The Layer-Dependence on the Work Function and Degradation Evolution of Black Phosphorus*

Black phosphorus (BP) has been received great attention due to the layer-electronic structure. This layer-dependent electronic structure of BP shows not only the variation of bandgap but also work function (WF) shift. These layer-dependent electronic properties at such interfaces are key parameters to determine interfacial properties, such as Schottky barrier and charge redistribution. Furthermore, the fast degradation of BP is currently a critical obstacle for an application. Since the degradation progress at the interface between BP and O₂/H₂O molecules in ambient condition, the layer-dependent electronic properties are key parameters to understood the degradation process of BP.
In this regards, we focused on the layer-dependent WF and its evolution of BP by scanning Kelvin probe microscope measurement in ambient condition. It shows that the WF of the bilayers increases by 0.12 eV than that of bulk. The layer-dependent work function of BP was discussed in detail by our first-principles calculations. In addition, the layer-dependent degradation behaviors were observed. These behaviors were understood by the oxidation kinetic model based on the Marcus-Gerischer theory.