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Strukturelle Charakterisierung und Optimierung der Beugungseigenschaften von Si(1-x)Ge(x) Gradientenkristallen, die aus der Gasphase gezogen wurden

Journal Article


Abstract


  • Two theoretical models for the description of the diffraction properties of

    gradient crystals have been developed, one in the framework of the kinematic

    theory, the other within a transfer matrix formalism based on the dynamical

    theory of diffraction. A matrix describes the coupling and the propagation of

    the forward- and the Bragg-diffracted wave functions through a plane, parallel

    crystal lamella. It applies for the description of any crystalline medium with

    changes of the diffraction properties along the direction of the surface

    normal. Experimentally a crystal growth technique has been set up to produce

    novel Si1-xGex gradient crystals with 0 < x < 0.4 on a large surface and with

    growth rates of up to 0.6 um/min. Layer thicknesses of several 100 um have been

    achieved. A tetragonal distortion attributed to different thermal expansion

    coefficients has been discovered. The anisotrope mosaic distribution gives

    evidences for the existence of misfit dislocations. The reflection curves

    calculated by the transfer matrix method fit well the experimental results. The

    diffraction data show an intensity increase of 25 related to the experimental

    resolution function. Comparing this value with the calculated reflectivity for

    perfect silicon, this factor increases to 40.

Publication Date


  • 2018

Web Of Science Accession Number


Abstract


  • Two theoretical models for the description of the diffraction properties of

    gradient crystals have been developed, one in the framework of the kinematic

    theory, the other within a transfer matrix formalism based on the dynamical

    theory of diffraction. A matrix describes the coupling and the propagation of

    the forward- and the Bragg-diffracted wave functions through a plane, parallel

    crystal lamella. It applies for the description of any crystalline medium with

    changes of the diffraction properties along the direction of the surface

    normal. Experimentally a crystal growth technique has been set up to produce

    novel Si1-xGex gradient crystals with 0 < x < 0.4 on a large surface and with

    growth rates of up to 0.6 um/min. Layer thicknesses of several 100 um have been

    achieved. A tetragonal distortion attributed to different thermal expansion

    coefficients has been discovered. The anisotrope mosaic distribution gives

    evidences for the existence of misfit dislocations. The reflection curves

    calculated by the transfer matrix method fit well the experimental results. The

    diffraction data show an intensity increase of 25 related to the experimental

    resolution function. Comparing this value with the calculated reflectivity for

    perfect silicon, this factor increases to 40.

Publication Date


  • 2018

Web Of Science Accession Number