ELECTRICAL-CONDUCTION IN THE INSULATING REGION OF GRANULAR TIN

The temperature dependence of the conductivity of granular tin is anal ysed. Variable range-hopping (VRH) conduction is observed at low tempe ratures. The type of the VRH changes from a Mott to an ES (Efros-Shklo vskii) one as the material becomes more localized. Above the VRH regio n, power-law temperature dependences are observed. A scaling theory of localization is used to obtain a possible explanation. Interestingly, electron-electron inelastic scattering is dominant for the samples in which ES-type VRH appears at low temperatures.