Crystallographically Aligned Ferroelectric Films Usable in Memories and Method of Crystallographically Aligning Perovskite Films

GROWTH OF A,B-AXIS ORIENTED PEROVSKITE THIN FILMS

A method, and the resulting structure, of growing a superconducting perovskite thin film of, for example, YBa2Cu3O7-x. A buffer layer of, for example, the perovskite PrBa2Cu3O7-y, is grown on a crystalline (001) substrate under conditions which favor growth of a,b-axis oriented material. Then the YBa2Cu3O7-x layer is deposited on the buffer layer under changed growth conditions that favor growth of c-axis oriented material on the substrate, for example, the substrate temperature is raised by 110.degree.C. However, the buffer layer acts as a template that forces the growth of a,b-axis YBa2Cu3O7-x, which nonetheless shows a superconducting transition temperature near that of c-axis oriented films.

CRYSTALLOGRAPHICALLY ALIGNED FERROELECTRIC FILMS USABLE IN MEMORIES AND METHOD OF CRYSTALLOGRAPHICALLY ALIGNING PEROVSKITE FILMS

A ferroelectric memory and its method of making in which a highly c-axis oriented layer of ferroelectric lead zirconate titanate (PZT) is epitaxially dep osited at between 640.degree. and 710.degree.C upon a crystalline film of yttrium barium c opper oxide (YBCO), acting both as growth template and bottom electrode. A top electrode is formed o ver the ferroelectric layer to complete the memory element. The two electrodes are prefe rably composed of the same perovskite conductor of the same crystalline orientation, m ost preferably, .alpha.-axis oriented YBCO. The structure can be grown on a silicon substrate with an intermediate buffer layer of yttria-stabilized zirconia. The ferroelectric be havior is optimized if the structure is cooled from its growth temperature at about 20.deg ree.C/min. Such a-axis oriented perovskite thin films can be grown by continuously depositing th e same or different perovskite material, but dividing the deposition into three temperatur e stages, a first at ...