Coulomb Blockade and Digital Single-Electron Devices

Tunneling of single electrons has been thoroughly studied both theoretically and experimentally during last ten years. By the present time the basic physics is well understood, and creation of useful single-electron devices becomes the important issue. Single-electron tunneling seems to be the most promising candidate to be used in the future integrated digital circuits with the typical size scale of few nanometers and below, i.e. in the molecular electronics. In the review we first briefly discuss the physics of single-electron tunneling and the operation of the single-electron transistor. After that, we concentrate on the hypothetical ultradense digital single-electron circuits and discuss the different proposed families of them. The last part of the review considers the issues of the discrete energy spectrum and the finite tunnel barrier height which are important for the molecular-size single-electron devices.