Abstract
Abstract By the use of comparably low etching-rate of uniform size Ge QDs as mask, a method was developed to fabricate pyramidal nanodots with excellent uniformity over large area, containing Si-Ge superlattice structure. Photoluminescence measurements reveal that Si-Ge superlattice nanodots exhibit about ten fold enhancement in intensity over conventional Si-Ge superlattice heterostructure, which may lead to applications in optoelectronic devices. The enhancement in PL is attributed to quantum confinement effects. An additional incentive is that the method is compatible with the existing Si/SiGe-based integration technology. Taking advantage of comparably low etching-rate for Si and uniform size of self-assembled Ge QDs/Si spacer multilayers, a method has been developed to fabricate multilayered Ge@silica nanolenses with excellent uniformity over large area. The samples with Ge@silica nanolens stacks exhibited a reflectivity with an increase of about 77 % around 1.5 □m over conventional self-assembled Ge QDs/Si spacer multilayers. In addition, it showed an emission peak between 1.5 and 1.55 □m in photoluminescence spectrum. The combination of photoluminescence and reflectance properties of multilayered Ge@silica nanolenses promises applications as a Si-compatible photodetector material for telecommunication. NiSi2/SiGe-based nanotubes have been fabricated on the Si surfaces by precise transformations from two-dimensional structures to three-dimensional objects. By using the strain in a pair of lattice-mismatched epitaxy layers, a method was developed to create nanotube structure released from a substrate. A new structure combining semiconductor (SiGe) and metallic silicide (NiSi2) into a single nanotube structure was achieved by employing strained p+-Si/Si0.7Ge0.3 substrates. SiGe/metal silicide bilayer nanotubes with a wide range of properties are appropriate for many applications since semiconductor epi-layers possess remarkable control over material composition, doping concentration, and layer thicknesses. Long-range ordered heteroepitaxial □-FeSi2 nanodots were grown on strained Si/Si0.8Ge0.2 (001) substrates by solid phase epitaxy method. Ordering was observed on surfaces of strained Si/Si0.8Ge0.2 substrate where the □-FeSi2 nanodots appear to be confined to one-dimensional array along <110> direction. It is shown that dislocation slip originating from compositionally graded Si1-xGex layers can produce local surface-strain variation that can be used for the fabrication of epitaxial □-FeSi2 nanostructures on the surface of strained Si/Si0.8Ge0.2 substrate. In addition, a photoluminescence peak at 840meV that contributes from □-FeSi2 nanodots is measured at 11 K. Consequently, the fabrication procedure of □-FeSi2 nanodots allows the possibility of combining optoelectronic devices with SiGe/Si-based circuits in the same integrated circuit. Detailed studies of the transformation from branched Si nanowires into Ni2Si nanowires structures demonstrate that the property of dominant diffusing species of Ni atoms and the diffusion-controlled growth mechanism in nanoscale Ni/Si system. The atomically sharp interface of the Ni2Si/NiSi produced in the nanowire heterostructure has revealed the epitaxial relationship in the nanometer-scale transformation process. The investigation of the transformation of silicon nanobelts into nickel silicide nanobelts on the temperature rise is achieved. The activation energy for the growth of Ni31Si12 nanobelts was obtained (1.06 eV)from an Arrhenius plot.