Study of the Si chemical bonding and semi-conductive behavior of SiCN coatings and their correlation with anti-corrosion properties

Abstract : Amorphous hydrogenated SiCN coatings have been deposited by a PACVD process on M2 steel and silicon substrates. The nitrogen content within the coatings was varied by changing the synthesis conditions. The chemical composition and nature of bonding have been studied by XPS and by X-ray-induced AES. The electrochemical and the semi-conductive properties were evaluated by polarization curves and by using the Mott-Schottky experiments, respectively. When increasin the N/Si ratio, we observed an increase of Si atoms inside the film structure, which were directly bonded to nitrogen. This gradual incorporation of N modified the electrochemical behavior of the films displaying a variation of the density of charge carriers and the semiconductive behavior (p- to n-type). The modified Auger parameter of silicon was used to determine the nature of the silicon chemical bonding inside the [Si-C-N]-based coatings and to predict their corrosion behavior.