title: Direct evidence for block-by-block growth in high-temperature superconductor ultrathin films.
abstract: 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 YBa2Cu3O7 cuprate superconductor, using a consistent approach based on the growth of noninteger numbers of YBa2Cu3O7 layers in YBa(2)Cu(3)O(7)/PrBa(2)Cu3O7 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.
authors.affiliation: Departamento Física, Universidad Carlos III de Madrid, Avenida de la Universidad 30, 28911 Leganés, Madrid, Spain.
authors.forename: M
authors.initials: M
authors.lastname: Varela
authors.forename: W
authors.initials: W
authors.lastname: Grogger
authors.forename: D
authors.initials: D
authors.lastname: Arias
authors.forename: Z
authors.initials: Z
authors.lastname: Sefrioui
authors.forename: C
authors.initials: C
authors.lastname: León
authors.forename: C
authors.initials: C
authors.lastname: Ballesteros
authors.forename: K M
authors.initials: KM
authors.lastname: Krishnan
authors.forename: J
authors.initials: J
authors.lastname: Santamaría