Structural fingerprints in the reflectance anisotropy spectra of InP(001)(2x4) surfaces

The reflectance anisotropy has been calculated from first principles for a series of recently proposed structural models of the InP(001)(2x4) surface. The features of the calculated spectra are related to specific surface bon ding configurations. We find a pronounced negative anisotropy around 1.7 eV linked to transitions between sigma-like In-In bonding states and empty da ngling bonds localized at the surface cations. The strength of that anisotr opy is directly related to the number of In-In bonds at the surface. This e xplains the gradual change of the corresponding measured anisotropy in that energy region, depending on the growth conditions. Positive anisotropies a t higher energies arise from transitions between P-P dimer related states a nd surface resonances. Additionally we find derivativelike features at the energy of the E-1 peak that depend only weakly on the surface structure and stoichiometry. In conjunction with the experimental data, our results indi cate that the (2X4) reconstructed InP(001) surface features In-In bonds alo ng [110] and P-P dimers parallel to [1 (1) over bar 0], respectively. The r elative number of these bonds varies with the growth conditions. [S0163-182 9(99)09003-7].