Investigation of YBCO film growth by post-annealing of precursor films including BaF2 at low-pressure oxygen atmosphere

Precursor films were deposited by the co-evaporation technique using Y, BaF2 and Cu as evaporation sources. Then, the films were annealed at low-pressure oxygen atmosphere without the introduction of water vapour, which was different from the so-called BaF2 ex situ process. Previous studies have indicated that the c-axis-oriented YBCO films can be prepared by annealing at low-pressure oxygen atmosphere, and that the reaction of the precursor films during sample temperature elevation is very important in the present process according to reflection high-energy electron diffraction (RHEED) observation. Therefore, two kinds of samples, rapidly cooled down from 400 deg. C and 630 deg. C, were prepared for microstructural study. YBCO film growth in this process is discussed on the basis of the results of x-ray diffraction (XRD), RHEED and transmission electron microscopy (TEM). (author)