Comparative EPR study of hydrogenated and unhydrogenated amorphous silicon carbide thin films

Abstract

In this work, electron paramagnetic resonance (EPR) is used to study paramagnetic centers in stoichiometric hydrogenated a-SiC:H synthesized by plasma enhanced chemical vapor deposition (PECVD) and unhydrogenated a-SiC grown by pulsed laser deposition. While the spin density of the a-SiC films was determined to be of the order of 10 20 spins/cm 3, it was found to be more than one order of magnitude lower (10 19 spins/cm 3) for the as-deposited a-SiC:H films and decreases to less than 10 17 spins/cm 3 upon annealing at 650 °C. For both types of films, the dominant paramagnetic centers in the films are carbon related defects, as deduced from the g-value of the EPR signal. The PLD a-SiC films have a symmetric exchange narrowed Lorentzian EPR line that indicates some clustering of the spins. For a-SiC:H films, the EPR shows some asymmetry that is probably due to the presence of silicon related defects in the layers. No evidence of spin clustering was found for a-SiC:H and the EPR linewidth is most likely determined by dipolar interaction and some unresolved hydrogen hyperfine structure for the as-deposited and annealed a-SiC:H films, respectively. The temperature dependence of the EPR linewidth for both types of films and the power saturation behavior of the EPR signal are also presented and discussed.