Bell Communications Research, Inc.

Arun Inam

Ramamoorthy Ramesh

Charles T Rogers, Jr

Thirumalai Venky Venkatesan

Manjanath S Hegde

A method, and the resulting structure, of growing a superconducting perovskite thin film of, for example YBa.sub.2 Cu.sub.3 O.sub.7-x. A buffer layer of, for example, the perovskite PrBa.sub.2 Cu.sub.3 O.sub.7-y, is grown on a crystalline (001) substrate under conditions which favor growth of a,b-axis oriented material. Then the YBa.sub.2 Cu.sub.3 O.sub.7-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 YBa.sub.2 Cu.sub.3 O.sub.7-x, which nonetheless shows a superconducting transition temperature near that of c-axis oriented films.

Growth of a,b-axis oriented pervoskite thin films

A method, and the resulting structure, of growing a superconducting perovskite thin film of, for example, YBa.sub.2 Cu.sub.3 O.sub.7-x. A buffer layer of, for example, the perovskite PrBa.sub.2 Cu.sub.3 O.sub.7-y, is grown on a crystalline (001) substrate under conditions which favor growth of a,b-axis oriented material. Then the YBa.sub.2 Cu.sub.3 O.sub.7-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 YBa.sub.2 Cu.sub.3 O.sub.7-x, which nonetheless shows a superconducting transition temperature near that of c-axis oriented films.

Growth of a,b-axis oriented perovskite thin films over a buffer/template

A ferroelectric memory and its method of making in which a highly c-axis oriented layer (56) of ferroelectric lead zirconate titanate (PZT) is epitaxially deposited at between 640.degree. and 710.degree. C. upon a crystalline film (54) of yttrium barium copper oxide (YBCO), acting both as growth template and bottom electrode. A top electrode (58) is formed over the ferroelectric layer to complete the memory element. The two electrodes are preferably composed of the same perovskite conductor of the same cyrstalline orientation, most preferably, a-axis oriented YBCO. The structure can be grown on a silicon substrate (50) with an intermediate buffer layer (52) of yttria-stabilized zirconia. The ferroelectric behavior is optimized if the structure is cooled from its growth temperature at about 20.degree. C./min. Such a-axis oriented perovskite thin films can be grown by continuously depositing the same or different perovskite material, but dividing the deposition into three temperature stages, a first at a temperature favoring a-axis oriented growth, a second gradually increasing the temperature to a temperature favoring c-axis growth, and a third at the c-axis growth temperature. Nonetheless, a high-quality a-axis oriented film is grown. The memory can be rejuvenated after it has become fatigued by applying a pulse of magnitude equal to that of the writing pulse but of considerably longer duration.

Crystallographically aligned ferroelectric films usable in memories and

A superconducting device and method of making in which a superconducting YBaCuO layer is laser deposited on a SrTiO.sub.3 or similar substrate such that the c-axis of the YBaCuO layer is vertically aligned with that of the substrate. A non-superconducting layer of PrBaCuO or MgO is laser deposited on the superconducting layer and another superconducting YBaCuO layer is laser deposited on the non-superconducting layer with the c-axes of all the layers being aligned. Contacts are applied to the two superconducting layers to form a junction device across the non-superconducting layer, which acts as a barrier layer.

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Arun Inam