Single-electron Tunneling

The charge stored on a capacitor is not quantized: it consists of polarization charges generated by displacing the electron gas with respect to the positive lattice ions and can take arbitrary magnitudes. The charge transfer across a tunnel junction, however, is quantized in units of the electron charge (singleelectron tunneling), and may be suppressed due to the Coulomb interaction (Coulomb blockade). These simple facts lay the foundation for a new type of electronic device called single-electron tunneling (SET) devices. Coulomb blockade was first suggested back in 1951 by Gorter [123], who explained earlier experiments [164]. It remained largely unnoticed until, almost 40 years later, Fulton and Dolan built a transistor based on single-electron tunneling [109]. After introducing the concept of Coulomb blockade in Section 9.1, we will discuss basic single-electron circuits, in particular the double barrier and the single-electron transistor, in Section 9.2. Some examples and applications are given in Section 9.3.