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Ordered Au nanocrystals on a substrate formed by light-induced rapid annealing
KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.ORCID iD: 0000-0002-0111-9009
KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.ORCID iD: 0000-0002-3368-9786
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2014 (English)In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 6, no 3, 1756-1762 p.Article in journal (Refereed) Published
Abstract [en]

Light-induced rapid annealing (LIRA) is a widely used method to modify the morphology and crystallinity of noble metal nanoparticles, and the nanoparticles generally evolve into nanospheres. It is rather challenging to form faceted Au nanocrystals on a substrate using LIRA. Here the formation of spatially ordered Au nanocrystals using a continuous wave infrared laser is reported, assisted by a metamaterial perfect absorber. Faceted Au nanocrystals in truncated-octahedral or multi-twinned geometries can be obtained. The evolution of morphology and crystallinity of the Au nanoparticles during laser annealing is also revealed, where the crystal grain growth and the surface melting are shown to play key roles in nanocrystal formation. The evolution of morphology also gives the freedom of tuning the absorption spectrum of the metamaterial absorber. These findings provide a novel way for tailoring the morphology and crystallinity of metallic nanoparticles and may pave the way to fabricate refined nano-devices in many potential applications for optics, electronics, catalysis, surface-chemistry and biology.

Place, publisher, year, edition, pages
2014. Vol. 6, no 3, 1756-1762 p.
Keyword [en]
Gold Nanoparticles, Laser-Pulses, Arrays, Femtosecond, Fabrication, Absorber, Surfaces, Growth
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:kth:diva-141722DOI: 10.1039/c3nr05745cISI: 000330041400069Scopus ID: 2-s2.0-84892640438OAI: oai:DiVA.org:kth-141722DiVA: diva2:698358
Funder
Swedish Foundation for Strategic Research Swedish Research Council
Note

QC 20140221

Available from: 2014-02-21 Created: 2014-02-21 Last updated: 2017-12-05Bibliographically approved
In thesis
1. Photothermal Effect in Plasmonic Nanostructures and its Applications
Open this publication in new window or tab >>Photothermal Effect in Plasmonic Nanostructures and its Applications
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

  Plasmonic resonances are characterized by enhanced optical near field and subwavelength power confinement. Light is not only scattered but also simultaneously absorbed in the metal nanostructures. With proper structural design, plasmonic-enhanced light absorption can generate nanoscopically confined heat power in metallic nanostructures, which can even be temporally modulated by varying the pump light. These intrinsic characters of plasmonic nanostructures are investigated in depth in this thesis for a range of materials and nanophotonic applications.

  The theoretical basis for the photothermal phenomenon, including light absorption, heat generation, and heat conduction, is coherently summarized and implemented numerically based on finite-element method. Our analysis favours disk-pair and particle/dielectric-spacer/metal-film nanostructures for their high optical absorbance, originated from their antiparallel dipole resonances.

  Experiments were done towards two specific application directions. First, the manipulation of the morphology and crystallinity of Au nanoparticles (NPs) in plasmonic absorbers by photothermal effect is demonstrated. In particular, with a nanosecond-pulsed light, brick-shaped Au NPs are reshaped to spherical NPs with a smooth surface; while with a 10-second continuous wave laser, similar brick-shaped NPs can be annealed to faceted nanocrystals. A comparison of the two cases reveals that pumping intensity and exposure time both play key roles in determining the morphology and crystallinity of the annealed NPs.

  Second, the attempt is made to utilize the high absorbance and localized heat generation of the metal-insulator-metal (MIM) absorber in Si thermo-optic switches for achieving all-optical switching/routing with a small switching power and a fast transient response. For this purpose, a numerical study of a Mach-Zehnder interferometer integrated with MIM nanostrips is performed. Experimentally, a Si disk resonator and a ring-resonator-based add-drop filter, both integrated with MIM film absorbers, are fabricated and characterized. They show that good thermal conductance between the absorber and the Si light-guiding region is vital for a better switching performance.

  Theoretical and experimental methodologies presented in the thesis show the physics principle and functionality of the photothermal effect in Au nanostructures, as well as its application in improving the morphology and crystallinity of Au NPs and miniaturized all-optical Si photonic switching devices.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2014. xvi, 94 p.
Series
TRITA-ICT/MAP AVH, ISSN 1653-7610 ; 2014:04
Keyword
Plasmonic, Photothermal Effect, Silicon Photonics, Gold Nanoparticles
National Category
Atom and Molecular Physics and Optics
Research subject
Physics
Identifiers
urn:nbn:se:kth:diva-143754 (URN)978-91-7595-059-4 (ISBN)
Public defence
2014-04-22, Sal/hall D, KTH-ICT, Isafjordsgatan 39, Kista, 14:00 (English)
Opponent
Supervisors
Funder
Swedish Research Council, 63183
Note

QC 20140331

Available from: 2014-03-31 Created: 2014-03-27 Last updated: 2014-03-31Bibliographically approved

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Dai, JinYan, Min

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