First-principles study of silicon bulk and nanowire (111) surfaces terminated with trihydrides: Symmetric, rotated, and tilted

Abstract

We report the structural stability and electronic properties of silicon bulk and nanowire ͑111͒ surfaces terminated with symmetric, rotated, and tilted trihydrides based on first-principles calculations. For the bulk surfaces, the one with a tilted trihydride was found to be the most stable with the rotated one next to it in both total-energy calculations and molecular-dynamics simulations. A similar stability trend was further obtained for ͗110͘ silicon nanowires. These stability characteristics were shown to be sensitively determined by the surface hydrogen chemical-potential changes. Interestingly, the tilting of the surface trihydride from a symmetric configuration resulted in a noticeable blueshift in the band gap for the Si nanowire, opening up the possibility that the electronic properties can be tuned. The above effects of surface terminations are generic and apply as well to similar materials composed of, for instance, Ge and C, as also demonstrated.