Tunneling states in tetrahedrally bonded amorphous semiconductors

Using molecular dynamics, we construct a structural model of amorphous silicon which produces well-relaxed and long-lasting structures with radial distribution functions that agree well with experimental results. The model produces a sufficient number of double-well potentials with low asymmetries, enabling a structurally-explicit microscopic portrayal of tunneling states in covalently bonded amorphous systems. A new structural characterization method is used to identify the possible origin of the tunneling states in amorphous silicon. Based on the study of the short-range order, we suggest that the tunneling states in amorphous silicon are predominantly associated with dangling bonds.