THE ELECTRONIC-STRUCTURE OF DIAMOND-LIKE AMORPHOUS-CARBON

The electronic structure of diamond-like amorphous carbon is investigated using a tight-binding molecular dynamics method. The study shows that bonding and antibonding of pi-states associated with pairs and quartets of threefold 'defected atoms' embedded in the fourfold matrix yield a band gap of about 2 eV as observed in optical absorption experiments. These states are in general very localized. However, coupling between the threefold 'defects' can produce delocalized states near the band gap, which is essential for electronic conductivity in the material.