Effects of silicon doping on the chemical bonding states and properties of nitrogen-doped diamond-like carbon films by plasma-enhanced chemical vapor deposition

Abstract

• The properties of Si and N doped diamond-like carbon (Si–N–DLC) have been examined. • The internal stress on Si–N–DLC was lower than that on N doped DLC. • The optical bandgap of Si–N–DLC showed an increasing trend with increasing N content. • Si–N–DLC/p-type Si junctions annealed in a vacuum showed rectifying characteristics. We have investigated the effects of silicon (Si) doping on the chemical bonding states and the electrical, optical, and mechanical properties of nitrogen-doped diamond-like carbon (N−DLC) films prepared via plasma-enhanced chemical vapor deposition using hydrogen as a dilution gas. N doping accelerated the formation of clustered sp 2 C in N−DLC films, whereas the clustering was almost suppressed in Si and N doped DLC (Si−N−DLC) films. Sp 3 C sites in the Si–N–DLC films were higher than those in the N–DLC films. For the Si−N−DLC films, sp 3 C-N bonds were preferentially formed compared with the sp 2 C=N bonds. The internal stress on the Si−N−DLC films was lower than that on the N−DLC films. The Si−N−DLC films exhibited higher optical bandgaps than the N−DLC films. As the N 2 flow ratio increased, the optical bandgap of the Si−N−DLC films showed an increasing trend, whereas that of the N−DLC films showed an opposite trend. The current−voltage characteristics of Si−N−DLC/p-type Si heterojunctions were not rectifying; however, after postdeposition annealing, the heterojunctions exhibited rectifying characteristics.