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

Abstract

To resolve the long-standing but fundamental issue of growth modes, a consistent approach based on ex situ quantitative structural and chemical characterization of epitaxially grown ultrathin layers in YBCO/PBCO superlattices was developed. From the analysis of superlattices with a noninteger number of YBCO layers, concrete evidence was obtained for a two dimensional block-by-block growth mechanism in which the growth units are single YBCO unit cells and layer growth proceeds laterally, by the addition of one unit cell blocks.