Effect of the electromagnetic environment on Coulomb blockade devices: Model, experiments, and method of analysis

The effect of the electromagnetic environment on Coulomb blockade devices can be estimated through a simple horizon model where the interaction length is determined by the Heisenberg uncertainty principle. The advantage of this horizon model can be demonstrated in a device with two tunnel junctions in parallel where a cutoff voltage related to physical dimensions is observed. This model also explains the characteristics of single junctions and single-electron tunneling (SET) transistors. Several Al/AlOₓ/Al devices of various geometries were measured and the effective Coulomb barrier has been investigated through the offset voltage defined as Voff≡V-IdV/dI. We have also used Voff to determine the capacitances of SET transistors, from which we determined microstrip capacitance as a function of island size.