Effect of Rb and Cs doping on superconducting properties of MgB2 thin films

Rakesh Singh; Y. Shen; R. Gandikota; D. Wright; C. Carvalho; J. M. Rowell; Nathan Newman

doi:10.1088/0953-2048/21/2/025012

Effect of Rb and Cs doping on superconducting properties of MgB₂ thin films

Rakesh Singh, Y. Shen, R. Gandikota, D. Wright, C. Carvalho, J. M. Rowell, Nathan Newman

Research output: Contribution to journal › Article › peer-review

1 Scopus citations

Abstract

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 (T_c) (determined resistively) was observed, in contrast to an earlier report of very high T_cs (>50K) from susceptibility measurements on MgB₂ powders. The lack of a significant change in T_c 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 language	English (US)
Article number	025012
Journal	Superconductor Science and Technology
Volume	21
Issue number	2
DOIs	https://doi.org/10.1088/0953-2048/21/2/025012
State	Published - Feb 1 2008

ASJC Scopus subject areas

Ceramics and Composites
Condensed Matter Physics
Metals and Alloys
Electrical and Electronic Engineering
Materials Chemistry

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title = "Effect of Rb and Cs doping on superconducting properties of MgB2 thin films",

abstract = "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.",

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AU - Singh, Rakesh

AU - Shen, Y.

AU - Gandikota, R.

AU - Wright, D.

AU - Carvalho, C.

AU - Rowell, J. M.

AU - Newman, Nathan

PY - 2008/2/1

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N2 - 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.

AB - 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.

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Effect of Rb and Cs doping on superconducting properties of MgB₂ thin films

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