Ab initio approach to reconstructions of the InP(111)A surface: Role of hydrogen atoms passivating surface dangling bonds

The reconstructions on InP(111)A surface are systematically investigated using an ab inito-based approach, which incorporates chemical potentials in the gas phase of P(2) and H(2) molecules as functions of temperature and pressure. The calculated surface energy clarifies that the reconstruction depends on both hydrogen and phosphorous chemical potentials. The surface phase diagram as function of temperature and P2 pressure without taking account of passivating H atoms reveals that the stable region for the (2x2) surface with In vacancy is located beyond 450-680 K depending on the pressure, consistent with the experimentally reported temperature range (similar to 670 K). However, the stable temperature range for the (root 3x root 3)R30 degrees surface with P trimer (below 290-430 K) is much lower than the experimental results (similar to 530 K). Considering a reconstruction partially passivated by H atoms, the stable region for the surface with P trimer expands toward higher temperature by similar to 200 K and reasonably agrees with experimentally reported temperature range. Furthermore, comparisons of the calculated scanning tunneling microscopy images for the (root 3x root 3)R30 degrees surface containing P trimer to the experimental data support the plausibility of the surfaces passivated by H atoms. The results obtained thus suggest a possible explanation for the appearance of the (root 3x root 3)R30 degrees reconstruction on InP(111)A surface.