Edge-junction type nanometer bridge

An edge-junction type nm (nanometer) bridge is fabricated which has bridges on the joint of the edges of two Nb films. Each nm bridge has an effective length of less than 50 nm, width about 2 μm, and thickness from 30 to 60 nm. To make a good edge-junction type nm bridge, it is necessary to form a sharp edge on an Nb film. For this purpose, dry-etching with a teflon holder in an He gas was used. Voltage steps up to about about 100 μV induced by a microwave were observed in the fabricated device, and the value of IORn greater than 50 μV was obtained. By measuring the threshold characteristic of a DC-SQUID consisting of this nm bridge, it was confirmed that the current-phase relation of the bridge is sinusoidal. The temperature range in which this sinusoidal relation is kept is as wide as 4 to 6 K approximately.