First-principles Study Of Graphene/h-BN Heterobilayers With Point Defects

Two-dimensional nanostructures, which is the research hotspot in recent years,has attracted many attentions of the researchers. As the typical representative intwo-dimensional nanostructures, graphene, has special Dirac electronic properties, highelectron mobility, unique electron transport properties and has been investigatedextensively from the scientific community. Graphene-like material such as single-layerhexagonal boron nitride (h-BN) has successfully on the preparation of the experiment.h-BN has good chemical stability, excellent mechanical properties, high melting pointand etc. h-BN can form a stable stacking structure with graphene, high qualitygraphene were successfully grown on h-BN in a controllable manner. Usingfirst-principles calculations, we investigate systematically the impact of three differentpoint defects, including vacancy, substitution and combination of them. The structural,electronic and magnetic properties of graphene/h-BN heterobilayers have been studied.the main conclusions are as follows:Firstly, we investigate the optimized structures of vacancy point defects, includingB vacancy, C vacancy, N vacancy, B and C vacancy, N and C vacancy. B vacancyhetero-bilayer is found to be most stable energetically. N and C vacancy hetero-bilayermaintain the semiconductor property with a larger direct band gap in majority andminority spin bands, the others behave metal properties. All structures show magnetism.Magnetism behavior of the configuration that C vacancy is predominantly contributedfrom the only two C atoms around vacancy, which is different from other magnetismmoment which are contributed from the three C atoms around vacancy position. Thedistributions of electron spin density and the number of the spin-up and spin-downelectrons over all occupied states is consist with the Bader analysis.Secondly, we investigate the optimized structures of substituional point defects,including B or N in h-BN substituted by C, C in graphene substituted by B or N, C ingraphene exchanges the position with B or N in h-BN. C substitution by N inhetero-bilayer is found to be most stable energetically. The configurations in anti-sitesubstitution between C and B maintains the semiconductor property with a larger directband gap in majority and minority spin bands, the others behave metal. Bothhetero-bilayers of N in h-BN substituted by C and C in graphene substituted by N showmagnetism. Lastly, we investigate the optimized structures of combination of vacancy andsubstitution, including B vacancy and C in graphene substituted by B or N, C vacancyand B or N in h-BN substituted by C. The hetero-bilayer of B vacancy and C ingraphene substituted by N is found to be most stable energetically. The hetero-bilayerof B vacancy and C in graphene substituted by N also maintain the semiconductorproperty. Nevertheless, B vacancy and C in graphene substituted by B hetero-bilayerbehave half-metal, the others become metal. All structures show magnetism. As onenearest neighbor C atom around vacancy show minor contrary magnetic moment. Themagnetism behavior of the hetero-bilayer that B vacancy and C in graphene substitutedby N is predominantly contributed from the two C atoms around vacancy.