Browsing by Author "Dittrich, Ehrenfried"

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    Satellite phonon absorption lines above the 875 GHz resonance of interstitial oxygen in silicon
    (1987) Dittrich, Ehrenfried; Scheitler, Wolfgang; Eisenmenger, Wolfgang
    Acoustic phonon spectroscopy with superconducting tunneling junctions as phonon generator and detector revealed a large number of sharp absorption lines between 875 GHz (oxygen resonance) and 1.35 THz for silicon doped with interstitial oxygen (Si:0i). The strength of these lines scales with the square of the oxygen concentration ranging from 1017 to 1018 cm-3. Under mechanical stress the lines show a frequency shift almost identical to the main oxygen resonance at 875 GHz as well as to the also observable isotope resonance. These satellite absorption lines are therefore discussed as 0i–0i neighbour interaction. This is supported by the influence of annealing.
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    Spectral dependence of the Kapitza resistance between O,5 K and 2,3 K
    (1984) Koblinger, Otto; Dittrich, Ehrenfried; Heim, Ulrich; Welte, Michael; Eisenmenger, Wolfgang
    Summarizing, we observed strongly enhanced phonon transport from a real solid into 4 He starting at about 85 GHz which is independent of the He gas pressure up to liquid helium. With the isotope 3 He the onset frequency for enhanced phonon transport shifts to 100 GHz. The threshold frequencies are almost independent of the He temperature in the range between 0.5 K and 2.3 K. Only slight shifts to lower frequencies with decreasing He temperature have been observed. No significant influence of the generator material (Sn, Al, SiO) or the generator preparation on the onset frequency has been observed. Moreover at low temperatures and thin He films we observed an additional structure which might be interpreted as film thickness resonances in the He film layer on the generator.