Research On Properties Of Surface And Interface Of Aluminum And Graphene By First Principle Method

Aluminum nitride(AlN),as a typical representative of the third-generation semiconductor material,has received wide attention.It plays an important role in optoelectronic devices,especially deep in the aspect of deep ultraviolet light emission devices and deep ultraviolet detectors.However,due to its wide band gap,the carrier concentration and mobility at room temperature are relatively low,which affects the electrical performance of aluminum nitride-based electronic devices.In recent years,two-dimensional materials have developed rapidly due to their excellent properties.These new materials could open a new way for improving the performance of aluminum nitride-based devices.Graphene has high carrier mobility at room temperature.If the carriers generated from aluminum nitride are introduced into graphene for transmission,it can effectively solve the problem of low carrier mobility in aluminum nitride-based devices.In addition,due to the lack of dangling bonds on the surface of the two-dimensional graphene material,the weak van der Waals force contact between aluminum nitride and graphene can overcome the effect of the lattice mismatch between the two materials,and thus it is expected to improve the overall performance of the device.At the same time,the combination of aluminum nitride and graphene can also be applied to flexible device.For devices,the surface and interface of the two substances is the key factor that determines the microscopic and macroscopic properties.Therefore,it is necessary to understand the interaction mechanism between aluminum nitride and graphene,and to further study the surface interface between the two.In this paper,first-principles calculations are employed to investigate the structural and electronic properties of heterostructures based on aluminum nitride and graphene.Initially,the three low-index planes of wurtzite AlN are studied,including two polar planes,that is(0001)and(000(?)),and non-polar planes(10(?)0).After full relaxation,the structural and electronic properties of three surfaces are compared.The calculated surface energy of aluminum nitride(0001),(000(?))and(10(?)0)plane is 7.85 J/m~2,8.24J/m~2 and 8.15 J/m~2,respectively.Among them,the surface energy of(0001)plane is the smallest.The surface states of the three planes only exist at a few atomic layers on the surface.The farther away from the surface,the less affected the aluminum nitride atomic layer is by these surface states.The interface structure and electronic properties of the three interfaces of AlN(0001)plane/graphene,AlN(000(?))plane/graphene and AlN(10(?)0)plane/graphene were then studied.The AlN(0001)plane/graphene interface has the largest binding energy and the smallest interface distance.Differential charge density and charge population show that charge rearrangement mainly occurred at the interface of the three systems.Local electron density analysis indicate that the interaction between graphene and aluminum nitride(10(?)0)surface is the most obvious.There are many new energy peaks in the total state density of aluminum nitride.And the shape of these peaks is similar to that of graphene.