Optical control of gallium nanoparticle growth

MacDonald, Kevin F.; Fedotov, V.A.; Pochon, S.; Ross, K J; Stevens, G.C.; Zheludev, Nikolay I.; Brocklesby, W.S.; Emel’yanov, V. I.

doi:10.1063/1.1456260

Cited by 75 publications

(52 citation statements)

References 30 publications

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“…These methods include self-assembly during molecular beam epitaxy (MBE), 6,7 optically regulated self-assembly, 8 thermal evaporation, 9 and colloidal synthesis. 10 When exposed to atmosphere following synthesis, Ga NPs form a thin, self-terminating native oxide shell that protects the pure metallic core.…”

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confidence: 99%

Gallium Plasmonics: Deep Subwavelength Spectroscopic Imaging of Single and Interacting Gallium Nanoparticles

et al. 2015

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Gallium has recently been demonstrated as a phasechange plasmonic material offering UV tunability, facile synthesis, and a remarkable stability due to its thin, self-terminating native oxide. However, the dense irregular nanoparticle (NP) ensembles fabricated by molecular-beam epitaxy make optical measurements of individual particles challenging. Here we employ hyperspectral cathodoluminescence (CL) microscopy to characterize the response of single Ga NPs of various sizes within an irregular ensemble by spatially and spectrally resolving both in-plane and out-of-plane plasmonic modes. These modes, which include hybridized dipolar and higher-order terms due to phase retardation and substrate interactions, are correlated with finite difference time domain (FDTD) electrodynamics calculations that consider the Ga NP contact angle, substrate, and native Ga/Si surface oxidation. This study experimentally confirms previous theoretical predictions of plasmonic size-tunability in single Ga NPs and demonstrates that the plasmonic modes of interacting Ga nanoparticles can hybridize to produce strong hot spots in the ultraviolet. The controlled, robust UV plasmonic resonances of gallium nanoparticles are applicable to energy-and phase-specific applications such as optical memory, environmental remediation, and simultaneous fluorescence and surface-enhanced Raman spectroscopies.

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confidence: 99%

Gallium Plasmonics: Deep Subwavelength Spectroscopic Imaging of Single and Interacting Gallium Nanoparticles

et al. 2015

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“…The atomic transport in adsorbing porous materials is governed by the adsoprtion/desorption events at the pore's surface, where atomic nanoaggregates are assembled as a consequence of atomic surface diffusion and nucleation [2,6,7,8]. Many experiments involving different adsorbates and substrates demonstrated that light can influence the formation of nanostructures [9,10,11,12,13,14].In particular, in porous materials loaded with alkali-metal atoms, it has been proved that atomic photo-desorption [15] plays a key role in cluster growth [6,16]. Upon visible illumination, the atomic desorption probability from atomic layers covering the pore's surface increases; consequently also the atomic diffusion coefficient, which is proportional to the desorbing rate, rises.…”

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Laser-driven self-assembly of shape-controlled potassium nanoparticles in porous glass

et al. 2014

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Abstract. We observe growth of shape-controlled potassium nanoparticles inside a random network of glass nanopores, exposed to low-power laser radiation. Visible laser light plays a dual role: it increases the desorption probability of potassium atoms from the inner glass walls and induces the self-assembly of metastable metallic nanoparticles along the nanopores. By probing the sample transparency and the atomic light-induced desorption flux into the vapour phase, the dynamics of both cluster formation/evaporation and atomic photo-desorption processes are characterized. Results indicate that laser light not only increases the number of nanoparticles embedded in the glass matrix but also influences their structural properties. By properly choosing the laser frequency and the illumination time, we demonstrate that it is possible to tailor the nanoparticles' shape distribution. Furthermore, a deep connection between the macroscopic behaviour of atomic desorption and light-assisted cluster formation is observed. Our results suggest new perspectives for the study of atom/surface interaction as well as an effective tool for the light-controlled reversible growth of nanostructures.PACS numbers: 78.67. Bf, 36.40.Mr, 78.67.Rb Keywords: laser-control of atomic transport, nanoparticles self-assembly, nanoporous materials. Laser driven self-assembly of shape-controlled potassium nanoparticles in porous glass2Atomic adsorption and desorption have a major influence on surface processes and related transport phenomena [1,2,3]. Their control provides a tool for driving the evolution of nanoscale systems, where the atomic mobility is strongly affected by the interaction with the substrate [4,2,5]. The atomic transport in adsorbing porous materials is governed by the adsoprtion/desorption events at the pore's surface, where atomic nanoaggregates are assembled as a consequence of atomic surface diffusion and nucleation [2,6,7,8]. Many experiments involving different adsorbates and substrates demonstrated that light can influence the formation of nanostructures [9,10,11,12,13,14].In particular, in porous materials loaded with alkali-metal atoms, it has been proved that atomic photo-desorption [15] plays a key role in cluster growth [6,16]. Upon visible illumination, the atomic desorption probability from atomic layers covering the pore's surface increases; consequently also the atomic diffusion coefficient, which is proportional to the desorbing rate, rises. The atomic motion can be thus modelled as a random sequence of free flights between the pore walls, interrupted by adsorption events at the nanopore surface [2]. As an atom sticks to the surface, it can be either desorbed again -with a light-enhanced probability -or can be trapped at surface defects where metastable metallic nanoparticles (NPs), characterized by defined surface plasmon bands, are formed [6,7].In this work, we use low-power visible laser irradiation to induce atomic desorption and, thus, the formation of K NPs inside a nanoporous glass matrix. Our results in...

