Abstract
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})\propto 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.