Direct evidence for block-by-block growth in high-temperature superconductor ultrathin films

© 2001 The American Physical Society. M. V. was partially supported by a research grant of the Fundación Universidad Carlos III de Madrid. Financial support from CICYT Grant No. MAT99-1706E is also acknowledged. M. V. is thankful for the hospitality received during her stay at the LBNL/NCEM. W. G. acknowledges support from the Max Kade Foundation for his stay at Berkeley. Work at LBNL/NCEM was supported by the Director, Office of Energy Research, Office of Basic Energy Sciences, Materials Sciences Division of the U.S. Department of Energy under Contract No. DE-AC03-76SF00098.
Charge neutrality and stoichiometry impose severe restrictions on the mechanisms of epitaxial growth of complex oxides. The fundamental question arises of what is the minimum growth unit when sample thickness is reduced beyond the size of the unit cell. We have investigated the growth mechanism of YBa_(2)Cu_(3)O_(7) cuprate superconductor, using a consistent approach based on the growth of noninteger numbers of YBa_(2)Cu_(3)O_(7) layers in YBa_(2)Cu_(3)O_(7)/PrBa_(2)Cu_(3)O_(7) superlattices. Ex situ chemical and structural analysis evidence a 2D block-by-block mechanism in which the minimum growth units are complete unit cell blocks, growing coherently over large lateral distances.
Fundación Universidad Carlos III de Madrid
CICYT
Max Kade Foundation
Director, Office of Energy Research, Office of Basic Energy Sciences, Materials Sciences Division of the U.S. Department of Energy
Depto. de Estructura de la Materia, Física Térmica y Electrónica
Fac. de Ciencias Físicas
TRUE
pub