Thin films of a-Sn were epitaxially grown on InSb(111)A and InSb(111)Bsubstrates at room temperature. %'e studied growth modes and phase transitions of the films by using refiection high-energy electron diffraction and Auger electron spectroscopy. The films on InSb(111)A grew in biatomic layer-bylayer modes. Characteristic growth features for Sn/InSb(111)B were due to the segregation of Sb to the a-Sn film surface. Thus, we used the Sn/InSb(111) A system to examine the stability of the films as a function of Sn coverage. The as-grown film surfaces changed irreversibly from the (3 X 3) structure, to the (2 X 2), and, subsequently, to the (1 X 1) structure, and finally to melting while going to elevated temperatures. The transition temperatures for the thinner film were more than 10'C higher than for the thicker film. Finally, to study the role of an interface in the stable growth of a-Sn on InSb(111)A, we performed discrete variational Xa cluster calculations.
We grew coherent Ge islands on Si(113) substrates by molecular beam epitaxy. Atomic force microscopy and reflection high energy electron diffraction were used to examine surface morphology as a function of Ge coverage and growth temperature. The as-grown coherent islands were shaped like wires and formed dense arrays over the entire surface. The islands bounded by {519} facets were elongated in the [332̄] direction and were linearly ordered across steps. The wire-shaped islands formed when Ge coverage was 5–8 monolayers and the growth temperature was 400–500 °C. Cross-sectional transmission electron microscope images confirm that the Ge islands are coherently grown on the Si substrates. The anisotropic shape of the Ge islands was due to an anisotropic strain relief mechanism on Si(113), which had been theoretically predicted. Our findings suggest that the coherent island formation of Ge on Si(113) may be a possible method to fabricate self-assembled Ge nanowires.
We apply Gans theory to fit the absorption spectra of gold nanorods with aspect ratios R e 2.5 in solution using both the longitudinal and transversal surface plasmon resonance absorption peaks and the dielectric constant of the medium, m , as a fitting parameter. By fitting the broadened absorption peaks using the absorption spectra of a set of nanorods with a range of aspect ratios, we determine the size distribution of the nanorods in solution. The optimum value of m ) 2.1 ( 0.1 is substantially higher than the dielectric constant of the solvent ( m,water ) 1.77), which is most likely due to a change in the effective dielectric constant in the vicinity of the nanorods. The validity of our method is confirmed by comparing the calculated size distributions with transmission electron microscope images, and we obtain a good agreement between the experiments and our calculations. Furthermore, several other recent experimental results are compared with our fitting method, and we find that the discrepancy between Gans theory and those experimental results can be explained by using higher values of m .
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