What is it about?
Surfaces are made by atomically flat terraces separated by one-atom-high steps. In this article we have investigated the stability of thin films of silicon (111) on silica against dewetting. In particular we have verified the role of the step-down orientation direction on the stabilities of thin films.
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Why is it important?
We have experimentally shown that the break up of unstable thin films in contact with a substrate depends on the step-up/step-down directions of the film surface. In a thin film of silicon with orientation (111) in contact with silica - SOI(111) -, we see that the dewetting start with the formation of hexagonal holes with uneven edges. Silicon accumulates in a rim around the void, and the rim grows in height layer by layer before the formation of branches or dewetting fingers. Dewetting takes place faster in the step-down direction, and Kinetic Monte Carlo simulations confirm our observations, explaining the atomic details of rim and finger formation. Initially, a new rim layer isn't needed; atoms leaving the hole build up the upper surface. Only when the distance between the hole edge and a surface step increases, a new rim layer forms around he hole. We have also shown that in the first dewetting stages the thickness of the rim proceeds by nucleation and growth of a new atomic layer.
Perspectives
When I started thinking about the first draft of this article, I thought it would have been a conventional article on the instability of silicon films on insulator. Discussing with my colleagues, I realized that there were additional investigations to make it much more interesting. After these investigations, I think the article has gained much. I am actually very happy of the final results, as we have put in evidence the effect of a parameter that is often overlooked by most researchers (i.e. the surface morphology).
Stefano Curiotto
Centre National de la Recherche Scientifique
Read the Original
This page is a summary of: Rim nucleation and step-train orientation effects in SOI(111) dewetting, Surfaces and Interfaces, February 2024, Elsevier,
DOI: 10.1016/j.surfin.2024.103912.
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