Channel switching and magnetoresistance of a metal-SiO₂-Si structure

Abstract

We report a switching of conducting channel and magnetoresistance (MR) in very thin metallic films deposited on Si substrate with native SiO2 surface. The resistance of the metal-oxide-semiconductor (MOS) structure significantly increases when the temperature is lowered to a threshold value Tc of about 250 K. At room temperature the samples exhibit a high conductivity, and a positive MR of about 18%. Below Tc, the resistivity is increased by ~50% and the positive MR disappears. This effect can be explained by the conducting channel switching from the Si electron inversion layer to the upper metallic films when the temperature is decreased. It has also been found that the MR of Cu80Co20-SiO2-Si structure changes sign with the change of temperature, which is correlated to the switching of the conducting channel.