Low energy electron microscopy study of In on Si(111)

Abstract

The structural phase transitions in the multiphase system indium (In) on Si(111) are studied as a function of coverage at different temperatures between −100 and 550 °C by low energy electron microscopy (LEEM) and low energy electron diffraction (LEED). All phase transitions observed with increasing In coverage are first order. Nucleation of a new phase starts only after the previous phase is completed. At high temperatures only a disordered monolayer with high atomic density forms. When In is deposited at room temperature on a (√3×√3)-R30°–In surface four new phases are observed: a (2×1), a near coincidence (1.5√3×1.5√3), a “(1×1)-R30°” and a (6×6) phase. At room temperature and up at least to 400 °C a double layer forms. Below 120 °C this layer is compressed and ordered in two coexisting structures, (√7×√3) and “(1×1)-R30°”. Above 120 °C it shows a (1×1) LEED pattern, which is attributed to a disordered layer on the Si(111)-(1×1) surface. A third monolayer with the packing density of a slightly compressed In(111) plane is unstable at room temperature against formation of three-dimensional crystals but becomes stable during growth at temperatures below about −80 °C. Three-dimensional crystals grow at room temperature on the double layer in the Stranski–Krastanov mode. These crystals are primarily (100)-oriented and are bounded by the equilibrium planes known from bulk crystals, including the reconstructed (100) surface, which is no longer reconstructed above 120 °C.