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 degreesC and 630 degreesC, 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).