Simulation of carbon containing complexes at silicon-silicon grain boundaries in cluster approximation

The transformation of the “core” for the tilt Σ5 θ=37° [001]/(130) grain boundary (GB) in polycrystalline silicon due to incorporation of carbon atoms is studied with a method of molecular orbital-linear combinations of atomic orbital (MO LCAO) in PM3 approximation. Insertion of carbon atoms into 5- or 7-fold interstitial positions at GB “core” formed donor-like complexes which are composed of combined Si2C, Si3C or Si4C configurations depending on number x of incorporated C-atoms. Energy levels of such complexes are shifted to the bottom of the conductive band from EC-0.536 eV to EC-0.043 eV with increasing x from 1 to 4.