Single flux quantum elements based on a single-layer of a high-T/sub c/ superconductor

We have designed, fabricated and successfully tested three SFQ elements: a toggle flip-flop, a SFQ voltage amplifier, and an RS-flip-flop. The design uses a single superconducting layer and it is optimized by repeated computer simulations and repeated inductance calculations. The inductances are made as narrow slits of 0.5 /spl mu/m width. Their values are calculated numerically taking into account material parameters derived from experiment. The YBCO junctions are either of step edge type on LaAlO/sub 3/ substrates or located on two closely spaced bi-crystal grain boundaries on a novel YSZ tricrystal substrate. Carbon masks were used to form steps on LaAlO/sub 3/ substrates and for the YBCO patterning. Voltage amplifier shows operation up to 60 K, and both flip-flops were observed to operate at temperatures up to 30 K with parameters close to the simulated values. The operation frequency of a T-flip-flop cell of about 150 GHz was achieved and a new measurement technique of the margins of an RS trigger is suggested.