SUPERCONDUCTING AND NORMAL-METAL MULTILAYERS OF THALLIUM-LEAD CUPRATES

We report the growth of c-axis oriented, epitaxial thin films of (Tl,P b)Sr2CuO5 on (100) oriented LaAlO3 substrates by off-axis sputter depo sition in the presence of thallium oxide vapor, These films display st resistivity which crosses over from metallic to semiconducting behavi or at low temperature. In addition, we have shown that multiple layers of superconducting (Tl, Pb)Sr2Ca0.8Y0.2Cu2O7 (1212) and nonsupercondu cting (Tl,Pb)Sr2CuO5 (1201) can be deposited sequentially without comp romise of the superconducting properties of the 1212 layer. Bilayers o f both 1212 on 1201 and of 1201 on 1212 have been fabricated. In eithe r 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 a xes of the substrate. Technologically interesting trilayer structures 1212/1201/1212 have also been fabricated. Both 1212 layers are superco nducting with transition temperatures of up to 94 sind 93 K for the up per and lower layers respectively. We believe that this is an importan t step towards the development of thallium cuprate-based multilayer te chnology.