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

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.

Automated summary

The effects of silicon doping on nitrogen-doped diamond-like carbon films were investigated, showing improvements in chemical structure and properties such as reduced cluster formation, increased sp(3) C sites, lower internal stress, and higher optical bandgaps. Additionally, after annealing, Si-N-DLC/p-type Si heterojunctions exhibited rectifying characteristics.