Edge Modification And Surface Adsorption Of The Graphene-like Low-dimensional Materials:A First Principles Study

Low-dimensional nanomaterials possess many novel properties,different from traditional block materials,which make those materials have promising application prospect in electronics,optoelectronics,electrochemistry,gas sensors and related fields.With the continuous improvement of computer processing speed and development of computational theory,it has gradually become the mainstream that employs theoretical model and first-principles calculation method to provide a reasonable interpretation to experimental results or predict properties and performances of nanomaterials and the corresponding electronic component.In our dissertation,by using first-principles calculations method,we systematically study the effect of edge modification to zigzag BC₂N nanoribbons and the effect of surface adsorption and sensing performance to blue phosphorene.This dissertation contains five chapters:In chapter 1,we demonstrate research background and the latest research progress of low-dimensional nanomaterials.The structural characters,electronic structures,transport properties,experimental preparation methods,and potential applications of zigzag BC₂N nanoribbons and blue phosphorene have been described in detail.In chapter 2,we introduce the basic information of first-principles,density function theory?DFT?,nonequilibrium Green's function?NEGF?and the calculation software and package used in this dissertation.In chapter 3,we employ first-principle calculation to investigate the effect of edge modification with H,F,Cl,O,S,Se atoms and OH molecule on zigzag BC₂N nanoribbons.Different modification structures and nanoribbon widths have been considered,we focus on the the structural character,stability,electronic structure?band gap,direct gap and indirect gap?and magnetic property?ferromagnet,antiferromagnet and nonmagnet?.The calculation results show that edge condition and nanoribbon width have great influence on structure,electronic and magnetic properties.The edge modified nanoribbons show half-metalic and metalic properties depending on modificaton species.The O-terminated zigzag BC₂N nanoribbon possess a ferromagnetic ground state.The stability of all investigated nanoribbons imporve with increasing ribbon width.Besides,the band gaps of semiconducting nanoribbons decrease with increasing ribbon width.When the nanoribbon width is large enough,the band gaps of the pristine ribbon and OH,F-terminated zigzag BC₂N nanoribbons close,H-terminated nanoribbon show a half-metallic property.In chapter 4,On the basis of density function theory?DFT?and nonequilibrium Green's function?NEGF?calculation method,we investigate the adsorption behaviors of various gas molecules?CO,CO₂,NO,NO₂,NH₃,SO₂ and H₂S?on blue phosphorene.The most stable adsorption sites,stabilities,charge transfer,electronic structures,magnetic properties as well as transport performance are systematically discussed in this dissertation.All the investigated gas molecules are psysisorptions on blue phosphorene.Given that there is no significant deformation in the adsorbed systems,the blue phosphorene is still stable after gas molecule adsorptions.After adsorptions,blue phosphorene remains semiconducting properties The blue phosphorene show ferrosmagnetic ground states with the adsorptions of NO and NO₂ molecules,and the magnetic moments are both 1.0 ?B.The quantum transport calculations demonstrate the transport currents of blue phosphorene have different degrees of change,exhibiting great sensitivity,which suggest a new research direction for high-performance gas sensors.In last chapter,we summary our work,and prospect the future investigation on this topic.