Operation of Metal Single-Electron Devices is based upon the Russian orthodox theory  of Coulomb Blockade (K. Likharev,  D. Averin). All these devices are using small metallic (Al, Au) islands as "dots" separated from the external world by 0.5-2 nm thick,  layers of oxide (primarily Al₂O₃) with lateral dimensions of about 50x50 nm². The greatest advantages of these devices are relative simplicity of design fabrication and good uniformity of the devices in one batch which allows to build rather complicated circuits. The major drawback of this technology is relatively small charging energy (typically on the order of 1 meV) due to relatively large capacitance of the junctions (~100 aF). Here is an example of one of the first Single-Electron Transistors (SET) fabricated at Notre Dame ( by Islamshah Amlani, 1996).