Fabrication of high-T_c superconducting multilayer structure with YBa_2Cu_3O_(7-x) thin films separated by SrTiO_3 interlayers

摘要

Multilayer thin film structures are attractive for superconducting microelectronics, but they are difficult to achieve on high T_c superconductors such as YBa_2Cu_3O_(7-x) (YBCO) thin films. The conventional process has been based on fabricating the YBCO thin films on multiple buffer layers resulting in a single superconducting upper layer on a multilayer-type structure; here we present a full fabrication process for the growth of a multilayer superconducting thin film structure that contains multiple superconducting YBCO thin film layers separated by SrTiO_3 (STO) interlayers in sandwich-type configuration. The deposition process was optimized for dc and rf magnetron sputtering techniques for the deposition of YBCO and STO thin films respectively. An YBCO/STO/ YBCO/STO/YBCO type configuration was fabricated on a commercial single crystal (100) STO substrate by precisely tuning the deposition process parameters. Superconducting properties of YBCO layers were tested by ac magnetic susceptibility and resistances versus temperature measurements after the deposition of each additional layer. In order to demonstrate potential device application, a microbridge pattern was fabricated onto the top YBCO layer and current-voltage analysis was performed.