Abstract
We present measurements of the energy distribution of interface states at grain boundary areas in fine-grained silicon films. A dc method as well as ac-admittance spectroscopy reveals exponentially decaying band tails in the two-dimensional density of states within the band gap. The experimental results are in agreement with a model of potential fluctuations. This model explains the extrapolated band-edge values of the density of states as well as the ratio of the slopes of conduction- and valence-band tails.