Intrinsic correlation between electronic structure and degradation: from few layers to bulk black phosphorus.

Black phosphorus (BP) has received much attention owing to its fascinating properties, such as a high carrier mobility and tunable band gap. However, these advantages have been overshadowed by the fast degradation of BP under ambient conditions. To overcome this obstacle, the exact degradation mechanisms need to be unveiled. Herein, we analyzed two sequential degradation processes and the layer-dependent degradation rates of BP in the dark by scanning Kelvin probe microscopy (SKPM) measurements and theoretical modeling. The layer-dependent degradation was successfully interpreted by considering the oxidation model based on the Marcus-Gerischer theory (MGT). In the dark, the electron transfer rate from BP to oxygen molecules depends on the number of layers as these systems have different carrier concentrations. This work not only provides a deeper understanding of the degradation mechanism itself but also suggest new strategies for the design of stable BP-based electronics.