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  • 1
    Electronic Resource
    Electronic Resource
    Resonant electromagnetic excitation and detection of ultrasonic waves in thin sheets (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 4830-4839 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A unified theory of the simultaneous electromagnetic excitation and detection of ultrasonic waves travelling in the through-thickness direction in conducting sheets in the presence of a static magnetic field is presented. What to our knowledge are the highest-frequency room-temperature measurements of this type are described for aluminium sheets of thickness as low as 20 μm for frequencies up to 120 MHz. Maxwell's equations are solved for the geometry of a planar current sheet above a conducting sheet with sinusoidal time variation. It is shown how, from the solution of a single fourth-order differential equation for the magnetic vector potential, the coupled electromagnetic and elastic wave problem can be solved analytically. The effective transfer impedance is evaluated, a measure of the ultimate efficiency of the combined excitation and detection process. At acoustic resonance its amplitude is inversely proportional to the sum of the ultrasonic attenuation of the sample and the attenuation arising from the electromagnetic-elastic coupling. This high-frequency resonant method should open up a wide range of new applications for the nondestructive evaluation of thickness, ultrasonic attenuation, bonding, and delamination of thin sheets and coatings in the sub-10 μm to 1 mm thickness range.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352047
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Thickness and sound velocity measurement in thin transparent films with laser picosecond acoustics (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 1617-1629 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A new thin-film optical testing method is described for both thickness and sound velocity of transparent films on opaque substrates with laser picosecond acoustics using the optical pump-probe technique. The theory of excitation and detection of ultrasonic stress pulses for this geometry is presented in detail together with experimental results for sputtered thin films of silica of thickness 200 nm–2 μm on amorphous germanium substrates. Reflectance variations, measured as a function of pump-probe delay time, are characterized by echoes and beating oscillations superimposed on periodic steplike changes. These effects are modeled as a sum of an echo contribution from the stress-induced modulation of the substrate reflectance, an interference contribution from the light reflected by the moving stress pulse in the transparent film, a contribution from the modulation of the light on transmission through this stress pulse, and a contribution from the stress-induced ultrafast vibrations of the film interfaces of order 10−3 nm. The latter contribution arises from thin-film interference effects that represent a novel detection mechanism for surface vibrations in the picosecond regime. Sound velocity and thickness are derived from the data to an accuracy of a few percent, and the photoelastic constant of the transparent film is determined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351218
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Photothermal probing of inhomogeneously modulated transparent thin films (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 5002-5009 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The problem of the photothermal modulation of optical beams passing through multilayer films is an extremely complex one owing to the inhomogeneously modulated refractive index combined with multiple optical reflections inside the sample. This problem has so far not been given an exact analytical treatment in the field of photothermal probing. We consider here such a treatment for normal-incidence optical probing in reflectance of photothermally modulated single-layer thin-film samples with arbitrary optical constants. The validity of the method is demonstrated by application to a thin transparent film of silica on a silicon substrate. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1462414
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  • 4
    Electronic Resource
    Electronic Resource
    Waveguide ultrasonic force microscopy at 60 MHz (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 76 (2000), S. 1836-1838 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present measurements using ultrasonic force microscopy at ∼60 MHz, operating in a "waveguide" mode in which the cantilever base is vibrated and flexural ultrasonic vibrations are launched down the cantilever without exciting any particular cantilever resonance. The nonlinearity of the tip-sample force-distance curve allows the conversion of a modulated ultrasonic frequency into a low frequency vibration of the cantilever, detected in a conventional atomic force microscope. Images of Ge quantum dots on a Si substrate show contrast related to elasticity and adhesion differences, and this is interpreted with the Johnson–Kendall–Roberts model of the force-distance curve. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.126184
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  • 5
    Electronic Resource
    Electronic Resource
    Hysteresis of the cantilever shift in ultrasonic force microscopy (2002)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 80 (2002), S. 2386-2388 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We propose a technique based on ultrasonic force microscopy that exploits the hysteresis in cantilever jumping to and from a sample while varying the ultrasonic amplitude. Both the elastic modulus and the work of adhesion can be determined by comparision with a relation derived between their ratio and the cantilever shift at the jump-in point. The method is applied to measurements on an aluminum thin film. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1463212
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  • 6
    Electronic Resource
    Electronic Resource
    Picosecond relaxation and thermal diffusion in amorphous silicon (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 553-555 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have studied the time-resolved reflectivity changes in the picosecond–nanosecond range induced by picosecond visible optical pulses in ion-implanted amorphous silicon-on-sapphire. Illumination from the front side of the thin film probes the picosecond carrier relaxation processes. Heat release from trapped carriers in the 100-ps range is shown to be significant. Illumination from the substrate side probes, in addition, the ultrafast diffusion of heat to the substrate. The derived thermal diffusivity is shown to correspond to a near-surface layer much thinner than the optical absorption depth. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.117784
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    Paper (German National Licenses)
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  • 7
    Electronic Resource
    Electronic Resource
    Acoustic generation in crystalline silicon with femtosecond optical pulses (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 1190-1192 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Volume contraction in bulk silicon crystals is observed on excitation with femtosecond visible optical pulses. The surface deformation and generated acoustic strain are measured using detection based on both probe beam reflectivity changes and probe beam deflection. The contraction is explained by the dominant electronic contribution to the strain from excitation of electron-hole pairs, which swamps the thermoelastic expansion. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.113853
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