Electron paramagnetic resonance studies of multi-defect clusters in neutron irradiated silicon carbide

摘要

High-temperature stable defect complexes in 6H-SiC crystals created by heavy neutron irradiation and following high-temperature annealing have been discovered by electron paramagnetic resonance. After thermal annealing at 1500℃ at least five new axially symmetric centres with electron spin S = 1/2 and S = 1 were shown to arise in 6H-SiC crystals. The striking feature of all discovered centres is a strong hyperfine interaction with a great number (up to 12) of equivalent host Si (C) atoms. Two models, a four-vacancy complex V_(Si)-3V_C, and a split-interstitial antisite (C_2)_(Si) or a pair of two antisites (C_2)_(Si)-Si_C are discussed. As a result of multi-defect cluster decay new triplet centres labelled as N-V have been observed in 1900℃ annealed 6H-SiC crystals which were concluded to consist of silicon vacancy and carbon substitutional nitrogen in the adjacent lattice cites oriented along the c-axis. The parameters of these centres are similar to those for the well-known N-V centre in diamond.