Physical mechanisms leading to the coulomb blockade and coulomb staircase structures in strongly coupled multi-island single-electron devices

Controlled transport of electrons through tunnel junctions and their confinement by mesoscopic structures have opened up immense possibilities of single-electron device (SED) applications. The realization of a practical working SED has remained challenging largely owing to the poor understanding of the physics of operation of singe-electron tunneling devices, especially of those with multiple nanometer-sized islands. In this simulation study of one-dimensional (1D) multi-island chains, we propose physical mechanisms that lead to the coulomb blockade (CB) and coulomb staircase (CS) characteristics that are enhanced by the geometrical disorder in the chain. With increasing source-drain (VDS = VD − VS) bias, a multi-island device has to overcome multiple discrete energy barriers (up-steps) for charge advancement before reaching the threshold voltage (Vth). Beyond Vth, current flow is rate-limited by certain junctions with low transition rates, which leads to the CS structures in the current-voltage (IV) characteristic. Each step in the CS is characterized by a unique distribution of charges on the islands, each with an associated distribution of tunneling probabilities that depend on both the charge state and VDS. This study marks an important step in unraveling the microscopic details of SED operation and will inspire further experimental and theoretical studies