirm the identification of several clusters proposed in previous experimental studies.