Search

A new design concept is proposed for fabricating rapid single flux quantum (RSFQ) logic circuits. The design approach uses a superconducting layer instead of a superconducting ground plane to increase the geometric size of the RSFQ cell and form narrow slit inductances with width comparable to the London penetration depth. It has been used in the fabrication of a high performance flip-flop cell.

Electron-beam lithography and Ar-ion milling are used to fabricate high-critical temperature, step-edge junction YBCO superconducting quantum interference devices (SQUIDs) on SrTiO3 substrates. The electrical properties and microstructure of the processed SQUIDs are then studied by critical current measurements and scanning electron microscopy. Results show that the SQUIDs emit negligible electromagnetic noise. The devices' step-edge are also very straight, with the YBCO layers growing smoothly over it.

X-ray diffraction and transmission electron microscopy were used to analyze the relation between critical current densitiesand epitaxy of YBaCuO thin films grown on single-crystal MgO and SrTiO substrates. The results revealed that in the MgO substrates, a film with five percent of its grains rotated 45 degrees towards the dominant orientation and exhibited 75% less current density than normal. On the other hand, current density in the SrTiO substrates decreased by 70%. The closer lattice match withSrTiO resulted in higher critical densities.