Half-Unit Cell Growth of Bi–Sr–Ca–Cu–O Thin Films

Abstract
The growth units of superconducting Bi–Sr–Ca–Cu–O thin films were examined. The films were prepared on Y3Al5O12 (YAG) single-crystal substrates by metalorganic chemical vapor deposition (MOCVD). The growth process of the films at the initial stage was investigated by cross-sectional high-resolution transmission electron microscopy (HREM) and atomic force microscopy (AFM). We found evidence of half-unit cell growth, and the top layer of the half-unit was determined to be a Bi–O layer by angular-resolved measurement using X-ray photoelectron spectroscopy (XPS).