A miniaturized vortex transitional memory cell for a Josephson high-speed RAM

We have developed the smallest Josephson nondestructive read-out (NDRO) memory cell, called a vortex transitional(VT) memory cell, for Josephson high-speed RAM. Its size is 22 mu m*22 mu m, which is only 16% of the size of the previously reported VT memory cells used in Josephson 4-kbit RAM. This was achieved by developing a vertically integrated device structure and refining small-junction technology. The cell consists of Nb/AlOx/Nb junctions, three Nb wirings, SiO/sub 2/ insulators and Mo resistors. The VT memory cells functioned properly, with a large operating margin of +or-20%.<>