A Rutherford backscattering spectrometry (RBS) study has found that concentrations up to 7at.% of Rb and Cs can be introduced to a depth of ∼700 in MgB2 thin films by annealing in quartz ampoules containing the elemental alkali metals at <350 °C. No significant change in transition temperature (Tc) (determined resistively) was observed, in contrast to an earlier report of very high Tcs (>50K) from susceptibility measurements on MgB2 powders. The lack of a significant change in Tc and intra-granular carrier scattering suggests that Rb and Cs diffuse into the film, but do not enter the grains. Instead, the observed changes in the electrical properties, including a significant drop in J c and an increase in Δρ(ρ300- ρ40), arise from a decrease in inter-granular connectivity due to segregation of the heavy alkaline metals and other impurities (i.e.C and O) introduced into the grain boundary regions during the anneals.

Original languageEnglish (US)
Article number025012
JournalSuperconductor Science and Technology
Issue number2
Publication statusPublished - Feb 1 2008


ASJC Scopus subject areas

  • Physics and Astronomy (miscellaneous)
  • Condensed Matter Physics
  • Electronic, Optical and Magnetic Materials

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