Direct evidence for negative grain boundary potential in Ca-doped and undoped YBa2Cu3O7-x.
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.
Schofield
Marvin A
MA
Brookhaven National Laboratory, Upton, New York 11973, USA. schofield@bnl.gov
Beleggia
Marco
M
Zhu
Yimei
Y
Guth
Karsten
K
Jooss
Christian
C