OBSERVATION OF CONDUCTANCE FLUCTUATIONS IN LARGE IN2O3-X FILMS

We have measured the magnetoconductance in the hopping regime of two thin films of crystalline In2O3-x. The films are 18 nm thick and have large (macroscopic) areas 2×2 and 1×0.3 mm2. We observe a large positive magnetoconductance and reproducible conductance fluctuations. The conductance fluctuations are easy to observe below 100 mK and their amplitude is consistent with simple ensemble averaging of phase-coherent regions. When the field is rotated into the plane of the film, the field scale for the conductance fluctuations increases by a factor of 2 suggesting that they are partly due to orbital effects. © 1990 The American Physical Society.