Single Electron Transistor Fabrication using Focused Ion Beam direct write technique

We report on the fabrication of single electron transistors using focused ion beam (FIB) etching technology. Single electron transistors (SETs) are comprised of small conducting islands called the Coulomb blockade islands and tunnel junctions, allowing quantum mechanical tunneling of electrons onto and off of the islands. The typical random deposition of islands makes it difficult to fabricate SETs with the same parameters, because the position of the island strongly impacts the tunnel capacitance and resistance. We report the use of maskless FIB direct write technology to fabricate SETs, producing quantum islands less than 50nm in diameter. The FIB direct writing technique allows the exact placement of islands at a desired location in order to better control the device parameters. The initial characteristics of the devices, at room temperature, show that the Coulomb oscillations are smeared out, as expected for this condition. The conductance displays an asymptotic behavior, which is attributed to the operation of the SET in the strong tunnel regime and to its operation at room temperature