Over-coordination and order in hydrogenated nanostructured silicon thin films: Their influence on strain and electronic properties

A set of hydrogenated nanostructured silicon films consisting of Si nanoparticles with a dense phase embedded in an amorphous matrix are analysed by means of several spectroscopic tools. Medium and short range order are determined by Raman spectroscopy and the average coordination versus the hydrogen content is measured from x-ray absorption spectroscopy. The improvement of transport properties such as the normalized photoconductivity with respect to that of hydrogenated amorphous silicon is explained by an inhomogeneous distribution of constraints in the samples. Our results on the order at different scales agree well with the paracrystalline model and suggest a well relaxed host matrix.