ADJUSTABLE NANOFABRICATED ATOMIC SIZE CONTACTS

Metallic point contacts and tunnel junctions with a small and adjustab le number of conduction channels have been obtained in the last few ye ars using scanning tunneling microscope and break junction techniques. For conventional break junctions, the reported drift of the interelec trode spacing in the tunnel regime is typically of the order of 0.5 pm /min (1 pm=10(-12) m). We have nanofabricated break junctions which di splay a drift smaller than 0.2 pm/h. The improvement results from the scaling down by two orders of magnitude of the device dimensions. We d escribe the nanofabrication process, which can be adapted to most meta ls. We have performed measurements on Al, Cu, and Nb devices. The resu lts illustrate the ability of the technique to explore phenomenalike c onductance quantization and two level fluctuations. These new adjustab le atomic size contacts and tunnel junctions can be integrated in comp lex circuits. (C) 1996 American Institute of Physics.