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  • 1995-1999  (3)
  • 62.00  (3)
  • 1
    Electronic Resource
    Electronic Resource
    Mechanical and elastic properties of amorphous hydrogenated silicon films studied by broadband surface acoustic wave spectroscopy (1995)
    Springer
    Applied physics 61 (1995), S. 269-276 
    Details
    ISSN: 1432-0630
    Keywords: 62.00 ; 42.00 ; 68.55
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Mechanical and elastic properties of a-Si∶H films were measured by broadband Surface Acoustic Wave Spectroscopy (SAWS). In the frequency range achieved, the SAW dispersion curves extend to 300 MHz, which allowed the density, Young's modulus, and Poisson's ratio to be evaluated for films grown by laser CVD or plasma CVD with different hydrogen concentrations. The films deposited by either method have the best mechanical and elastic properties. at a hydrogen concentration of about 10 at. %. For this material, a density of (2300±20) kg/m3 and Young's modulus of (134±5) GPa was determined. The network structures of amorphous silicon are discussed by applying the constraint-counting model to estimate the mean coordination number.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01538192
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Theory of photothermal depth profiling via Rayleigh-type surface acoustic wave detection (1995)
    Springer
    Applied physics 61 (1995), S. 299-310 
    Details
    ISSN: 1432-0630
    Keywords: 62.00 ; 65.00 ; 68.00
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract An analytical description is derived for the frequency spectrum of quasi-Rayleigh waves excited thermoelastically by a pulsed laser in a system composed of a solid film on a solid substrate. The relative magnitude of the film and the substrate contributions to the excited quasi-Rayleigh wave depends on their thermoelastic parameters, namely the relative efficiency of photoacoustic conversion in the film and in the substrate, and also significantly on the frequency, because of the redistribution of absorbed laser energy between the film and the substrate through thermal conductivity. Consequently, the frequency spectrum of the surface acoustic wave pulse contains information on the characteristic time of heat conduction in the film and correspondingly on film thickness and the ratio of thermal effusivities of the layer and the substrate. The theory developed should have applications in non-destructive photoacoustic diagnostics of thin films and coatings.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01538195
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Effect of melting on the excitation of surface acoustic wave pulses by UV nanosecond laser pulses in silicon (1995)
    Springer
    Applied physics 61 (1995), S. 285-298 
    Details
    ISSN: 1432-0630
    Keywords: 42.55 ; 43.00 ; 62.00 ; 65.00 ; 68.00
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The influence of melting on the excitation of Surface Acoustic Wave (SAW) pulses in silicon is studied both theoretically and experimentally. The developed theory of Rayleigh-type SAW laser-induced thermoelastic excitation in a structure composed of a liquid layer on a solid substrate predicts that the SAW is predominantly generated in the solid phase due to the absence of shear rigidity in a liquid. The characteristic changes in the SAW pulse shape as well as the saturation and even the decrease of the SAW pulse amplitude observed above the melting threshold are explained theoretically to be a result of the decrease of the heat flux into the solid phase as well as due to the decrease of the volume of the solid phase caused by melting. Although the heat flux into the solid phase is decreased both as a consequence of the reflectivity increase and the additional energy losses (latent heat of melting) at the phase transition, it is demonstrated that the influence of reflectivity changes on the SAW pulse is negligible in comparison with the effect of melt-front motion. For laser pulses of 7 ns duration at 355 nm, the threshold value of laser fluence for meltingF m=0.23±0.04 J/cm2 and for the ablationF a=1.3±0.2 J/cm2 were determined experimentally as the points of characteristic changes in the observed SAW pulses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01538194
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
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