Direct evidence for negative grain boundary potential in Ca-doped and undoped YBa2Cu3O7-x |
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Authors: | Schofield Marvin A Beleggia Marco Zhu Yimei Guth Karsten Jooss Christian |
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Institution: | Brookhaven National Laboratory, Upton, New York 11973, USA. schofield@bnl.gov |
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Abstract: | Using electron holography in a transmission electron microscope, we obtained direct evidence for the reduction of negative charge at grain boundary dislocations in Ca-doped YBa2Cu3O7 (YBCO) when compared to undoped YBCO. Because of the finite width of the valence band in the superconducting CuO2 planes, the negative grain boundary charge can lead to a depletion of electron holes available for superconductivity. A significant reduction in the size of the perturbed region in the Ca-doped samples appears to be the principal mechanism for the improved interfacial superconductivity. |
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