Gallium nanoparticles grow where light is

TL;DR

This paper demonstrates that light can non-thermally influence the self-assembly of gallium nanoparticles, enabling controlled formation at low light intensities through electronic excitation rather than thermal effects.

Contribution

It reveals a novel light-induced mechanism for nanoparticle formation, expanding understanding of light-matter interactions in nanoparticle self-assembly processes.

Findings

Light influences gallium nanoparticle formation without thermal effects.

Low light intensities induce non-thermal atomic desorption.

Nanoparticles form with a narrow size distribution under illumination.

Abstract

The study of metallic nanoparticles has a long tradition in linear and nonlinear optics [1], with current emphasis on the ultrafast dynamics, size, shape and collective effects in their optical response [2-6]. Nanoparticles also represent the ultimate confined geometry:high surface-to-volume ratios lead to local field enhancements and a range of dramatic modifications of the material's properties and phase diagram [7-9]. Confined gallium has become a subject of special interest as the light-induced structural phase transition recently observed in gallium films [10, 11] has allowed for the demonstration of all-optical switching devices that operate at low laser power [12]. Spontaneous self-assembly has been the main approach to the preparation of nanoparticles (for a review see 13). Here we report that light can dramatically influence the nanoparticle self-assembly process: illumination of a substrate exposed to a beam of gallium atoms results in the formation of nanoparticles with a relatively narrow size distribution. Very low light intensities, below the threshold for thermally-induced evaporation, exert considerable control over nanoparticle formation through non-thermal atomic desorption induced by electronic excitation.