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“…The particles, typically 50 nm in diameter with a relatively narrow size distribution (±14 nm), were prepared on the tips of silica optical fibers, using the recently developed light-assisted self-assembly technique [6,7]. This process produced a nanoparticle film on the fiber's core (9 µm in diameter) comprising ∼2.…”

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

MacDonald¹,

Fedotov²,

Pochon³

et al. 2004

Europhys. Lett.

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We have observed reversible structural transformations, induced by optical excitation at 1.55 µm, between the β, γ 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.We report that the coexistence of different crystalline and disordered phases in nanoparticles can be controlled by optical excitation in a controllable, continuous and reversible fashion. This has been observed in nanoparticles of polymorphic elemental gallium. Shifts in the balance between phases are accompanied substantial changes in the optical properties of the nanoparticle film. The light-induced transformations display phenomenological features typical of 1st-order Ehrenfest phase transitions (such as a reflectivity hysteresis) but simultaneously display characteristics of 2nd-order transitions (such as critical dependencies on temperature of the 'susceptibility' and relaxation time of the stimulated response). Our study is motivated by a desire to understand the exciting physics of phase equilibria in nanoparticles [1,2,3] and in particular in metallic nanoparticles, which have the potential to play a key role in future highly integrated photonic devices as the active elements of waveguiding [4] and switching [5] structures.We studied light-induced structural transformations in gallium nanoparticles by monitoring the optical reflectivity of nanoparticle films. The particles, typically 50 nm in diameter with a relatively narrow size distribution (±14 nm), were prepared on the tips of silica optical fibers, using the recently developed light-assisted self-assembly technique [6,7]. This process produced a nanoparticle film on the fiber's core (9 µm in diameter) comprising ∼2.10 4 nanoparticles. Phase transitions in the nanoparticles ware stimulated by a 1.4 mW , 1.55 µm diode laser launched into the fiber. Its output was modulated with 50% duty cycle at 6.2 kHz providing an average excitation power of about 22 nW per nanoparticle. Another 0.4 mW cw diode laser operating at 1.31 µm and phasesensitive detection apparatus were used to monitor the reflectivity of the film. The detection system had an overall bandwidth of 300 kHz.The nanoparticle film's reflectivity shows a very wide (>100 K) hysteresis, with two distinct steps, at T ′ 0 ∼ 233 K and T 0 ∼ 253 K, in the rising temperature part of the cycle (Fig. 1a). The presence of these steps indicates that there are two structural phase transitions and therefore that either the nanoparticles undergo a transition from one solid phase to another and then from that phase to the liquid, or that two solid phases coexist at low tem...

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Optical control of gallium nanoparticle growth

Cited by 75 publications

References 30 publications

Gallium Plasmonics: Deep Subwavelength Spectroscopic Imaging of Single and Interacting Gallium Nanoparticles

Gallium Plasmonics: Deep Subwavelength Spectroscopic Imaging of Single and Interacting Gallium Nanoparticles

Laser-driven self-assembly of shape-controlled potassium nanoparticles in porous glass

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

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