Comment on “Design and circuit simulation of nanoscale vacuum channel transistors” by J. Xu, Y. Qin, Y. Shi, Y. Yang and X. Zhang, Nanoscale Adv., 2020, 2, 3582

These comments aim to correct some apparent weaknesses in the theory of field electron emission given in a recent paper about nanoscale vacuum channel transistors, and to improve the presentation of this theory. In particular, it is argued that a “simplified” formula stated in the paper should not be used, because this formula is known to under-predict emission current densities by a large factor (typically around 300 for an emitting surface with local work function 4.5 eV). Thus, the “simplified” formula may significantly under-predict the practical performance of a nanoscale vacuum channel transistor.