High rate deposition of 5 /spl mu/m thick YBa/sub 2/Cu/sub 3/O/sub 7/ films using the BaF/sub 2/ ex-situ post annealing process
We have investigated the crystallization of thick YBCO films under various annealing conditions. The films were deposited by high-rate co-evaporation of Y, Cu and BaF/sub 2/ onto room-temperature SrTiO/sub 3/ substrates at rates exceeding 10 nm/s. TEM microscopy was performed to establish the microscopic structure of partially processed films and help elucidate the growth mechanism. In-situ resistivity measurements were used to monitor the crystallization of the YBCO films during the annealing process. Resistivity measurements and TEM microscopy of samples at different stages of the film growth are compared. Our results indicate that, in addition to oxygen partial pressure, water vapor pressure is an important parameter which defines the dynamics of film growth and crystallization. 5 /spl mu/m thick films with J/sub c/>2/spl times/10/sup 5/ A/cm/sup 2/ (1 T H/spl par/c) have been fabricated.