HAL (Le Centre pour la Communication Scientifique Directe), Apr 12, 2010
Dans ce travail experimental, nous avons etudie la refraction dondes elastiques de surface par u... more Dans ce travail experimental, nous avons etudie la refraction dondes elastiques de surface par un cristal phononique 2D a matrice solide. Nous decrirons les deux techniques experimentales qui ont ete utilisees. Des ondes elastiques de surface dans la gamme du MHz sont engendrees et detectees par une technique de laser-ultrasons (acoustique nanoseconde), alors que lacoustique picoseconde est utilisee pour les ondes au GHz. Les echantillons consistent en un arrangement periodique de trous dans un substrat solide (ondes de Rayleigh) ou dans une plaque depaisseur finie(ondes de Lamb). Nous avons mesure des deplacements de surface dans la zone de refraction negative pour differents parametres geometriques du reseau phononique. Nous attribuons ces modes de vibration au repliement des courbes de dispersion induit par la periodicite du milieu. Ces resultats experimentaux seront ensuite compares aux predictions theoriques.
Buckling structures that cannot be simply understood in the frame of continuum elastic theory hav... more Buckling structures that cannot be simply understood in the frame of continuum elastic theory have been observed by atomic force microscopy on gold films, 630 nm thick, deposited by sputtering method on silicon substrates. X-ray diffraction analyses and finite element simulations have been carried out to characterize the stress levels in and around these buckling structures. The high stress concentration
We report on thermal investigations performed in a time resolved experimental scheme. The time do... more We report on thermal investigations performed in a time resolved experimental scheme. The time domain thermoreflectance (TDTR) is applied in an unusual geometry where the pump and probe beams are not superimposed but focused and shifted. In this way, the determination of the in-plane thermal diffusivity is achieved from temperature snapshots at different time delays. In the first part, taking into account the specific generation process and the detection inherent to the time domain thermoreflectance approach, an analytical solution for the temperature field is obtained for bulk samples, and compared to experimental data. A comparison with the frequency domain thermoreflectance microscopy is also outlined. In Part II section, the lateral heat diffusion in a layered structure is investigated. The comparison of the heat diffusion spreading in case of a highly conductive layer deposited on an insulator substrate and the reverse situation are carefully studied. Finally, we show how the time dependence is efficient to probe and identify material thermal properties or thermal interfacial resistance.
We present a new method to measure without any calibration the thermal effusivity, conductivity, ... more We present a new method to measure without any calibration the thermal effusivity, conductivity, and diffusivity of an insulating layer deposited on a substrate, using lateral heat diffusion. The method is applied to Lithium phosphorous oxynitride, a thin film solid-state electrolyte used in micro-batteries.
To characterize the mechanical properties of elastic thin films to improve the lifetime of LMJ co... more To characterize the mechanical properties of elastic thin films to improve the lifetime of LMJ components, two experimental setups have been used: the acoustic picosecond techniques and the Surface Acoustic Wave InterDigital Transducers.
Journal of the Acoustical Society of America, May 1, 2017
The mechanical properties of thin films involved in the manufacturing of ophthalmic glasses have ... more The mechanical properties of thin films involved in the manufacturing of ophthalmic glasses have been investigated by two complementary laser based techniques. On the one hand, picosecond ultrasonics (PU) measurements allows to determine the acoustical longitudinal velocity in the sample, hence the elastic constant c11. On the other hand, Brillouin light scattering (BLS) measurements leads to the value of the transverse velocity, hence c44. In the case of isotropic materials, these two coefficients give a direct access to the value of the Young’s modulus and Poisson’s ratio of the film. The influence of the film characteristics on its mechanical properties will be discussed, mainly regarding its thickness and the manufacturing process. Another issue concerning the effect of the film environment will be addressed. Especially, we will discuss the influence of the substrate on the mechanical properties of a single film, and the link between the mechanical properties of a single film and the ones of a films stacking.
Journal of the Acoustical Society of America, May 1, 2008
In standard ultrafast acoustic experiments very short coherent acoustic pulses are generated by t... more In standard ultrafast acoustic experiments very short coherent acoustic pulses are generated by the absorption of a femtosecond laser pulse in a thin metallic transducer deposited on the sample. Subsequently the acoustic pulses and the heat generated in the transducer cross the sample and are partially transmitted in the underlaying substrate. At low temperature, heating of the metallic transducer gives rise to the emission of incoherent phonons wave packets which propagate ballistically over large distances in the substrate. We report on a series of experiments which demonstrate the acoustic rectification [1-3] of these wave packets as they propagate through large GaAs or Si substrates. [1] B. Perrin, J. de Phys. C8 (1979) 216. [2] S. M. Avanesyan, V. E. Gusev, Solid State. Commun. 54 (1985) 1065. [3] B. Perrin, E. Péronne, L. Belliard, Ultrasonics, 44 (2006) 1277.
