Stable Ohmic contacts achieved in hydrogenated graphene/C3B van der Waals heterojunctions

Two-dimensional (2D) heterojunctions with stable Ohmic contacts are basis for developing novel nanoelectronics devices. Here, we construct graphene/C3B and various hydrogenated graphene(Hi)/C3B (i = 1, 3, 5, 7) van der Waals heterojunctions. Calculations show that they have high energetic, mechanic and thermodynamic stability, and the pristine graphene/C3B and graphene(H1)/C3B heterojunctions feature n-type Schottky contacts, while graphene(Hi)/C3B (i = 3, 5, 7) heterojunctions can realize n-type Ohmic contacts inherently, meaning that increasing hydrogenated concentrations is beneficial to achieve Ohmic contacts for heterojunctions. Particularly, to examine the stability of their electric contact property, various physical controlling effects are investigated. It is found that under all studied physical controls, the pristine graphene/C3B and graphene(H1)/C3B heterojunctions always exhibit Schottky contact behaviors. Interestingly, graphene(Hi)/C3B (i = 3, 5, 7) heterojunctions maintain Ohmic contacts unchanged under vertical strain, forward electric field, and tensile biaxial strain. Only at higher reversed electric fields (larger compressive biaxial strains), the graphene(H5)/C3B and graphene(H7)/C3B (graphene(H3)/C3B) are changed from n-type Ohmic contact to n-type Schottky contact, but with a very small Schottky barrier height (quasi-Ohmic contact). These findings demonstrate that the graphene/C3B heterojunctions with suitable hydrogenated concentration exhibit a very high stability to preserve Ohmic contact, providing the material basis for designing related devices.