THERMODYNAMICS AND FABRICATION OF EPITAXIAL PB(ZR,TI)O-3 (PZT) THIN-FILMS

Up to now, an epitaxial PZT thin him in which the tetragonal and rhomb ohedral phases coexist has not been successfully obtained. We have con sidered the reason behind the observed difficulty in the fabrication o f this type of thin films and developed a new thermodynamic model for an epitaxial ferroelectric thin film under a two-dimensional compressi ve stress. This thermodynamic formalism predicts a shift of the morpho tropic phase boundary towards the rhombohedral-phase field under the s tress so as to explain the observed difficulty in the fabrication. We have experimentally proved this prediction by fabricating an epitaxial ly oriented tetragonal PZT thin film on MgO substrate with the target composition corresponding to the bulk MPB composition (i.e., Zr/Ti app roximate to 52/48).