Abstract
This paper presents a modified Thomas–Fermi-approximated quantum model for space–charge-limited field emission in a nanogap with metal electrodes, where the image-charge potential (including anode screening), direct tunnelling, space–charge effects and exchange–correlation effects of the tunnelling current are treated in a one-dimensional quantum model. It is found that the traditional Fowler–Nordheim (FN) law (even with the classical model of anode screening) is no longer valid in a nanogap of less than 10 nm. The smooth transition of our proposed model to the traditional FN law extended to large gap spacing is demonstrated. Application of the model to estimate the emission area of an experimental I–V curve in a nanogap is discussed.