Abstract
Large-scale assembly of individual atoms over smooth surfaces is difficult to achieve. A configuration of an atom reservoir, in which individual atoms can be readily extracted, may successfully address this challenge. In this work, we demonstrate that a liquid gold–silicon alloy established in classical vapor–liquid–solid growth can deposit ordered and three-dimensional rings of isolated gold atoms over silicon nanowire sidewalls. We perform ab initio molecular dynamics simulation and unveil a surprising single atomic gold-catalyzed chemical etching of silicon. Experimental verification of this catalytic process in silicon nanowires yields dopant-dependent, massive and ordered 3D grooves with spacing down to ~5 nm. Finally, we use these grooves as self-labeled and ex situ markers to resolve several complex silicon growths, including the formation of nodes, kinks, scale-like interfaces, and curved backbones.
Highlights
Large-scale assembly of individual atoms over smooth surfaces is difficult to achieve
Given that alloy droplet instability can occur under typical VLS conditions[20,21,22,23,24], we extensively surveyed the surfaces of classical Si nanowires for the potential occurrence of atomic Au patterns over their sidewalls
To enable high-resolution imaging of individual atoms from these relatively thick nanowires and to preserve the sample surface information, we microtomed samples for aberration-corrected scanning transmission electron microscope (STEM) imaging, and used horizontally placed samples made by a focused ion beam system for laser-assisted local-electrode atom-probe tomography (APT) (Fig. 2a)
Summary
Large-scale assembly of individual atoms over smooth surfaces is difficult to achieve. We perform ab initio molecular dynamics simulation and unveil a surprising single atomic gold-catalyzed chemical etching of silicon. Experimental verification of this catalytic process in silicon nanowires yields dopant-dependent, massive and ordered 3D grooves with spacing down to ~5 nm. Sequential, and tunable printing of individual atoms over a large area has not been achieved, but if successful, it could impact fields other than quantum science[2], surface chemistry[4, 5], or single-molecule studies[3]. The Au atoms catalyze the etching of Si nanowires, which subsequently forms massive grooves that are used to probe many crystal growth mechanisms
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