Evidence of the ground triplet state of silicon-carbon divacancies (P6, P7 centers) in 6H SiC: An EPR study

摘要

P6 and P7 centers, which are responsible for semi-insulating properties of SiC, were shown to be neutral Si-C divacancies (V_(Si)-V_C)° having a triplet ground state. The EPR experiments that were performed at very low temperatures and in complete darkness exclude the possibility of a thermal or optically excited triplet state and, as a result, the existing model of excited triplet state P6 and P7 centers was discarded. The optical alignment process which induces the spin polarization of the ground triplet ~3A state of the P6, P7 centers in SiC was interpreted to be caused by strong spin selectivity of the intersystem crossing (ISC) non-radiative transitions from an excited ~3E state to a metastable singlet ~1A state. The luminescence and optical absorption are caused by transitions between spin sublevels of ~3A and ~3E states. The analogy in properties of a divacancy in SiC and the N-V defect in diamond allows considering the divacancy in SiC as a potential defect for the single defect spectroscopy.