Channel Switching Effect and Magnetoresistance in Iron Doped Amorphous Carbon Films on Silicon Substrates

Iron doped amorphous carbon films were deposited by pulse laser deposition on n-type silicon substrates. The as-fabricated structure shows a positive magnetoresistance (MR) of 34% at 5 T. Hall measurements show that the carbon film is hole-conducting and therefore a p-n heterojunction forms near the interface so that the current transport channel is transferred from the above carbon films at low temperatures to the Si substrates at high temperatures. The MR measured at high temperatures is attributed to the silicon substrates rather than to an inversion layer in the substrates as reported for many Metal/Insulating Barrier/Si structures.