Anomalous conductivity and positive magnetoresistance in FeSi-SiO2-Si structures in the vicinity of a resistive transition

Electrical and magnetic transport properties of FeSi-SiO2-Si junctions fabricated by depositing FeSi thin films on silicon substrates with the native oxide layer have been investigated. Near room temperature the carriers tunneled across the interface to the substrate with low resistance. With a decreasing temperature, the junction resistance increased more than three orders of magnitude near 270 K, which switched the current path to the film. The transition characteristics depend on the conductivity of the silicon substrate. A positive magnetoresistance that peaked near the transition temperature was observed. Similar behavior was seen for CoSi films while TiSi films did not show a transition in resistance.