HAL (Le Centre pour la Communication Scientifique Directe), Apr 12, 2010
Dans ce travail experimental, nous avons etudie la refraction dondes elastiques de surface par u... more Dans ce travail experimental, nous avons etudie la refraction dondes elastiques de surface par un cristal phononique 2D a matrice solide. Nous decrirons les deux techniques experimentales qui ont ete utilisees. Des ondes elastiques de surface dans la gamme du MHz sont engendrees et detectees par une technique de laser-ultrasons (acoustique nanoseconde), alors que lacoustique picoseconde est utilisee pour les ondes au GHz. Les echantillons consistent en un arrangement periodique de trous dans un substrat solide (ondes de Rayleigh) ou dans une plaque depaisseur finie(ondes de Lamb). Nous avons mesure des deplacements de surface dans la zone de refraction negative pour differents parametres geometriques du reseau phononique. Nous attribuons ces modes de vibration au repliement des courbes de dispersion induit par la periodicite du milieu. Ces resultats experimentaux seront ensuite compares aux predictions theoriques.
Buckling structures that cannot be simply understood in the frame of continuum elastic theory hav... more Buckling structures that cannot be simply understood in the frame of continuum elastic theory have been observed by atomic force microscopy on gold films, 630 nm thick, deposited by sputtering method on silicon substrates. X-ray diffraction analyses and finite element simulations have been carried out to characterize the stress levels in and around these buckling structures. The high stress concentration
We report on thermal investigations performed in a time resolved experimental scheme. The time do... more We report on thermal investigations performed in a time resolved experimental scheme. The time domain thermoreflectance (TDTR) is applied in an unusual geometry where the pump and probe beams are not superimposed but focused and shifted. In this way, the determination of the in-plane thermal diffusivity is achieved from temperature snapshots at different time delays. In the first part, taking into account the specific generation process and the detection inherent to the time domain thermoreflectance approach, an analytical solution for the temperature field is obtained for bulk samples, and compared to experimental data. A comparison with the frequency domain thermoreflectance microscopy is also outlined. In Part II section, the lateral heat diffusion in a layered structure is investigated. The comparison of the heat diffusion spreading in case of a highly conductive layer deposited on an insulator substrate and the reverse situation are carefully studied. Finally, we show how the time dependence is efficient to probe and identify material thermal properties or thermal interfacial resistance.
We present a new method to measure without any calibration the thermal effusivity, conductivity, ... more We present a new method to measure without any calibration the thermal effusivity, conductivity, and diffusivity of an insulating layer deposited on a substrate, using lateral heat diffusion. The method is applied to Lithium phosphorous oxynitride, a thin film solid-state electrolyte used in micro-batteries.
To characterize the mechanical properties of elastic thin films to improve the lifetime of LMJ co... more To characterize the mechanical properties of elastic thin films to improve the lifetime of LMJ components, two experimental setups have been used: the acoustic picosecond techniques and the Surface Acoustic Wave InterDigital Transducers.
Journal of the Acoustical Society of America, May 1, 2017
The mechanical properties of thin films involved in the manufacturing of ophthalmic glasses have ... more The mechanical properties of thin films involved in the manufacturing of ophthalmic glasses have been investigated by two complementary laser based techniques. On the one hand, picosecond ultrasonics (PU) measurements allows to determine the acoustical longitudinal velocity in the sample, hence the elastic constant c11. On the other hand, Brillouin light scattering (BLS) measurements leads to the value of the transverse velocity, hence c44. In the case of isotropic materials, these two coefficients give a direct access to the value of the Young’s modulus and Poisson’s ratio of the film. The influence of the film characteristics on its mechanical properties will be discussed, mainly regarding its thickness and the manufacturing process. Another issue concerning the effect of the film environment will be addressed. Especially, we will discuss the influence of the substrate on the mechanical properties of a single film, and the link between the mechanical properties of a single film and the ones of a films stacking.
Journal of the Acoustical Society of America, May 1, 2008
In standard ultrafast acoustic experiments very short coherent acoustic pulses are generated by t... more In standard ultrafast acoustic experiments very short coherent acoustic pulses are generated by the absorption of a femtosecond laser pulse in a thin metallic transducer deposited on the sample. Subsequently the acoustic pulses and the heat generated in the transducer cross the sample and are partially transmitted in the underlaying substrate. At low temperature, heating of the metallic transducer gives rise to the emission of incoherent phonons wave packets which propagate ballistically over large distances in the substrate. We report on a series of experiments which demonstrate the acoustic rectification [1-3] of these wave packets as they propagate through large GaAs or Si substrates. [1] B. Perrin, J. de Phys. C8 (1979) 216. [2] S. M. Avanesyan, V. E. Gusev, Solid State. Commun. 54 (1985) 1065. [3] B. Perrin, E. Péronne, L. Belliard, Ultrasonics, 44 (2006) 1277.
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