Time-resolved thermoreflectivity of thin gold films and its dependence on film thickness

Hohlfeld, J.; Müller, J.G.; Wellershoff, S.-S.; Matthias, E.

doi:10.1007/s003400050189

Cited by 138 publications

(76 citation statements)

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“…The pump excites a plasmon that rapidly decays to non-thermalized electrons 25 . The electrons thermalize through scattering processes on a sub-picosecond timescale raising the electronic temperature and changing the interband transition rates 26 : producing a sharp peak in the transient transmission measurement 16 . The electrons then rapidly heat the lattice through electron-phonon scattering, which generates coherent acoustic phonons, the sinusoidal oscillations with a period of B100 ps.…”

Section: Resultsmentioning

confidence: 99%

“…The electrons then superdiffuse throughout the nanostructure at the Fermi velocity (B10 6 m s À 1 ), distributing their kinetic energy over the nanostructure within B100 fs (ref. 16). The electrons transfer energy to the lattice, resulting in a rapid thermal expansion of the structure that sets off oscillations between the initial and expanded lattice spacing, known as coherent acoustic phonons.…”

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confidence: 99%

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Ultrafast acousto-plasmonic control and sensing in complex nanostructures

et al. 2014

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Coherent acoustic phonons modulate optical, electronic and mechanical properties at ultrahigh frequencies and can be exploited for applications such as ultratrace chemical detection, ultrafast lasers and transducers. Owing to their large absorption cross-sections and high sensitivities, nanoplasmonic resonators are used to generate coherent phonons up to terahertz frequencies. Generating, detecting and controlling such ultrahigh frequency phonons has been a topic of intense research. Here we report that by designing plasmonic nanostructures exhibiting multimodal phonon interference, we can detect the spatial properties of complex phonon modes below the optical wavelength through the interplay between plasmons and phonons. This allows detection of complex nanomechanical dynamics by polarization-resolved transient absorption spectroscopy. Moreover, we demonstrate that the multiple vibrational states in nanostructures can be tailored by manipulating the geometry and dynamically selected by acousto-plasmonic coherent control. This allows enhancement, detection and coherent generation of tunable strains using surface plasmons.

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Section: Resultsmentioning

confidence: 99%

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confidence: 99%

Ultrafast acousto-plasmonic control and sensing in complex nanostructures

et al. 2014

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“…In addition to being an optical non-invasive technique, thermoreflectance has the potential for providing micron-scale spatial resolution and sub-nanosecond temporal resolution [6,[24][25][26][27].…”

Section: Principles and Technical Backgroundmentioning

confidence: 99%

“…Typically, κ is on the order of 10 -4 -10 -6 K -1 and depends on the wavelength that is used to probe the surface [20][21][22][23]. In addition to being a purely optical, non-invasive technique, thermoreflectance has the potential for providing micron-scale spatial resolution and subnanosecond temporal resolution [6,[24][25][26][27]. While spatial resolution is limited by the diffraction limit of the optics involved in the detection scheme, the theoretical limit of the temporal resolution is determined by the order of the processes involved in the reflectance, which can be on the order of picoseconds in metals [20].…”

Section: Introductionmentioning

confidence: 99%

Noncontact surface thermometry for microsystems: LDRD final report.

