Controlling phase coexistence and optical properties of gallium nanoparticles
Controlling phase coexistence and optical properties of gallium nanoparticles
We discovered that a low-power laser light can dramatically influence and regulate nanoparticles self-assembly process: presence of laser light pulses of 1 μs duration and efficient cooling of a substrate exposed to a beam of gallium atoms are the conditions required for formation of gallium nanoparticles with a relatively narrow size distribution centred at ~50 nm. We argue that the formation of gallium nanoparticles is influenced by very low intensity light through nonthermal laser-induced desorption and or adsorption-suppression during the growth process.
Using these self-assembled gallium nanoparticles film with a narrow size distribution, we discovered that low intensity light can stimulate reversible solid-solid and solid-liquid phase transitions when the sample temperature approaches the critical value. The transformations belong to a novel class of surface-driven excitation-induced phase transitions.
In gallium nanoparticles grown on the tip of an optical fibre, we discovered that electron-beam excitation allows control of the equilibrium coexistence of γ, β and liquid structural phases in a highly reversible and reproducible fashion. With 2 KeV electron beam, 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 second. The transformations between coexisting phases are accompanied by a continuous change in the nanoparticles film’s reflectivity. The transformations are believed to belong to surface-driven excitation-induced phase transitions.
Experimental results suggests that both thermal and non-thermal mechanisms contribute to the effect observed in both laser and electron beam excitation. Calculations of gallium nanoparticles films optical properties support the strength of the model.
University of Southampton
2004
Pochon, Sebastien Claude
(2004)
Controlling phase coexistence and optical properties of gallium nanoparticles.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
We discovered that a low-power laser light can dramatically influence and regulate nanoparticles self-assembly process: presence of laser light pulses of 1 μs duration and efficient cooling of a substrate exposed to a beam of gallium atoms are the conditions required for formation of gallium nanoparticles with a relatively narrow size distribution centred at ~50 nm. We argue that the formation of gallium nanoparticles is influenced by very low intensity light through nonthermal laser-induced desorption and or adsorption-suppression during the growth process.
Using these self-assembled gallium nanoparticles film with a narrow size distribution, we discovered that low intensity light can stimulate reversible solid-solid and solid-liquid phase transitions when the sample temperature approaches the critical value. The transformations belong to a novel class of surface-driven excitation-induced phase transitions.
In gallium nanoparticles grown on the tip of an optical fibre, we discovered that electron-beam excitation allows control of the equilibrium coexistence of γ, β and liquid structural phases in a highly reversible and reproducible fashion. With 2 KeV electron beam, 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 second. The transformations between coexisting phases are accompanied by a continuous change in the nanoparticles film’s reflectivity. The transformations are believed to belong to surface-driven excitation-induced phase transitions.
Experimental results suggests that both thermal and non-thermal mechanisms contribute to the effect observed in both laser and electron beam excitation. Calculations of gallium nanoparticles films optical properties support the strength of the model.
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Published date: 2004
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Local EPrints ID: 465477
URI: http://eprints.soton.ac.uk/id/eprint/465477
PURE UUID: ae52c677-282b-4264-ba4e-7f009b7a4277
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Date deposited: 05 Jul 2022 01:18
Last modified: 05 Jul 2022 01:18
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Author:
Sebastien Claude Pochon
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