Effects of annealing on silicon vacancy brightness

Recently, working with Johns Hopkins APL, we started looking at the effects of annealing and quenching on the relative brightness of the V2 vacancy in 4H-SiC. The V1 and V2 vacancies are the emission from the two non-equivalent point defect sites where the irradiation (in this case, from neutron irradiation) has knocked out a silicon. The V2 has the spin characteristics that we like to see in spin qubits. You can only see the sharp, atomic-like "zero phonon line" emission from these defects at cryogenic temperatures. We have been using the Montana Instruments closed-cycle optical cryostat with the home-built microscope head to measure the photoluminesence for these samples.