RESONANT INVERSE PHOTOEMISSION OF SB MULTILAYERS ON GAAS(110) AND INP(110) SURFACES

The coverage- and structure-dependent empty electronic states of Sb multilayers on nearly unrelaxed GaAs(110) and relaxed InP(110) have been investigated using photoemission (IPES) and low energy electron diffraction. Two significant Sb-derived empty states, termed features A and B, are used to characterize the evolution of ordered, metastable Sb multilayers and the ordered first monolayer. Feature A appears approximately 0.30 and approximately 0.35 eV above E(F) for ordered metastable Sb multilayers on p-GaAs(110) and p-InP(110), respectively, while feature B appears at 2.0 eV for 1 ML of ordered Sb. Feature A resonates for photon energies of IPES near h-omega-p = 15.9 eV because radiative decay of a plasmon within the Sb film provides a decay channel that competes with the inverse photoemission channel. This resonance occurs for thicknesses greater than approximately 3.5 ML for GaAs(110) and approximately 2 ML for InP(110) for overlayers annealed at 475 K following Sb growth at 300 K. Structural studies reveal that the resonance features of IPES are correlated with metastable structures of the Sb layers. Very gradual relief of strained-layer structures, coherent with (110) surfaces, may contribute to the existence of metastable phases for coverages below approximately 10 ML. For Sb/GaAs(110), the metastable structures consist of long-range-ordered (110) domains with Sb crystallites between them. For Sb/InP(110), the metastable structures may be associated with a fairly continuous, periodic distribution of atomically corrugated (110) domains along [001], and the plane defined by the Sb zig-zag chains is not parallel to the unrelaxed (110) surface. These metastable structures may provide various coupling conditions for the momenta of the photon and the electron-excited Sb plasmons.