The properties of powder particles incorporated in a-Si:H films

Abstract

We have found powder particles incorporated in device quality a-Si:H films. Investigations carried out by atomic force microscopy (AFM) have shown that these particles are of ∼200 nm in diameter and are more fragile than the rest of the film. SiH-stretching absorption bands in a-Si:H films consisted of two bands with frequencies of about 2020 and ∼2100 cm−1. Both peaks shift to higher frequencies with the increase of a volume fraction of powder particles. Taking into account the predictions of the chemical induction model, we conclude that this shift is due to high local hydrogen content in the powder particles which also explains their low hardness. It was found that the density of valence band tail states increases with the enlargement of particle surface areas. At the same time, the Urbach energy and the optical gap remain in the ranges of 50 to 70 meV and of 1.7 to 1.8 eV, respectively, indicating the good electronic properties of investigated films.