Nanostructural disorder in hydrogenated amorphous silicon

摘要

The structure of amorphous silicon and amorphous hydrogenated silicon has been investigated starting from a large model of amorphous silicon (2052 atoms). The modifications induced in a-Si model by when hydrogen is introduced have been revealed. The diffusion of hydrogen leads to a nanostructuring effect in the continuous random network of amorphous silicon. The effect of hydrogen on the distributed distortion defects in silicon network has been modelled. The most strained bonds have been broken and hydrogen wasd attached to the dangling bonbds on silicon. A free energy relaxation process was carried out in the frame of a Monte - Carlo - Metropolis procedure. There was demonstrated that, by nanostructuring, the total free energy of the model decreases. The variation of the bond stretching and bond bending energy as a function of the number of broken bonds indicated a dominant contribution of the bond bending term. The modelling shows, undoubtedly, the disappearance of many structural defects that probably are related to the deep electronic states in the gap of amorphous silicon.