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  • 1
    Electronic Resource
    Electronic Resource
    Thermal diffusivity of anisotropic materials by photothermal methods (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 3984-3993 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this paper we analyze the possibility of extending the photothermal methods developed for thermal diffusivity measurements of isotropic materials [A. Salazar and A. Sánchez-Lavega, Rev. Sci. Instrum. 65, 2896 (1994)] to the case of anisotropic specimens. A full theoretical treatment of the photothermal signal generation for the case of an anisotropic sample with its principal axes aligned with the sample surface is presented. Three photothermal detection schemes have been studied: infrared radiometry, photothermal reflectance, and optical beam deflection (mirage effect). The fundamental result we have obtained is that when using infrared radiometry, photothermal reflectance and collinear mirage setups, the thermal magnitude retrieved is the resistivity to heat diffusion (a tensor defined as the inverse of the thermal diffusivity tensor). Only the perpendicular mirage experiment allows one to directly retrieve the thermal diffusivity along any direction of the material. Experimental measurements performed on two highly anisotropic materials confirm the above-mentioned results. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361827
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  • 2
    Electronic Resource
    Electronic Resource
    Photothermal microscopy: Thermal contrast at grain interface in sintered metallic materials (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 3344-3350 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A theoretical and experimental study of the influence of planar thermal barriers on photothermal reflectance microscopy signals is presented. An analytical solution is developed for the problem of vertical barriers in a semi-infinite solid and the signal contrast obtained when scanning through the barrier is discussed as a function of the thermal resistance, the thermal diffusion length, and the pump and probe beam dimensions. The shape and the width of the signal perturbation introduced by the barrier is also analyzed. For the case of slanted barriers results of finite-element calculations are presented, and the main feature of the signal when going from vertical to slanted barriers is thus shown. Finally, the theoretical predictions are compared with measurements made on Fe sintered samples. Scanning through grain interfaces revealed different signal shapes and contrast. Good agreement between theory and experiment was found when the optical contrast at the interface is negligible. Examples are shown where the thermal barrier model is no longer valid and an extended model seems to be necessary.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356119
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  • 3
    Electronic Resource
    Electronic Resource
    Photothermal characterization of vertical and slanted thermal barriers: A quantitative comparison of mirage, thermoreflectance, and infrared radiometry (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 2968-2982 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present a quantitative and comparative study of three different photothermal techniques based on the signal produced on vertical/slanted thermal barriers under a variety of barrier/sample conditions. Models based on integral methods are developed to calculate the amplitude and phase of the sample surface temperature and mirage deflection in surrounding air. The geometries studied include: vertical, tilted, buried, and finite size barriers separating identical or different media. The models incorporate the probe and pump beam sizes, the thermal resistance of the barrier and the optothermal characteristics of the sample. Experimental measurements are performed on a variety of fabricated barriers with three modulated photothermal techniques: the thermoreflectance, infrared radiometry, and mirage detection. We discuss in a comparative way the limits, drawbacks and the applicability of each technique. Model fits to the experimental results allow characterization of the thermal barrier (spatial localization, geometry, orientation, and size) and provide an accurate determination of its thermal resistance. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363154
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  • 4
    Electronic Resource
    Electronic Resource
    Compact design for real time in situ atmospheric trace gas detection based on mirage effect (photothermal deflection) spectroscopy (1996)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 67 (1996), S. 1891-1895 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We present a compact and rugged setup for real time in situ trace gas detection based on photothermal deflection spectroscopy. The use of high quality Ge windows permits a true parallel geometry, resulting in a design resistant to ambient air motion while preserving the advantages of the technique such as good sensitivity, local probing, and open air measurement capability. Detection of ethylene within an enclosed sample cell has been performed in a N2 atmosphere, and we estimate the practical noise limited detection minimum to be 250 ppt, an order of magnitude improvement from a previous setup. We have measured absorption spectra of open laboratory air and real time ethylene exhaust from polymer and biological samples to investigate indus- trial, agricultural, and environmental applications. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146994
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  • 5
    Electronic Resource
    Electronic Resource
    Nondestructive control of weldings using the mirage detection (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 57 (1985), S. 1009-1015 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Small defects in edge-to-edge weldings of thin pieces of stainless steel have been detected by the mirage effect. A simple 1D theoretical model shows the physical parameters influencing the experimental results. Using the phase of both the transverse and normal deviations at various frequencies allows for the separation of optical and thermal effects, of surface and subsurface defects, and for the determination of the depths and widths of the subsurface defects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.334540
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  • 6
    Electronic Resource
    Electronic Resource
    Near-field optical spectroscopy using an incoherent light source (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 76 (2000), S. 397-399 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present a method to perform near-field optical spectroscopy. It consists of an apertureless near-field optical microscope combined with an incoherent light source and a monochromator. We show that the optical response of the tip depends both on the wavelength and the tip apex shape. The experimental optical response of the tips is in good agreement with the predicted theoretical one. The near-field optical spectrum obtained on a gold island in the visible spectrum range (λ=400–600 nm) is presented and shows that the method is reliable to perform spectroscopic measurements on submicrometer-sized objects. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.125766
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  • 7
    Electronic Resource
    Electronic Resource
    Novel results on thermal diffusivity measurements on anisotropic materials using photothermal methods (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 626-628 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have applied two photothermal techniques (infrared radiometry and mirage) and conventional procedures to measure the thermal diffusivity of a highly anisotropic sample of pyrolytic graphite. Unexpected and strongly differing results are obtained with each technique. A theoretical analysis indicates that whereas the mirage technique gives a measure of the elements of the thermal diffusivity tensor, infrared radiometry yields the elements of another thermal magnitude represented by the inverse of this tensor. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.115410
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  • 8
    Electronic Resource
    Electronic Resource
    Photothermal imaging of copper-decorated grain boundary in silicon (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 56 (1990), S. 1749-1751 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Using a scanning photothermal reflectance microscope we have observed a large enhancement of the modulated reflectance signal accompanied by a phase change of π in the region of a copper-decorated grain boundary in silicon. A preliminary analysis of the data is given in terms of the thermal and plasma waves generated in the specimen. Orders of magnitude of recombination velocities of the surface and the boundary are determined in reasonable agreement with electrical measurements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.103088
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  • 9
    Electronic Resource
    Electronic Resource
    Infrared near-field imaging of implanted semiconductors: Evidence of a pure dielectric contrast (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 71 (1997), S. 575-577 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this letter, we demonstrate the ability of our reflection mode scanning near-field optical microscope functioning in the mid-infrared to reveal infrared dielectric contrast in absence of any topographical contrast. This contrast is induced by local structures prepared by low energy boron implantation in silicon. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.119798
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  • 10
    Electronic Resource
    Electronic Resource
    Temperature field determination of InGaAsP/InP lasers by photothermal microscopy: Evidence for weak nonradiative processes at the facets (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 4-6 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Photothermal microscopy was used for absolute temperature determination of InGaAsP/InP lasers. High modulation frequencies were employed in order to improve spatial contrast. The strong thermal mismatch between InGaAsP and InP induces a heat confinement in the active region as shown experimentally and confirmed by finite element calculations. Facet temperature was found to be 10 K/mW for a 2-μm-wide active layer, which is low compared to those reported for GaAlAs/GaAs and GaInP. Moreover, measurements along the cavity do not show differences in temperature when approaching the facets. Both results indicate a weak nonradiative recombination process at the facets, in agreement with the higher mirror reliability of this type of laser.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.110918
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