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Ordered arrays of Si nanorods and nanospirals have been produced by ion beam sputter glancing angle deposition of Si on rotating substrates. The substrates were prepatterned with honeycomb and hexagonal-closed-packed arranged Au dots obtained by nanosphere lithography. The effects of template type, substrate rotational speed, height of the artificial Au seeds, and deposition angle θ of the incident flux on the growth of the Si nanostructures is examined. Especially for the deposition of Si on honeycomb templates at different deposition angles, it is shown that the structure of the growing film changes drastically. A continuous film with honeycomblike arranged hillocks on top is deposited at normal incidence. With increased θ, the structure shifts to almost dense films with a mesh of hexagonally arranged pores (θ=70°). Finally, separated rodlike structures with triangular cross section are obtained under glancing angle conditions (θ=85°). In addition, the structural evolution of the glancing angle deposited Si films is compared with oblique angle deposition three-dimensional Monte Carlo simulations. Furthermore, the effects of surface diffusion on the growth of spiral Si nanostructures on nontemplated substrates in experiment and simulation are compared and discussed. [ABSTRACT FROM AUTHOR]

We have recently shown that AlN (0002) (c axis) is tilted abruptly toward the deposition direction as N2 concentration is increased in N2/Ar sputtering gas mixtures. Here, we present a Monte Carlo simulation model to describe the phenomenon of sudden c-axis AlN tilt. The model is based on the assumption that AlN islands with their c axis parallel to substrate normal and AlN islands with tilted c axis coexist at the initial stages of the growth and they can provide the adatoms with different surface mobilities. It is believed that the adatom mobilities are quenched when N2 concentration reaches a certain amount in the reactive sputtering of AlN. Our model further assumes that adatom mobility differences on different islands result in a growth rate difference of the islands. At the initial stages of the growth, AlN islands with tilted c axis grow taller due to the lower adatom mobility on these islands. As they grow taller, they win the competition and stop the further growth of AlN islands with their c axis parallel to substrate normal due to shadowing effect. Monte Carlo simulations revealed that the shadowing effect combined with different adatom mobilities promotes the sudden c-axis tilt in AlN thin films. [ABSTRACT FROM AUTHOR]

A continuum equation for the shadowing growth of individual nanostructures by oblique angle deposition is proposed and numerically integrated. The radius R of rotationally symmetric columns is calculated as a function of height z. Before the radius R saturates at its final value Rsat, column shapes obey the power law R∼zp with the exponent value p∼0.37±0.02. The results are compared to those of an experimental study of Si columns grown on a template (p∼0.39±0.03), and on a flat surface (p∼0.32±0.01). The model additionally predicts that the saturated radius should depend on column separation d as Rsat∼d1.20±.01. This relation implies that the gap between the surfaces of adjacent columns can be optimized by altering the column separation. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We report that tungsten nanocolumns grown by oblique angle sputter deposition develop a quasi-periodic morphology which is not observed for continuous films deposited at normal incidence. The maximum position in power spectral density of the quasi-periodic nanostructures decreases exponentially as a function of thickness. We explain the formation of the quasi-periodic nature by a “shadowing length” concept which plays a similar role to conventional surface diffusion length. Also, we show that the change of the spatial frequency of the periodicity is a result of the elimination of shorter columns due to the shadowing effect during growth. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Studies the surface roughness of a computer disk using atomic force microscopy (AFM) and light scattering. Anisotropic rough surfaces and experimental techniques; AFM measurements; Light scattering measurements.