PHASE-TRANSFORMATIONS IN Y1BA2CU3O7-X FILMS PREPARED BY PULSED LASER DEPOSITION

Phase transformations are investigated in Y1Ba2Cu3O(y) films prepared by pulsed laser deposition on Al2O3 and (111)Si substrates overcoated with a ZrO2 sublayer 0 to 60 nm thick. The films are deposited at substrate temperatures within 400 to 1173 K in an oxygen atomosphere with P(o2) = 10(-1) to 10(-4) Pa and cooled at oxygen pressures P(o2) = 10(-1) or 10(5) Pa. It is demonstrated that the substrate temperature and the oxygen pressure during both, deposition and cooling have a considerable effect on the sequence of phase transformations in the films. It is found that the concentration of oxygen dissolved in the film is the limiting parameter of the tetragonal-to-orthorhombic phase transition and the condensed film thickness is the parameter affecting the temperature of nucleation of the 1:2:3 phase.