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

We report a switching of conducting channel and magnetoresistance (MR) in v ery thin metallic films deposited on Si substrate with native SiO2, surface . The resistance of the metal-oxide-semiconductor (MOS) structure significa ntly increases when the temperature is lowered to a threshold value T-c of about 250 K. At room temperature the samples exhibit a high conductivity, a nd a positive MR of about 18%. Below T-c, the resistivity is increased by s imilar to 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 be en found that the MR of Cu80Co20-SiO2-Si structure changes sign with the ch ange of temperature, which is correlated to the switching of the conducting channel.