Interfacial Mechanical Properties Of Heterogeneous Two-dimensional Materials

Graphene is one of the most promising two-dimensional(2D)materials as its exceptional properties,and hexagonal boron nitride(h-BN)has a honeycomb structure similar to that of graphene.Layered heterostructures comprised of graphene and h-BN have a wide application potential in the fields such as functional devices and nanoelectromechanical systems(NEMS).In this thesis,by using continuum mechanics modelling and first-principles calculations based on density functional theory,the interfacial friction properties of graphene/h-BN heterostructures as well as the effects of surface functionality and the electromechanical coupling of few-layer graphene and h-BN wrinkles have been extensively studied.The main works and findings of this thesis are listed below:(1)Reduction of interfacial friction in commensurate graphene/h-BN heterostructures by surface functionalization:Our first-principles calculations show that surface fluorination and oxidation could remarkably reduce the interfacial friction in commensurate graphene/h-BN heterostructures,as the adsorbed F and O atoms significantly suppress the interlayer electrostatic and vdW energy corrugations.The established empirical registry index models further reveal the difference between the roles of the F and O atoms in affecting the sliding energy landscapes,which are also utilized to predict the interlayer superlubricity in a large-scale oxidized graphene/h-BN system.(2)Mechanical and electronic coupling in few-layer graphene and h-BN wrinkles:We study the mechanical and electronic coupling in few-layer graphene and h-BN wrinkles by combining the firstprinciples calculations and the classical continuum mechanics(CM)model.Our CM model can give a good description for the wrinkling of few-layer graphene and h-BN sheets and a way to estimate their bending stiffness.The change of wrinkle geometry and the enhancement of interlayer interactions with thickness increases significantly alter charge distributions at the few-layer wrinkles.In contrast to monolayer wrinkles,the electronic properties of few-layer wrinkles become more sensitive to bending deformation.