Negatively charged Si vacancy in 4H SiC: A comparison between theory and experiment

We use electron paramagnetic resonance and electron nuclear double resonance to identify the negatively charged Si vacancy in neutron-irradiated $4H$ SiC. The identification is based on resolved ligand hyperfine interactions with carbon and silicon nearest and next nearest neighbors and on the determination of the spin state, which is $S=3/2.$ The magnetic resonance parameters of VSi^- are almost identical for the polytypes $3C,$ $4H,$ and $6H.$ The experimental findings are supported by theoretical ligand hyperfine interaction data based on a total-energy calculation using the standard local-density approximation of the density-functional theory.