Black Phosphorus Field-effect Transistors

Black phosphorus is a layered allotropy of phosphorus that closely resembles graphite. But unlike graphene monolayer, black phosphorus is a semiconductor with a predicted band gap of $\sim$2 eV, which reduces to $\sim$0.3 eV in the bulk crystal. We investigate the electric property of black phosphors thin flakes with thickness down to a few nanometers. High conductance modulations up to 10$^{6}$ and field effect mobility up to 1000 cm$^{2}$/Vs at room temperature are achieved in a Metal-Insulator-Silicon (MIS) field effect transistor structure. We further uncover the mechanism that limits the mobility in black phosphorus thin flakes through temperature-dependent electronic transport measurements. Our results provide the first basic understanding of the electronic properties of black phosphorus thin flakes, and will greatly facilitate further exploration of its future applications.