Paramagnetic centers in hydrogenated microcrystalline Si, µc-Si:H were studied using dark and light-induced electron-spin resonance. In dark electron spin resonance measurements only one center was observed. The g-values obtained empirically from powder-pattern line-shape simulations were g|| = 2.0096 and g = 2.0031. It was suggested that this center may be due to defects in the crystalline phase. During illumination at low temperatures, an additional electron spin resonance signal appeared. This signal was best described by 2 powder patterns indicating the presence of 2 centers. One center was asymmetrical (g|| = 1.999, g = 1.996), while the other was characterized by a large unresolved broadening such that unique g-values could not be obtained. The average g-value for this center was 1.998. The light-induced signal, which was interpreted as coming from carriers trapped in the band tails at the crystalline grain boundaries, remains for at least several minutes after the light was turned off. Although the time scales of the decay curves were very different for two samples prepared by different techniques, both decays could be fitted using the assumption of recombination due to distant pairs of electrons and holes trapped in localized band-tail states.

ESR Observations of Paramagnetic Centers in Intrinsic Hydrogenated Microcrystalline Silicon. M.M.de Lima, P.C.Taylor, S.Morrison, A.LeGeune, F.C.Marques: Physical Review B, 2002, 65[23], 235324 (6pp)