Transport in gold cluster structures defined by electron-beam lithography

The near-room temperature current-voltage ($\mathrm{I-V}$ ) characteristics of small structures made from the metal-cluster material ${\mathrm{Au}}_{55}{\mathrm{[P(C}}_{\mathrm{6}}{\mathrm{H}}_5{)}_3{]}_{12}{\mathrm{Cl}}_6$ were studied. It is shown that these electron-beam defined structures have highly nonlinear characteristics with features, including a threshold voltage and scaling behavior, which are consistent with Coulomb charging of individual ${\mathrm{Au}}_{55}$ cores in a disordered array. Applied radio frequency signals introduce plateaus in the $\mathrm{I-V}$ characteristics, which demonstrates the presence of coherent tunneling in these cluster systems.