Electrical Properties and Magnetoresistance of Nanogranular $SnO_2$ Films

Magnetotransport properties of the nanogranular $SnO_2$ films were invesigated. Non-linear current-voltage (I-V) characteristics were observed at low temperatures. The temperature dependence of the resistance and non-ohmic I-V curves can be well approximated by fluctuation-induced tunnelling model, indicating importance of the contacts barriers between $SnO_2$ grains. Magnetoresistance was measured within temperature range 2-15.3 K and could be consistent with the variable-range hopping conduction mechanism due to existence of localized states on the surface of $SnO_2$ grains.