Conductivity power-law temperature dependence of thin indium oxide films

The conductivity of approximately 50 AA thin effectively two-dimensional indium oxide films was studied as a function of temperature around and below the cross-over to strong localisation, with a fine tuning of the room-temperature sheet resistance. When the latter is in an extremely narrow range around 50 k Omega/Square Operator , a conductivity proportional to T over a broad range was obtained. The results were interpreted using a hopping mechanism, suggested by Gogolin, Mel'nikov and Rashba, (1975) and by Thouless (1977). General conditions to obtain this power-law behaviour in any dimension were formulated.