Stiffened Ultrathin Pt Films Confirmed by Acoustic-Phonon Resonances

Ogi, Hirotsugu; Fujii, Makoto; Nakamura, Nobutomo; Yasui, Takeshi; Hirao, Masahiko

doi:10.1103/physrevlett.98.195503

Cited by 65 publications

(90 citation statements)

References 24 publications

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“…Coherent acoustic phonons, by contrast, are ultrasonic strain pulses that can have a broad spectrum from GHz up to a few THz frequencies and wide range of wavevectors q. Propagation of the coherent acoustic phonons has been studied in various materials by means of time-resolved optical [2][3][4][5] and x-ray diffraction [6,7] measurements. Such studies are motivated by optical determination of the mechanical properties of solids [8,9], optical control of acoustic waves in solids [10], acoustic tomography of buried interfaces and objects hidden under surfaces [11,12], and ultrafast optical control of the piezoelectric effect [13].…”

Section: Introductionmentioning

confidence: 99%

Intrinsic coherent acoustic phonons in the indirect band gap semiconductors Si and GaP

et al. 2017

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We report on the intrinsic optical generation and detection of coherent acoustic phonons at (001)-oriented bulk Si and GaP without metallic phonon transducer structures. Photoexcitation by a 3.1-eV laser pulse generates a normal strain pulse within the ∼100-nm penetration depth in both semiconductors. The subsequent propagation of the strain pulse into the bulk is detected with a delayed optical probe as a periodic modulation of the optical reflectivity. Our theoretical model explains quantitatively the generation of the acoustic pulse via the deformation potential electronphonon coupling and detection in terms of the spatially and temporally dependent photoelastic effect for both semiconductors. Comparison with our theoretical model reveals that the strain pulses have finite build-up times of 1.2 and 0.4 ps for GaP and Si, which is comparable with the intervalley scattering time constant required for the photoexcited electrons to reach the conduction band minimum. The deformation potential coupling related to the acoustic pulse generation for GaP is estimated to be twice as strong as that for Si from our experiments, in agreement with a previous theoretical prediction.

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Section: Introductionmentioning

confidence: 99%

Intrinsic coherent acoustic phonons in the indirect band gap semiconductors Si and GaP

et al. 2017

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“…Hence, the characteristics of the sample can be obtained by measurement of resonant frequencies, supported by a modal analysis. The method has been applied for thinlayered systems to determine the mechanical characteristics, e.g., accurate elastic constants of thin-layers on substrates [11,12] and the stress state of thin-films [13,14].…”

Section: Introductionmentioning

confidence: 99%

Mechanical Characteristics of Electrolytes Assessed with Resonant Ultrasound Spectroscopy

et al. 2013

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Elastic properties and residual stresses are critical for the assessment of the reliability of ceramics components. The thin electrolyte layer of anode supported SOFCs is under a state of high compressive residual stress. In the present study, the elastic properties of this layer as well as the residual stress distribution induced in the anode‐supported planar SOFC cell were examined by using the resonant ultrasound spectroscopy (RUS). A modal analysis by finite element simulation demonstrated that the RUS has a great potential to determine these mechanical characteristics. The Young's modulus can be determined from the natural frequencies of the layered sample whilst the residual stress can be determined using the sample with a semi‐hole. Estimates of the Poisson's ratio are possible. In the experiment, various individual resonant oscillations were successfully identified using the present RUS system. Hence, by comparison of experimental results and simulations, the elastic properties as well as the residual stress were obtained. Although the proposed method is still experimentally challenging, it could be developed to become a powerful tool to simultaneously determine residual stresses and elastic constants of thin‐layered systems.

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“…Then, the C 33 is determined from the round-trip traveling time. (12), (13) When the film thickness is smaller than the pulse width, the acousticpulse wave overlaps, and standing phonon vibrations occur. (14), (15) Because C 33 governs their resonance frequencies, we can determine the C 33 from the resonance frequency.…”

Section: Journal Of Solid Mechanics and Materials Engineeringmentioning

confidence: 99%

Laser-Induced Coherent Acoustic Phonons for Measuring Elastic Constants of Ultra-Thin Films

Nakamura

Uranishi

Shagawa

et al. 2008

JMMP

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We determine the out-of-plane elastic constants C 33 of ultra-thin films using gigahertz coherent acoustic phonons. Acoustic phonons are generated and detected using femtosecond-laser pulses, and by measuring the resonance frequency of non-propagating acoustic phonons in thin films, C 33 is determined. In determining the C 33 , film thickness and mass density are required, and we determine them by the x-ray reflectivity measurements. We apply this method to the Fe thin films of 11-52 nm thickness. When the film thickness is 11 nm, C 33 was larger than C 33 of the bulk Fe. As the film thickness increases, C 33 decreases, and when the film thickness is larger than 35 nm, C 33 was smaller than the bulk value. However, by heating the substrate, C 33 shows recovery towards the bulk value. There results are explained by the incohesive bonding at grain boundaries and residual stress.

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Stiffened Ultrathin Pt Films Confirmed by Acoustic-Phonon Resonances

Cited by 65 publications

References 24 publications

Intrinsic coherent acoustic phonons in the indirect band gap semiconductors Si and GaP

Intrinsic coherent acoustic phonons in the indirect band gap semiconductors Si and GaP

Mechanical Characteristics of Electrolytes Assessed with Resonant Ultrasound Spectroscopy

Laser-Induced Coherent Acoustic Phonons for Measuring Elastic Constants of Ultra-Thin Films

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