Structural defects and hydrogen clustering in amorphous silicon

We have studied by small angle X-ray scattering the structural evolution on the atomic and nanoscale of hydrogenated amorphous silicon prepared both by ion implantation and by plasma-enhanced chemical vapor deposition and containing a similar H content. Results show that the initial structure of both samples is homogeneous on the nanoscale. Upon annealing, low-density features on the nanometer scale nucleate in both materials. However, the volume fractions of the nanoscale H-rich defects detected upon annealing and the temperature range of their evolution differ in the two cases. We propose that the initial structural disorder state of the matrix determines the initial H configurations and thereby their evolution upon annealing.