Coulomb blockade in a granular material made of gold nanowires

Uniform, 2 nm diameter gold nanowires were synthesized through the reduction of gold(III) chloride in an oleylamine matrix. They were top-contacted on a Si/SiO₂ substrate with metallic electrodes to manufacture back-gated transistors. Due to thermal breakage, the gold nanowires were fragmented into a granular material and the non-linear current-bias voltage characteristics measured on the devices from 7 K up to 300 K were described by the Coulomb blockade theory in a nearly one-dimensional quantum dot array. The electronic transport was governed by sequential tunneling at an applied bias above the global Coulomb blockade threshold, whereas in the Coulomb blockade regime, inelastic cotunneling was dominant up to 70 K, at which point it crossed over to activated behavior. The current dependence on the gate voltage that showed irregular oscillations was explained by the superimposition of Coulomb oscillation patterns generated by each different dot in the one-dimensional array. The competitive effects of excitation energy and stochastic Coulomb blockade balanced the number of current peaks observed.