Universal conductance fluctuations in metallic nano-structures

WE investigated the magneto-conductance of gold nano-wires in a in mesoscopic 2-probe configuration. The nano-structures were fabricated using a four-layer resist system and Electron beam lithography. The samples consisted of a wire of length L=100-1000 nm and cross section 30 x 30 nm(2) connected to two funnel-shaped contacts, At very low temperatures T similar or equal to 100mmK the magneto-conductance of all measured devices showed a rms-value delta G approximate to 0.1e(2)/h. Our measurements demonstrate that the conductance fluctuations are strongly influenced by the contacts. This is most significant in the correlation field B-c similar to 1/F psi which decreases with decreasing wire length. We also observed a weak dependence of delta G on the wire length L which can be interpreted as a dimensional crossover from 1D (L greater than or equal to 400 nm) to 2D (L less than or equal to 200 nm).