Gating the Conductivity of Arrays of Metallic Quantum Dots

Abstract

Experimental and computational studies demonstrating that the conduction of compressed, two-dimensional arrays of hexagonally ordered Ag quantum dots (QDs) may be varied through the influence of applied electric fields are reported and discussed. Monolayers of Ag QDs are incorporated into three-terminal (gated) devices, in which temperature, source-drain voltage (V_(sd)), gating voltage (V_g), compression of the array, and QD size distribution may all be varied. Experimental and computational results are compared in an effort to construct a physical picture of the system. Current vs V_(sd) plots at low temperatures exhibit systematic nonlinearities that change over to an ohmic-like behavior at higher temperatures and/or higher V_(sd). The voltage-induced transition is discussed as a transition of the conducting states from domain localized to delocalized. Such a transition was previously observed in the temperature dependence of the resistance. The computational model reveals that this transition is also highly sensitive to both the compression of the array and the size-distribution of the dots. We calculate the influence of V_g on the conductivity of the QD array, using the same computational model. In both the experiment and the model, we find a significant voltage gating effect and we observe hole-type conductivity of the array. Overall, the results demonstrate that low-temperature transport measurements provide a spectroscopic-like probe of the electronic states of the QD lattice. The theoretical approach further suggests that quite different gating behavior can be observed for electrodes with a different Fermi energy than the gold electrodes used in the experiment.