Structure and magneto-electrical properties of Fe-C films prepared by magnetron sputtering

Fe-doped amorphous FexC1−x granular films were prepared on n-Si (100) substrates by d.c. magnetron sputtering. The structural properties of FexC1−x films were investigated by X-ray diffraction (XRD), atomic force microscope (AFM) and Raman spectroscopy. The results show that the iron and carbon of as-deposited films are in amorphous state, and the FexC1−x films are diamond-like carbon (DLC) films. After doping iron into the DLC films, a smooth surface morphology of the FexC1−x films has been obtained with the surface roughness Ra of about 0.231 nm for x=18at%. The FexC1−x films have good soft magnetic properties with the coercivity of approximately 20 Oe. A high positive magnetoresistance (MR) up to 93% with x=1at% was observed in a FexC1−x granular film at 300 K. The resistance characteristic of Fe-C films is changed at about 230 K and the positive MR effect can be understood by the p-n heterojunction theory.