Fabrication of high-Tc superconducting multilayer structure with YBa2Cu3O7 − x thin films separated by SrTiO3 interlayers

• Superconducting YBa2Cu3O7 − x thin films were deposited in the multilayer structure.
• Sandwiching of YBa2Cu3O7 − x thin films in between SrTiO3 layers
• Sandwiching was found to enhance the superconducting transition temperatures.
• Microbridge structure was patterned on the top layer of YBa2Cu3O7 − x thin film stack.
• The characteristics of the microbridge were found to be satisfying the expectations.

Multilayer thin film structures are attractive for superconducting microelectronics, but they are difficult to achieve on high Tc superconductors such as YBa2Cu3O7 − 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 SrTiO3 (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.