Electronic Structure of Band-Tail Electrons in a Si:H

Electronic structures of the light-induced electron spin resonance (LESR) centers in undoped a-Si:H have been investigated by means of pulsed ESR techniques. Overlapping LESR signals of $g=2.004\mathrm{}$ and 2.01 have been experimentally deconvoluted by using the difference in spin-lattice relaxation time between the two signals. The ${}^{29}$Si hyperfine structures of the 2.004 signal clearly show that the wave function of this center spreads mainly over two Si atoms, which suggests that the origin of $g=2.004\mathrm{}$ is electrons trapped at antibonding states of weak Si-Si bonds.