arXiv subjects

S. Pochon

Publications and source records attributed to S. Pochon.

3 recordsLinked to original sources

arXiv2003

Controlling the coexistence of structural phases and the optical properties of gallium nanoparticles with optical excitation

We have observed reversible structural transformations, induced by optical excitation at 1.55 micrometer, between the beta, gamma and liquid phases of gallium in self-assembled gallium nanoparticles, with a narrow size distribution around 50 nm, on the tip of an optical fiber. Only a few tens of nanowatts of optical excitation per particle are required to control the transformations, which take the form of a dynamic phase coexistence and are accompanied by substantial changes in the optical properties of the nanoparticle film. The time needed to achieve phase equilibrium is in the microsecond range, and increases critically at the transition temperature.

cond-mat↗

arXiv2003

Phase coexistence in Gallium nanoparticles controlled by electron excitation

In Gallium nanoparticles of 100 nm in diameter grown on the tip of an optical fiber from an atomic beam we observed equilibrium coexistence of gamma, beta and liquid structural phases that can be controlled by e-beam excitation in a highly reversible and reproducible fashion. With 2 keV electrons only 1 pJ of excitation energy per nanoparticle is needed to exercise control, with the equilibrium phase achieved in less than a few tenths of a microsecond. The transformations between coexisting phases are accompanied by a continuous change in the nanoparticle film's reflectivity.

cond-mat↗

arXiv2001

Gallium nanoparticles grow where light is

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.

physics.optics↗