Abel

Beecham

Graham

et al. 2006

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We describe a Laboratory Directed Research and Development (LDRD) effort to develop and apply laser-based thermometry diagnostics for obtaining spatially resolved temperature maps on working microelectromechanical systems (MEMS). The goal of the effort was to cultivate diagnostic approaches that could adequately resolve the extremely fine MEMS device features, required no modifications to MEMS device design, and which did not perturb the delicate operation of these extremely small devices. Two optical diagnostics were used in this study: microscale Raman spectroscopy and microscale thermoreflectance. Both methods use a low-energy, nonperturbing probe laser beam, whose arbitrary wavelength can be selected for a diffraction-limited focus that meets the need for micron-scale spatial resolution. Raman is exploited most frequently, as this technique provides a simple and unambiguous measure of the absolute device temperature for most any MEMS semiconductor or insulator material under steady state operation. Temperatures are obtained from the spectral position and width of readily isolated peaks in the measured Raman spectra with a maximum uncertainty near ±10 K and a spatial resolution of about 1 micron. Application of the Raman technique is demonstrated for V-shaped and flexure-style polycrystalline silicon electrothermal actuators, and for a GaN high-electron-mobility transistor. The potential of the Raman technique for simultaneous measurement of temperature and inplane stress in silicon MEMS is also demonstrated and future Raman-variant diagnostics for ultra spatiotemporal resolution probing are discussed. Microscale thermoreflectance has been developed as a complement for the primary Raman diagnostic. Thermoreflectance exploits the small-but-measurable temperature dependence of surface optical reflectivity for diagnostic purposes. The temperaturedependent reflectance behavior of bulk silicon, SUMMiT-V polycrystalline silicon films and metal surfaces is presented. The results for bulk silicon are applied to silicon-on-insulator (SOI) fabricated actuators, where measured temperatures with a maximum uncertainty near ±9 K, and 0.75-micron inplane spatial resolution, are achieved for the reflectance-based measurements. Reflectance-based temperatures are found to be in good agreement with Raman-measured temperatures from the same device. Constructive peer-reviews of this report were provided by Ed Piekos and Carlton Brooks. 4 ACKNOWLEDGEMENTS5

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“…During a very short timescale, electron-electron scattering gives rise to hot electrons that are not in thermodynamic equilibrium with the Ag lattice before typically few hundreds of fs. These non-equilibrium electrons penetrate into the material with ballistic velocities of the order of 10 6 m/s, 30 and their energy range is estimated between 1 eV and 4 eV for Ag NPs. 31 Those electrons whose kinetic energy overcomes the Schottky barrier that forms at the metal nanoparticles / TiO 2 interface and that can be as low as 1 eV in such systems, can be injected into the TiO 2 , as shown in Fig.…”

Section: Short Timescale: Charge Transfer From Ag Nps To the Tio 2 Comentioning

confidence: 99%

Three-Dimensional Self-Organization in Nanocomposite Layered Systems by Ultrafast Laser Pulses

et al. 2017

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Controlling plasmonic systems with nanometre resolution in transparent films and their colors over large non-planar areas is a key issue for spreading their use in various industrial fields. Using light to direct self-organization mechanisms provides high-speed and flexible processes to meet this challenge. Here, we describe a route for the laser-induced self-organization of metallic nanostructures in 3D. Going beyond the production of planar nanopatterns, we demonstrate that ultrafast laser-induced excitation combined with non-linear feedback mechanisms in a nanocomposite thin film can lead to 3D self-organized nanostructured films. The process, which can be extended to complex layered composite systems, produces highly uniform large-area nanopatterns. We show that 3D self-organization originates from the simultaneous excitation of independent optical modes at different depths in the film and is activated by the plasmon-induced charge separation and thermally-induced NP growth mechanisms. This laser color marking technique enables multiplexed optical image encoding and the generated nanostructured Ag NPs:TiO 2 films offer great promise for applications in solar energy harvesting, photocatalysis or photochromic devices. KeywordsUltrafast photonics; Laser-induced self-organization; Nanostructured thin film; plasmonic nanomaterials; plasmonic colors Controlling metallic nanostructures over large non-planar areas with high flexibility and speed is of strategic importance for developing industrial applications of plasmonic systems.

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Time-resolved thermoreflectivity of thin gold films and its dependence on film thickness

Cited by 138 publications

References 0 publications

Ultrafast acousto-plasmonic control and sensing in complex nanostructures

Ultrafast acousto-plasmonic control and sensing in complex nanostructures

Noncontact surface thermometry for microsystems: LDRD final report.

Three-Dimensional Self-Organization in Nanocomposite Layered Systems by Ultrafast Laser Pulses

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