Modeling of electron emission from graphene and metal tip

In this paper, we report our models on electron emission frm graphene and metallic tips. For graphene, we will cover 3 types of emission: field emission, over-barrier photo-emission and thermionic emission. On each model, we will highlight the main difference as compared to the traditional models that were constructed for metallic materials. For metallic tip, we will report a time-dependent quantum tunneling and non-equilibrium model to study the transition from multiphoton emission to optical field emission when a dc-biased metallic tip is excited by an ultrafast laser pulse. In particular, we will highlight that the smooth transition and number of photons required will be less when the laser pulse duration is decreased to a few cycle regime.