First Principles Investigation of Interaction between Impurity Atom (Si, Ge, Sn) and Carbon Atom in Diamond-like Carbon System

Xiao-Wei Li, Aiying Wang and Kwang-Ryeol Lee
 

The interaction between impurity atom (Si, Ge, and Sn) and carbon atom in diamond-like carbon (DLC) system was investigated by the simulation method based on density functional theory. The tetrahedral configuration was selected as the calculation model for simplicity. When the bond angle varied in a range of 90-130o from the equivalent state of 109.471o, the distortion energy and the electronic structures including charge density of the highest occupied molecular orbital (HOMO) and partial density of state (PDOS) in the different systems were calculated. The results showed that the addition of Si, Ge and Sn atom into amorphous carbon matrix significantly decreased the distortion energy of the system as the bond angles deviated from the equilibrium one. Moreover, the bonding characteristic between the impurity atom and carbon atom considerably changed depending on the feature of impurity elements. Further studies of the HOMO and PDOS indicated that the electrons tended to be concentrated around the high electronegative carbon atom. These results implied that the electron transfer behavior at the junction of carbon nano-devices could be tailored by the impurity element, and the compressive stress in DLC films could be reduced by the incorporation of Si, Ge and Sn because of the formation of weaker covalent bonds.