RESUMO
Arrays of vertically aligned Si-nanopillars, with average diameters of 100 nm and 5 µm length, have been prepared by wet chemical etching of crystalline silicon in a special manner. Samples with smooth- and porous-walled nanopillars have been studied. In the case of the latter, Si-nanocrystals, passivated with SiO(x), decorating the surface of the nanopillars are identified by the means of TEM and FTIR. When excited by UV-blue light, the porous-walled Si-nanopillars are found to have a strong broad visible emission band around 1.8 eV with a nearly perfect Gaussian shape, µs luminescence lifetimes, minor emission polarization and a non-monotonic temperature dependence of luminescence. The Si-nanocrystal surface is found to be responsible for the luminescence. The red-shift of the emission maximum and the luminescence quenching induced by oxidation in UV-ozone confirm this assumption. A model of luminescence involving UV photon absorption by Si-nanocrystals with subsequent exciton radiative recombination on defect sites in SiO(x) covering Si-nanocrystals has been proposed. Possible applications of the nanopillar arrays are discussed.
RESUMO
Sputter-deposited aluminum (Al) film surface morphologies were studied with a new nondestructive method that incorporates a high-resolution phase-measuring laser interferometric microscope. Good correlation is obtained between rms roughness and reflectivity for various conditions of temperature and argon gas pressure. It should be noted that the rms roughness is much more sensitive than reflectivity when reflectivity exceeds 90%. A drastic change is observed in the temperature dependence of the rms roughness and the skewness at 200 °C. As a result there are changes in Al grain sizes and surface morphologies based on concomitant scanning electron microscope observations. We found that the rms roughness value depends on the resolution of the objective especially when the Al grain sizes are comparable to the resolution.
