Hopping conduction in hydrogenated amorphous Si1-yNiy

Abstract
Data are presented for hopping conductivity in amorphous hydrogenated 1-yNiy alloys. The behaviour is well described by the form σ = σo [(T o/T)0.5] corresponding to variable-range hopping in a parabolic density of states. However, there is strong quantitative disagreement with the model of Efros and Shklovskii if it is assumed that the hopping is between orbits localized on the impurity atoms. However, a consistent interpretation is obtained if it is assumed that the wavefunctions of the electrons contributing to conduction are extended through clusters of Ni atoms and only localized by longer-range disorder.