First-principles study on the dissociation of As₂ on BaSi₂ (100) surface

This study investigates the dissociation behavior of arsenic dimers (As₂) on the BaSi₂ (100) surface using first-principles calculations, aiming to evaluate the possibility of As2 dissociation on the surface during growth. We explored multiple dissociation configurations and reaction pathways using nudged elastic band (NEB) calculations to determine the minimum energy paths and corresponding energy barriers. Four stable dissociated states were identified, most of which exhibit greater thermodynamic stability than the initial adsorbed configuration. The calculated energy barriers range from 0.19 to 1.05 eV. Further analysis reveals that As₂ dissociation is significantly limited under typical growth temperatures (500–750 °C), supporting the hypothesis that incomplete dissociation contributes to the formation of donor-deactivating As–As defect complexes. These findings provide insight into the doping limitations of BaSi₂ and suggest that optimizing growth conditions may enhance donor activation efficiency.