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We developed a growth technique that improves the crystallinity and optical properties (photoluminescence intensity and lifetime) of Er-doped Gd2O3 (Er:Gd2O3) on a Si(111) substrate. Deposition of thin (7.5 Å thick) Gd metal on the SiOx-covered surface of the Si(111) substrate prior to the growth of Er:Gd2O3, and the successive, thermally-induced redox reaction gives rise to the solid-phase epitaxy of GdOx on Si, which protects Si from unintentional oxidation and fosters the epitaxial growth of Er:Gd2O3 on it; i.e., GdOx serves as a protection and seed (bifunctional) layer. This technique is promising for developing high-performance optical devices using high-quality rare-earth oxide films grown on Si substrates. [ABSTRACT FROM AUTHOR]

We grow single crystal erbium-oxide (Er2O3) epitaxially on a Si (111) substrate by using molecular beam epitaxy and investigate the population dynamics in Er3+ ions for the coherent manipulation of the population in Er2O3. Sharp and discrete Stark energy levels of the 4I13/2 manifold as small as 200 μeV are observed with inhomogeneous broadening caused by the uniform crystal field of the epitaxial Er2O3. We also experimentally determine the time constant of the resonant population transfer between spatially distant Er3+-ion sites, which is limited to the manipulation time of the population in the Er2O3 crystals. Using selective excitation of the Stark level in the 4I13/2 manifold, we obtain the energy transfer times between spatially distant Er3+ ions, and they are about 2 μs between sites whose crystallographic symmetry is different and 10 μs between sites whose symmetry is the same. [ABSTRACT FROM AUTHOR]

Based on scanning tunneling microscopy observations, we have investigated the formation and self-stabilization of Ge nanowires on Si(1 1 3) during Ge deposition. Under zero Ge flux, we observed a shape transition from nanowires to dot-like islands by annealing at 430°C, which is a favorable temperature for nanowire formation during deposition. The nanowires are, therefore, metastable and are formed under a kinetically limited growth condition. We find that the strain of the nanowire is relaxed anisotropically. During growth the nanowire shape is effectively self-stabilizing, which leads to elongated growth of the islands. [Copyright &y& Elsevier]