The temperature dependence of electrical conductivity of rf-sputtered amorphous Ge, Si, and Ge-Si films as functions of annealing temperature and time have been investigated for $350\gtrsim T\gtrsim 77$ K. Annealing shifts the hopping region to lower temperatures. We find that reasonable values of Mott's parameters are obtained only for properly annealed specimens in the true hopping-conduction region.

• Received 30 July 1973

DOI:https://doi.org/10.1103/PhysRevLett.31.1000