In order to investigate the charge states of a silicon vacancy, a cluster model was introduced which included both the Coulomb interaction, U, between electrons in the dangling bond and the coupling, g, between the electrons and Jahn-Teller phonons, and which was solved by using the numerical diagonalization method. It was found that, for U > 0 and g = 0, the ground state of the neutral charge state, V0, was spin singlet ( S = 0) and orbital doublet. When g was varied at finite U, the ground state changed to the orbital triplet state with S = 1 at an intermediate coupling, gc1, and finally changed to the orbital triplet state with S = 0 at a strong coupling, gc2. The result obtained for g > gc2 was consistent with the low-temperature elastic softening observed in non-doped crystalline silicon.

Cluster Model Calculations for Charge States of a Silicon Vacancy. Y.Yamakawa, Y.Ōno: Journal of Physics - Conference Series, 2009, 150[4], 042233