Observation of new ESR signals in undoped, slowly depositeda-Si anda-Si:H

Instead of the usual dangling-bond line (g≃2.0055), ESR signals with g=2.0041 and g=2.012 were observed in pure a-Si and a-Si:H films sputtered at low deposition rates $d_r$. This is interpreted in terms of the formation of defect complexes thus indicating low $d_r$ to allow a more pronounced relaxation of the lattice. ESR data along with resistivity measurements reveal the band-gap nature of the defects concerned. If we identify the observed signals with very similar ones observed via dark ESR in a doped a-Si:H, then a previous interpretation of the latter signals as originating from band-tail states is found to be erroneous.