Fabrication and characterization of granular Co-SiO2 films and devices

Abstract

The granular Co-SiO2 films with different compositions and thicknesses are prepared by magnetron co-sputtering. The magnetoresistance of the films is measured by a four-probe method. The cobalt contents and film thickness dependence of the magnetoresistance and magnetic coercive properties are studied systematically. Both the MR value and coercive field show a strong dependence on film thickness. The micron-scale and nano-scale granular-in-gap (GIG) devices using Co-SiO2 films are then fabricated by photolithography and electron beam lithography, respectively. The strong electrical field generated in the gap area is found to greatly affect the electron transport process in the device. Generally, at low temperatures, the electron transport is dominated by the electrical-field-induced tunneling. As temperature increases, the dominant transport mechanism gradually changes to thermal-induced tunneling. In order to fabrication the GIG devices, the sputtered and e-beam evaporated NiFe films are also studied.