OBSERVATION OF SINGLE-ELECTRON CHARGING EFFECT IN NBN SUBMICRON BRIDGES

Submicron NbN bridges whose thickness, width and length are 10nm, 100n m and 100-300nm respectively, ave been fabricated, and their conductio n properties and electrical field effect are measured. The samples hav ing resistances larger than approximately 100kOMEGA exhibit nonlinear I-V characteristics with offset voltage of 2mV approximately 12mV at 4 .2K which are obviously similar to those of the single-electron chargi ng effect in small tunnel junction arrays. The field effect modulation of the junction conductance is observed by applying a voltage to a ga te electrode which is made over the NbN bridge. These charging effects are thought to arise from the granular structure of NbN bridges. The simulation result using one-dimensional SET junction arrays coincide w ell with experimental result.