Abnormal current-voltage characteristics and metal-insulator transition of amorphous Fe-doped carbon films on Si substrates

Amorphous Fe0.05-C0.95 films have been deposited on n-type Si substrates using direct current magnetron sputtering. The structure and electrical properties of the films/Si are investigated. The film/Si deposited at room temperature exhibits abnormal current-voltage (I-V) characteristics, whose current increases slowly at first, and then increases to a very large value when the voltage reaches a threshold. However, the I-V curves of the film on Si substrate deposited at 200 °C are almost linear. In addition, the temperature dependence of the resistance of the film/Si shows a metal-insulator transition and the transition temperature can be hugely modulated by increasing the external bias voltage. Finally, we propose a possible model to interpret the abnormal electrical properties of the film/Si.