Thermodynamic phase diagram for hydrogen on polar InP(111)B surfaces

Thermodynamic stability of hydrogenated polar InP(111)B surfaces is systematically studied by performing first-principles density functional calculations. Employing a thermodynamic approach, the hydrogen chemical potential is considered as functions of temperature and pressure. The calculated Gibbs free energies demonstrate that the surface structures of InP(111)B strongly depend on growth condition and surface compositions. The (2×2) surfaces with 3PH2+PH3, 3H+PH3, 3H, and P trimer, and the (3×3) surface with In adatom are stable phases under different chemical potentials of P and H, respectively. Moreover, our calculations suggest that the ideal surface and most of (3×3) surfaces are just metastable due to their deviation from electron counting rule. The calculated surface phase diagrams as the functions of temperature and pressure of H2 reveal that the (2×2) surface with P trimer is stable under the experimental growth condition (550–800 K). Once the samples are cooled down in a H-rich ambient, the hydrogenated InP(111)B surfaces are more favorable.