Superconducting and normal metal multilayers of thallium-lead cuprates

We report the growth of c-axis oriented, epitaxial thin films of (Tl,Pb)Sr/sub 2/CuO/sub 5/ on (100) oriented LaAlO/sub 3/ substrates by off-axis sputter deposition in the presence of thallium oxide vapor. These films display a resistivity which crosses over from metallic to semiconducting behavior at low temperature. In addition, we have shown that multiple layers of superconducting (Tl,Pb)Sr/sub 2/Ca/sub 0.8/Y/sub 0.2/Cu/sub 2/O/sub 7/ (1212) and nonsuperconducting (Tl,Pb)Sr/sub 2/CuO/sub 5/ (1201) can be deposited sequentially without compromise of the superconducting properties of the 1212 layer. Bilayers of both 1212 on 1201 and of 1201 on 1212 have been fabricated. In either case, both materials grow with their c-axis normal to the substrate surface and with their a-axes aligned to each other and to the major axes of the substrate. Technologically interesting trilayer structures of 1212/1201/1212 have also been fabricated. Both 1212 layers are superconducting with transition temperatures of up to 94 and 93 K for the upper and lower layers respectively. We believe that this is an important step towards the development of thallium cuprate-based multilayer technology.<
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