Microstructures of sputtered oriented Si/CeO2 bi-layers for YBa2Cu3O7-d/Si integrated microelectronics

In the framework of a research aimed to superconductor/semiconductor integrated electronics, we have grown a-axis oriented YBCO thin films on silicon (100) substrates with (111) oriented insulating buffer layers of cerium dioxide (CeO2), using magnetron sputtering deposition techniques. The properties of the cerium dioxide layer have been preliminary optimized by means of several layout and by monitoring the growing procedures through X-ray diffraction, AFM and TEM techniques. The lattice matching between CeO2 and YBCO resulted to be worsened by an amorphous thin SiO2 layer at the Si/CeO2 interface, that decouples the buffer orientation from the seed orientation. However, it was possible to grow a relatively thick, optimally textured layer of CeO2 wothout spurious orientations. The YBCO films deposited on top of this layer result preferentially a-axis oriented. The transition widths are very large, but well controllable and reproducible. Some technological applications can be already envisaged.