FORMATION AND MANIPULATION OF A METALLIC WIRE OF SINGLE GOLD ATOMS

The continuing miniaturization of microelectronics raises the prospect of nanometre-scale devices with mechanical and electrical properties that are qualitatively different from those at larger dimensions. The investigation of these properties, and particularly the increasing inf luence of quantum effects on electron transport, has therefore attract ed much interest. Quantum properties of the conductance can be observe d when 'breaking' a metallic contact: as two metal electrodes in conta ct with each other are slowly retracted, the contact area undergoes st ructural rearrangements until it consists in its final stages of only a few bridging atoms(1-3). Just before the abrupt transition to tunnel ling occurs, the electrical conductance through a monovalent metal con tact is always dose to a value of 2e(2)/h (approximate to 12.9 k Omega (-1)), where e is the charge on an electron and h is Planck's constant (4-6). This value corresponds to one quantum unit of conductance, thus indicating that the 'neck' of the contact consists of a single atom(7 ). In contrast to previous observations of only single-atom necks, her e we describe the breaking of atomic-scale gold contacts, which leads to the formation of gold chains one atom thick and at least four atoms long. Once we start to pull out a chain, the conductance never exceed s 2e(2)/h, confirming that it acts as a one-dimensional quantized nano wire. Given their high stability and the ability to support ballistic electron transport, these structures seem well suited for the investig ation of atomic-scale electronics.