The Study On Tribological Properties And Electronic Properties Of Hexagonal Boron Nitride Induced By Normal Pressure

hexagonal boron nitride(h-BN)has attracted much attention from researchers because of its excellent chemical stability,heat resistance,oxidation resistance,especially good lubricity and significant electronic properties.In this thesis,we study the frictional properties and electronic properties of h-BN by using the first principles based on density functional theory.The results on investigation of friction properties show that the friction coefficient presents a trend of decrease firstly and then increase with the increase of normal pressure.This is related to the electron transfer between the upper and lower layers of h-BN at different sliding positions.The trend is similar to that of graphene,which shows that the difference in the electronic properties between h-BN and graphene does not affect its basic friction regular.Meanwhile,we find that the band gap of bilayer h-BN can be effectively tuned by normal pressure.And it surprisingly undergoes both decreasing and increasing trend with increasing of normal pressure under the stackings I and II which is considerably different from monotonously decreasing by applied electric field.While it undergoes monotonously decreasing under the stacking III.Furthermore,it is found that the transformation from a direct band gap to an indirect band gap can be achieved in the case of stacking pattern II as the compression above 34.3%.However,the insulator-semiconductor transition can be induced for stacking pattern I and III under the normal compression above 28.6%and 45.7%,respectively.These are beneficial for their potential applications as optoelectronic device and other nanoelectronic device materials.The further analysis of the above two parts shows that the variations of the tribological and electrical properties of hexagonal boron nitride under pressure are all caused by the electrostatic interaction between bilayer hexagonal boron nitride.These conclusions provide a theoretical basis for understanding the excellent tribological properties of hexagonal boron nitride at the macroscopic scale from the atomic scale and broadening its application in nanometer devices.