Electrical conductivity of nanocrystalline nonstoichiometric tin dioxide films near the metal-insulator transition

Abstract

The temperature dependence of conductivity σ(T) of nonstoichiometric tin dioxide films were studied in the temperature range 4-300 K. The films were fabricated by reactive DC magnetron sputtering with following 2-stage temperature annealing. Samples are characterized by high electron concentration (more than 10^20 cm^-3) and a high degree of disorder. Several methods used to distinguish between metallic or insulating types of conductivity were employed to interpret experimental σ(T) dependences. These methods give opposite conclusions. Model of polaron transport in metallic systems with strong lattice disorder stimulating dynamic process of electron-phonon coupling was proposed for our samples in order to settle the discrepancies.