STABILITY OF VACANCIES IN AMORPHOUS-SILICON

A detailed molecular-dynamics study of the relaxation of vacancies in a-Si has been performed. Our calculations reveal that of a number of vacancies introduced in the model at low temperature, roughly a third of the vacancies are stable, i.e., survive for times much larger than the characteristic time for annihilation; these, however, anneal upon heating at room temperature. Our study supports claims by experiment that relaxation in a-Si proceeds primarily by the elimination of defects. A vacancy seems, in most cases, to consist of a relatively large empty volume bounded by four atoms of which at least one is undercoordinated.