▎ 摘　　要

By considering the effect of Klein tunneling for low energy electrons with linear energy dispersion, a model has been constructed to calculate the amount of emitted line current density from a single-layer graphene sheet, which is vertically aligned inside a dc gap. It is found that the current-voltage scaling obtained from the constructed Klein tunneling model is very different from the traditional field emission model based on the Fowler-Nordheim (FN) law. Under the same geometrical field enhancement factor, our model predicts a much higher emitted current as compared to the FN law at low voltages. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3609781]