Thermal fluctuation-induced tunneling conduction through metal nanowire contacts

The temperature behavior of how electrons propagate through an insulating electronic contact formed at the interface between a submicron Cr/Au electrode and a metallic RuO(2) nanowire (NW) has been studied between 300 and 1 K. The NWs are typically of ∼70 nm in diameter and a few microns long. The submicron electrodes were fabricated by the standard electron-beam lithography technique. By employing the two-probe method, the electronic contact resistances, R(c)(T), have been determined. We found that, in general, R(c) increases rapidly with decreasing temperature but eventually saturates at liquid-helium temperatures. Such a temperature behavior can be well described by a thermal fluctuation-induced tunneling (FIT) conduction process which considers the crossover feature from thermal activation conduction at high temperatures to simple elastic tunneling conduction at low temperatures. The wide applicability of this FIT model has further been established by employing metallic IrO(2) and Sn-doped In(2)O(3-x) NWs. This work demonstrates that the underlying physics for the charge transport properties of an insulating electronic contact can be well understood.