Effect of the layered structure on the electronic properties of amorphous carbon films on n-Si

Abstract

Amorphous carbon (a-C) films rich in sp3 bonds were grown onto n-type (100) silicon substrates by rf magnetron sputtering. The electrical defects created in the bulk of the carbon films as well as those at the a-C/Si interface during the deposition of the films were characterized electrically. Devices having the metal-insulator-semiconductor structure were fabricated and investigated by means of current-voltage (I-V) and capacitance-voltage (C-V) profiling and admittance spectroscopy. The construction of the films and in particular the presence of layered and bilayer structures was shown to affect the device characteristics. This behavior was attributed to Ar+ ions trapped inside the carbon bulk as well as to charge deficiencies due to the specific growth conditions of the amorphous carbon layers. The density of the interface states was found to depend considerably on the film construction, ranging from 1011 to 1013 eV-1 cm-2. The dynamic behavior of the states was expressed by the relevant time constant, which was calculated to vary from 10-3 to 10-6 s. © 1999 American Institute of Physics.