MICROSTRUCTURES OF ALPHA-AXIS ORIENTED YBCO FILMS MADE BY HYBRID PLASMA SPUTTERING

Microstructures of a-axis oriented YBa2Cu3O7-x, films made by newly de veloped de 100 MHz hybrid plasma sputtering were investigated using tr ansmission electron microscopy (TEM). The films deposited on (110) NdG aO3 and (100) SrTiO3 substrates were found to grow in a perfect epitax ial fashion and with clear interface. The plan view of the TEM image s howed that both films were comprised of two kinds of grains having the c axis aligning along two perpendicular directions in the plane with equal probability. The structures of the grain boundary, however, were found to be very different for the two films from the plan views. The film on NdGaO3 showed a lot of twist boundaries, while the film on Sr TiO3 consisted of many symmetrical tilt boundaries and basal-plane-fac ed tilt boundaries. The type of grain boundary is determined by the an isotropic growth rates of the film between c direction and a-b directi on.