Transport and magnetotransport transition of thin Co films grown on Si

Thin Co films deposited onto p-type Si substrates show a marked transition on their transport properties for temperatures around 250 K. For temperatures higher than 250 K, the planar conduction measured in our samples changes from electronic to hole-like and the film resistance undergoes a clear drop. The transition is also observed by a marked change of the magnetotransport properties of the studied films. This effect can be explained by a conduction channel switching from the upper metallic film to the Si hole inversion layer as we increase the sample temperature. We show that this channel switching may be controlled by applying an external bias voltage to the structure.