Effect of annealing ambient on anisotropic retraction of film edges during solid-state dewetting of thin single crystal films

Abstract

During solid-state dewetting of thin single crystal films, film edges retract at a rate that is strongly dependent on their crystallographic orientations. Edges with kinetically stable in-plane orientations remain straight as they retract, while those with other in-plane orientations develop in-plane facets as they retract. Kinetically stable edges have retraction rates that are lower than edges with other orientations and thus determine the shape of the natural holes that form during solid-state dewetting. In this paper, measurements of the retraction rates of kinetically stable edges for single crystal (110) and (100) Ni films on MgO are presented. Relative retraction rates of kinetically stable edges with different crystallographic orientations are observed to change under different annealing conditions, and this accordingly changes the initial shapes of growing holes. The surfaces of (110) and (100) films were also characterized using low energy electron diffraction, and different surface reconstructions were observed under different ambient conditions. The observed surface structures were found to correlate with the observed changes in the relative retraction rates of the kinetically stable edges.

Dewetting mechanisms and their exploitation for the large-scale fabrication of advanced nanophotonic systems

“…The edge alignment along the particular directions can be understood in terms of the surface energy anisotropy of the film material, and it has also been demonstrated that they can be tuned by varying the annealing ambient [78]. It has been suggested that surface reconstruction by oxygen adsorption can also affect the hole shapes in Ni (100) and Ni (110) films as indicated by low-energy electron diffraction analysis [79]. Because of this shape anisotropy in nucleated holes, single-crystal films dewet into more regular morphologies compared to polycrystalline or liquid films.…”

Fabrication of Platinum Nanoparticles with Different Morphologies by Thermal Dewetting in the Presence of Residual Oxygen and Their Optical Properties

“…32 Differences in thermal dewetting atmosphere have been shown to influence the dewetting behavior and the morphology evolution of metal thin films. 33,36,37 Particularly, in their study on the effect of oxygen adsorption on the morphological evolution of Ag films on Si substrates, Ye et al 35 have shown that oxygen enhances the dewetting rate of Ag thin films which they attribute to the decrease in the activation barrier for the surface diffusion of Ag atoms due to oxygen adsorption. With the reduced activation energy, surface diffusion could take place more easily, leading to a faster dewetting process, as thermal dewetting is a solid-state dewetting process driven by surface diffusion.…”

“…Geissler et al reported the effect of H 2 pressure on the size of Ni NPs formed during thermal dewetting of Ni films on SiO 2 (25 nm)/Si substrates, where the NP size was seen to increase along with a decrease in the NP number density when the H 2 pressure increased. The effect of annealing ambient on the equilibrium crystal shape of Ni nanoparticles formed during solid-state thermal dewetting has also been reported. − Adsorption of oxygen and hydrogen on metal surfaces has a significant impact on both the surface energy anisotropy and the surface diffusion anisotropy, leading to anisotropic retraction of film edges during thermal annealing and eventually the equilibrium crystal shape. The effect of ambient conditions on the size and shape of Pt NPs in the solid-state thermal dewetting of Pt thin films has been much less studied.…”