We have studied the effect of isotopic substitution on the superconducting Tc in the 90-K superconductors Ba2YCu307 and Ba2EuCu307 by replacing ^^O with the heavier isotope '^O. Samples with approximately 75% of the '^O replaced by '^O were prepared by gas-phase ion exchange. In these samples the phonon frequencies, measured by Raman spectroscopy, are reduced by the expected ~4%. The transition temperatures, however, are found to change by less than 0.2%. This change in Tc is much less than that expected for strongly coupled phonon-mediated superconductivity.
It has been observed that ion implantation into Ge at room temperature creates severe surface craters extending several thousand angstroms into the surface, and results in the incorporation of large quantities of C and 0 impurities ( -50 impurities/ion). This effect has a strong temperature dependence and essentially disappears for implantations performed at liquid nitrogen temperature. The systematics of this effect are presented, preliminary annealing results are cited, and possible mechanisms are discussed.
It is shown that strain relaxation during annealing of Si/GexSi1−x/Si heterostructures is significantly enhanced if the strained GexSi1−x layers are implanted with p (B) or n (As) type dopants below the amorphization dose. Comparison of strain relaxation during in situ annealing studies in a transmission electron microscope between unimplanted and implanted structures reveals that the latter show residual strains substantialy below those for unimplanted structures. We propose that this enhanced relaxation is caused by increased dislocation nucleation probabilities due to the high point-defect concentrations arising from implantation.
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