Overview of electron emission laws from 2d materials

In this paper, we present an overview of the novel scaling laws of thermionic emission (TE), field emission (FE) and photoemission (PE) for two-dimensional (2D) materials. For these emerging materials, we express the emission models in the form of ln(J/K-beta) proportional to 1/K, where J is the emission current density, K is temperature (T) for TE and K is dc or optically field for FE and PE. Here, the scaling is beta=3/2 and beta=1 for electron emission in lateral (or edge) and vertical (or surface) direction, respectively, which is different from the traditional scaling of beta = 2 for bulk 3D materials.