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

Amorphous carbon (a-C) films rich in sp(3) bonds were grown onto n-type (10 0) silicon substrates by rf magnetron sputtering. The electrical defects cr eated in the bulk of the carbon films as well as those at the a-C/Si interf ace during the deposition of the films were characterized electrically. Dev ices 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 th e specific growth conditions of the amorphous carbon layers. The density of the interface states was found to depend considerably on the film construc tion, ranging from 10(11) to 10(13) eV(-1) cm(-2). The dynamic behavior of the states was expressed by the relevant time constant, which was calculate d to vary from 10(-3) to 10(-6) s. (C) 1999 American Institute of Physics. [S0021-8979(99)02420-2].