Conductance fluctuations in metal-nanoparticle-metal junctions

Abstract

We have fabricated devices where the gap between a pair of gold electrodes was bridged by a 20 nm gold particle stabilized with a citrate coating. The current-voltage characteristic I _˜ (V-V_t)^ξ (with voltage threshold V_t ≈ 0 and scaling exponent ξ=0.93) is attributed to charge transport in a one-dimensional path. Current fluctuations at a fixed bias voltage were observed, with a fluctuation amplitude I_s proportional to the voltage applied voltage. A Fourier analysis of I_s(t) showed that the higher harmonics s_n of these conductance fluctuations follow a power law s_{n ˜} f^μ (with μ = -0.62 in the range 3-30 mHz and μ = -1.08 in the range 30-100 mHz). We demonstrate that current fluctuations derive from conformational changes in the citrate molecules induced by a charge transfer across the molecules.