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  • 1
    Electronic Resource
    Electronic Resource
    Analysis of excitation and coherent amplitude enhancement of surface acoustic waves by the phase velocity scanning method (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 6511-6522 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present a general theoretical formulation for the characteristics of surface acoustic waves (SAW) generated by the phase velocity scanning (PVS) method that employs a scanning single laser beam (SSB) or a scanning interference fringes (SIF). In the SSB approach, a broad band SAW pulse is generated and its amplitude is coherently enhanced when the laser scanning velocity V is equal to the phase velocity νR of the SAW. The amplitude of the SAW follows a resonance curve represented by a sinc function of the scanning velocity V, but different spatial frequency components in the SSB significantly suppress the side lobes of the resonance curve. In the SIF approach, the scanning velocity νf of the fringes is determined by the intersection angle and the frequency difference ωa of the laser beams. A narrow band tone burst of SAW with frequencies higher than 100 MHz can be excited. The SAW frequency ω depends upon a characteristic time t*, defined as a propagation time of the SAW across the laser beam spot. The SAW frequency ω is identical to the frequency difference ωa when the laser pulse width T is longer than the characteristic time t*. But, the SAW frequency ω is determined as a product kfνR of the wave number of the SIF and the SAW velocity when the laser pulse width is shorter than the characteristic time. Precise frequency measurement provided by the amplitude enhancement effect and the narrow frequency bandwidth in the SIF approach make the PVS method particularly promising for the noncontact SAW velocity measurement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355140
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  • 2
    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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  • 3
    Electronic Resource
    Electronic Resource
    Measurement of debonding in cracked nanocomposite films by ultrasonic force microscopy (2002)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 80 (2002), S. 1180-1182 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This letter reports the application of ultrasonic force microscopy (UFM) to investigate subsurface fracture mechanisms during tensile loading of nanocomposite films consisting of a brittle glass on a ductile polyethylene terephthalate (PET) substrate. Such materials are used in packaging applications where a gas barrier is required to maintain the product quality. Cracking or debonding of the surface glass layer results in destruction of the gas barrier properties of the film. Accurate evaluation of the continuity or discontinuity at the crack edge within the layered material is crucial for the correct characterization of both adhesive failure and crack propagation. Here simultaneous atomic force microscopy and UFM images are compared for a range of tensile strains to identify debonded regions of the glass film from the PET. Debonding occurred for strains greater than 6%. In some films, this debonding increased with applied strain. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1450058
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  • 4
    Electronic Resource
    Electronic Resource
    Ultrasound induced lubricity in microscopic contact (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 71 (1997), S. 1177-1179 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A physical effect of ultrasound induced lubricity is reported. We studied the dynamic friction dependence on out-of-plane ultrasonic vibration of a sample using friction force microscopy and a scanning probe technique, the ultrasonic force microscope, which can probe the dynamics of the tip–sample elastic contact at a submicrosecond scale. The results show that friction vanishes when the tip–surface contact breaks for part of the out-of-plane vibration cycle. Moreover, the friction force reduces well before such a break, and this reduction does not depend on the normal load. This suggests the presence on the surface of a layer with viscoelastic behavior. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.120417
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