<i>In situ</i> spectroscopic ellipsometry to monitor surface plasmon resonant group-III metals deposited by molecular beam epitaxy

Wu, Pae C.; Losurdo, Maria; Kim, Tong-Ho; Choi, Sunghee; Bruno, Giovanni; Brown, April S.

doi:10.1116/1.2734163

Cited by 31 publications

(43 citation statements)

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“…31,63 Real-time monitoring of this process was performed by in situ spectroscopic ellipsometry (SE) from λ 0 = 200À820 nm at a 20°g razing angle of incidence, permitting the termination of growth when the desired optical properties were attained ( Figure 1E). 6,30 Samples were stored in ambient atmosphere for 21 months prior to the CL measurements, demonstrating the robustness of the native oxide shell.…”

Section: Methodsmentioning

confidence: 99%

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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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Section: Methodsmentioning

confidence: 99%

“…6,30 The experimentally measured ellipsometric parameters Δ and ψ were converted to a pseudodielectric function following the method described previously. 6,24 The initial pseudodielectric function closely matches the response of crystalline silicon ( Figure 1E, green lines).…”

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

et al. 2015

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“…20,[24][25][26]29,30,46 The samples were subsequently measured more extensively ex situ with a J. A. Woollam Co., Inc. VASE system to collect angle-and energy-resolved VAMM and scattering spectra.…”

Section: Acs Photonicsmentioning

confidence: 99%

“…25−30 Specifically, this technique has been used to demonstrate the correlation between mean NP size and the inplane and out-of-plane localized surface plasmon resonance (LSPR) modes of substrate-supported Ga NPs. 20,29,30 This approach allows the operator to tune the plasmon resonance to a desired wavelength on any substrate, providing real-time feedback for fabricating structures optimized for plasmonic applications such as UV-SERS, 31,32 but a deeper analysis is needed to reveal how the measured plasmon resonance frequencies and widths of self-assembled NP ensembles relate to the mean NP size and spatial distribution, respectively. This problem is exacerbated by the fact that LSPRs depend also on the substrate and inter-NP interactions.…”

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Ultraviolet–Visible Plasmonic Properties of Gallium Nanoparticles Investigated by Variable-Angle Spectroscopic and Mueller Matrix Ellipsometry

et al. 2014

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Self-assembled, irregular ensembles of hemispherical Ga nanoparticles (NPs) were deposited on sapphire by molecular beam epitaxy. These samples, whose constituent unimodal or bimodal distribution of NP sizes was controlled by deposition time, exhibited localized surface plasmon resonances tunable from the ultraviolet to the visible (UV/ vis) spectral range. The optical response of each sample was characterized using a variable-angle spectroscopic ellipsometer, and the dielectric response of the ensemble of NPs on each sample was parametrized using Lorentz oscillators. From this, a relationship was found between NP size and the deduced Lorentzian parameters (resonant frequency, damping, oscillator strength) for most unimodal and bimodal samples at most frequencies and angles of incidence. However, for samples with a bimodal size distribution, Mueller matrix ellipsometry revealed nonspecular scattering at particular frequencies and angles, suggesting a resonant interparticle coupling effect consistent with recently observed strong local field enhancements in the ultraviolet. KEYWORDS: plasmonics, ultraviolet, gallium, nanoparticles, variable-angle spectroscopic ellipsometry, variable-angle Mueller matrix ellipsometry R esearch into the optical response of confined electronic plasma oscillations in metallic nanostructures has become the foundation of modern plasmonics. Metallic nanostructures are routinely fabricated with desired spatial geometries for specific applications including single-molecule detection, enhanced fluorescence, toxic remediation, and catalysis. 1−6 Because the optical response depends sensitively on nanostructure composition, size, and shape, increasingly sophisticated characterization tools are required: aggregate behavior may be characterized by absorption spectroscopy or dark-field microscopy, while single-particle behavior may be characterized by confocal microscopy, near-field scanning optical microscopy, and cathodoluminescence. 7−12 These tools provide incredibly detailed understanding of the absorption and scattering properties of plasmonic metal nanoparticles, especially when complemented by sophisticated electromagnetic modeling techniques such as finite difference time domain, finite element codes, and the discrete dipole approximation. 13−19 Of growing interest is the need to monitor the plasmonic properties of substrate-supported nanoparticle (NP) ensembles during fabrication. Because it is impractical to use single-particle imaging tools for this application, advances in the more traditional tools are needed to understand single-particle behaviors from aggregate measurements. Spectroscopic ellipsometry (SE) has been used to monitor how NP ensembles alter the polarization state of an incident light beam as a function of wavelength and incidence angle. 20−24 Recently, a fixed incidence angle spectroscopic ellipsometer mounted on a molecular beam epitaxy (MBE) chamber has been used to monitor in real time the deposition of nanometer-scale metallic films and NPs through...

