A high-frequency pulsed electron paramagnetic resonance electron-nuclear double-resonance study was made of 13C-enriched 6H-type monocrystals. It was noted that this type of spectroscopy, due to its superior spectral resolution, permitted the obtention of detailed information concerning the electronic structures of shallow B acceptor centers in this material. It was concluded that about 40% of the spin density was localized in the pz orbital of a C atom which was nearest to the B atom. The pz orbital was directed along the C-B link, and was parallel to the c-axis, in the case of the hexagonal site. It was 70 away from the c-axis in the case of the 2 quasi-cubic sites. It was concluded that the C-B bond was a dangling bond, that the B was neutral, and that there was no direct spin density on the B. There was a relaxation of the C atom which carried it away from the B atom. On the basis of a 29Si and 13C electron paramagnetic resonance electron-nuclear double-resonance study, it was further concluded that some 60% of the spin density was distributed in the crystal, with a Bohr radius of 0.22nm.

T.Matsumoto, O.G.Poluektov, J.Schmidt, E.N.Mokhov, P.G.Baranov: Physical Review B, 1997, 55[4], 2219-29