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A novel method has been optimized so that adhesion layers are no longer needed to reliably deposit patterned gold structures on amorphous substrates. Using this technique allows for the fabrication of amorphous oxide templates known as micro-crucibles, which confine a vapor-liquid-solid (VLS) catalyst of nominally pure gold to a specific geometry. Within these confined templates of amorphous materials, faceted silicon crystals have been grown laterally. The novel deposition technique, which enables the nominally pure gold catalyst, involves the undercutting of an initial chromium adhesion layer. Using electron backscatter diffraction it was found that silicon nucleated in these micro-crucibles were 30% single crystals, 45% potentially twinned crystals and 25% polycrystals for the experimental conditions used. Single, potentially twinned, and polycrystals all had an aversion to growth with the {1 0 0} surface parallel to the amorphous substrate. Closer analysis of grain boundaries of potentially twinned and polycrystalline samples revealed that the overwhelming majority of them were of the 60° ∑3 coherent twin boundary type. The large amount of coherent twin boundaries present in the grown, two-dimensional silicon crystals suggest that lateral VLS growth occurs very close to thermodynamic equilibrium. It is suggested that free energy fluctuations during growth or cooling, and impurities were the causes for this twinning. [ABSTRACT FROM AUTHOR]

The mechanical resonance of laterally grown silicon nanowires measured by an optical interferometric technique is reported. The lengths and diameters of the nanowires ranged from L=2 to 20 μm and D=39 to 400 nm, respectively. The wires showed resonant frequencies in the f0=1–12 MHz range and resonant quality factors Q at low pressure ranging from Q=5000 to Q=25 000. The dependence of resonant frequency on the ratio of diameter to length squared, D/L2, yielded a ratio of E/ρ=9400±450 m/s. Assuming a density of ρ=2330 kg/m3, this experimental result yields an experimental Young modulus of E=205±10 GPa, consistent with that of a bulk silicon. As the wires were cooled from T=270 K to T=77 K, a 0.35% increase of resonant frequency was observed. This increase of resonant frequency with cooling resulted from a change in Young’s modulus and from the thermal contraction of silicon. The quality factor did not vary significantly from P=10-4 to 102 Torr, suggesting that viscous damping does not dominate the dissipative processes in this pressure range. Although viscous damping became important above P=102 Torr, relatively high quality factors of Q=7000 were still observed at atmospheric pressure. [ABSTRACT FROM AUTHOR]

Relaxation of compressed InP and InGaAs at different strains and temperatures is examined in this study. For example, different compressive strain states of InP can be attained by depositing InP on an InxGa1-xAs graded buffer with different compositions, x. In slightly strained elemental and compound semiconductor films, including InP and InGaAs, relaxation occurs via the primary-slip system, a/2<110>{111}, where glide takes place on {111}-type planes. At high lattice mismatches, Lomer edge dislocations are the predominant form of relaxation. In this work at intermediate lattice-mismatch strains, relaxation occurred via the secondary, a/2<110>{110}, slip system in InP and InGaAs. For these strains above a critical strain of about 0.0085, both the primary- and secondary-slip systems are active evident by cross slip between these two slip systems. The extent of relaxation via the primary- or secondary-slip system was found to be dependant on growth temperature. Relaxation via the secondary-slip system, when it was active, increased as the temperature decreased and we found a 1.5 eV difference between the activation energy for glide via the primary- and secondary-slip systems. [ABSTRACT FROM AUTHOR]

Gold nanoparticles from commercially available colloids were deposited onto a hydrogen-terminated silicon substrate without the use of a polyelectrolyte linker by the addition of HF acid. The deposition density was shown to be controlled over three orders of magnitude by varying the colloid concentration, and finer control is achieved by varying the deposition time. In order to minimise agglomeration, however, we show that deposition times should be minimised since nanoparticle agglomeration increases rapidly over the first 2 min after the addition of HF. To increase nanoparticle density without increasing agglomeration, we show that successive depositions of short times linearly increase the deposition density without increasing the agglomeration of nanoparticles., (Copyright © 2011 Elsevier Inc. All rights reserved.)