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Gallium Plasmonic Nanoantennas Unveiling Multiple Kinetics of Hydrogen Sensing, Storage, and Spillover

et al. 2021

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hydrogen sensing and storage new materials solutions are needed to reduce thermodynamic (process-temperatures limitations) and kinetic (process rate limitations) barriers and meet the challenges of sensing of a response time of less than 1 s, an operating temperature of −30 to 80 degrees Celsius, and a measurement of 0.1% to 10%, [1] as well as of hydrogen storage with low hydrogen refilling time and output power.The integration of plasmonics [2] with the recently introduced concept of novel catalytically-active liquid metal hydrides and hydrogen trapping mechanisms represents a breakthrough toward creating a new generation of plasmonic-enhanced photocatalytic nanosystems for enhancing both hydrogen sensing [3] and storage. [4] Surface-plasmon-resonance (SPR) induces electromagnetic field enhancement on common hydrogen-absorbing metals such as magnesium (Mg), palladium (Pd), titanium (Ti), and nickel (Ni) which may be exploitable in the microwave region for hydrogen storage. [5,6] Previous studies have reported SPR hydrogen sensing platforms based on Pd, [7,8] gold (Au), [9][10][11] aluminum (Al), [12] and Mg [13] nanoparticles (NPs). Considering the essential requirements for hydrogen storage, such as high storage capacity and fast hydrogen adsorption kinetics, requirements of hydrogen Hydrogen is the key element to accomplish a carbon-free based economy. Here, the first evidence of plasmonic gallium (Ga) nanoantennas is provided as nanoreactors supported on sapphire (α-Al 2 O 3 ) acting as direct plasmonenhanced photocatalyst for hydrogen sensing, storage, and spillover. The role of plasmon-catalyzed electron transfer between hydrogen and plasmonic Ga nanoparticle in the activation of those processes is highlighted, as opposed to conventional refractive index-change-based sensing. This study reveals that, while temperature selectively operates those various processes, longitudinal (LO-LSPR) and transverse (TO-LSPR) localized surface plasmon resonances of supported Ga nanoparticles open selectivity of localized reaction pathways at specific sites corresponding to the electromagnetic hot-spots. Specifically, the TO-LSPR couples light into the surface dissociative adsorption of hydrogen and formation of hydrides, whereas the LO-LSPR activates heterogeneous reactions at the interface with the support, that is, hydrogen spillover into α-Al 2 O 3 and reverse-oxygen spillover from α-Al 2 O 3. This Ga-based plasmon-catalytic platform expands the application of supported plasmoncatalysis to hydrogen technologies, including reversible fast hydrogen sensing in a timescale of a few seconds with a limit of detection as low as 5 ppm and in a broad temperature range from room-temperature up to 600 °C while remaining stable and reusable over an extended period of time.

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In situ spectroscopic ellipsometry to monitor surface plasmon resonant group-III metals deposited by molecular beam epitaxy

Abstract: Articles you may be interested inMeasuring the localized surface plasmon resonance effect on large arrays (5mm × 5mm) of gold and aluminum nanoparticles on borosilicate glass substrates, fabricated by electron beam lithography

Cited by 31 publications

References 31 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

Ultraviolet–Visible Plasmonic Properties of Gallium Nanoparticles Investigated by Variable-Angle Spectroscopic and Mueller Matrix Ellipsometry

Gallium Plasmonic Nanoantennas Unveiling Multiple Kinetics of Hydrogen Sensing, Storage, and Spillover

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