The Electronic And Magnetic Properties Of Chemically Decorated Boron Nitride Sheet: First-principles Study

Graphene has attracted worldwide attention due to their special electronic properties and geometric structure since Geim et al found stable single-layer structure in 2004. Scientists show great interest on graphene and graphene derivatives (graphane, graphone and graphene nanoribbons) both experimental and theoretical studies. Theoretical calculation predicted that graphene has potential applications in nanoelectronics. The atomic structure of boron nitride (BN) sheets is similar to the honeycomb structure of graphene, except that the constituent atoms of the former are from III and V columns of the Periodic Table. Hence, the upsurge of study BN sheets followed. Analogy to the study of graphene and graphene nanoribbons, based on BN sheets as a basic configuration, we calculated the electronic and magnetic properties of partially decorated BN sheets with H, F, and OH decoration using density functional theory (DFT).In this thesis, we firstly introduce the research background, and then give a general discussion on the basic principles as well as the latest development in the first-principles methods. Finally, we calculate structural stability, electronic and magnetic properties of chemically decorated pure BN sheets using the first-principles plane-wave calculations within density functional theory. Through the fully geometry optimization and energy calculation, the electronic properties of chemical decoration of BN sheets different from pure BN sheets'. In the case of BN sheets decorated by F and OH with zigzag types, the systems are half-metallic where majority-spin state remains as indirect band-gap insulator with band gap of 5.19 eV and 5.05 eV, respectively, while minority-spin state is metallic. But for armchair types, the systems are still semiconducting. Note that the band gap of the minority-spin states is very small and close to zero, comparing to the large band gap (5.668 eV for F,5.228 eV for OH) of majority-spin state. Also, the BN sheets decorated by H with zigzag types exhibit semiconducting behavior with large band gap (4.283 eV) of majority-spin and narrowed band gap of minority-spin that the lowest-energy conduction band near the Fermi level. Systems decorated by H with armchair types are metallic with energy gap is zero. Specifically, all the systems become magnetic and the total magnetic moments of all systems are close to or equal to 2μB.