The Electronic Properties Of Two-dimensional Nitride Materials

The excellent electronic properties of graphene have inspired researchers to explore other new two-dimensional?2D?materials.As a neighbor of carbon,the novel electronic properties and remarkable stability of 2D nitride materials composed of nitrogen element have aroused the interest of researchers and become a hot research topic in the field of 2D materials.Nitrogen is one of the elements with very high electronegativity,which can form a variety of nitride materials combined with various elements easily.In this thesis,we will propose several 2D nitride materials and study their electronic properties.There are five chapters in this thesis.The first chapter briefly describes the research status of 2D materials.At the same time,the unique electronic properties of Dirac point and flat band in 2D materials are introduced.In chapter two,we introduce the first-principle theory and the tight-binding model.In chapter three,we propose two new 2D boron nitride?BN?structures:5-7 BN and Kagome BN.These nitride materials show good stability and unusual electronic properties.It is worth mentioning that most 2D or 3D boron nitride structures are wide band gap insulators but the new structures are metallic materials,which is very rare.More interestingly,the calculations show that there are Dirac points on the Fermi level of 5-7 BN,indicating that 5-7 BN is a typical Dirac material.The velocities of Dirac electrons are approximate 10⁵ m/s.For Kagome BN,there are two flat bands below the Fermi level,and the flat bands generate heavy fermions in the structure.Furthermore,strong magnetism appears in the Kagome BN by one-hole doping,which results the flat band splits to spin-up and spin-down bands.In addition,the possible route to experimentally grow 5-7 BN and Kagome BN on suitable substrates such as Pb O₂?111?surface and Cd O?111?surface are also discussed.In chapter four,we find that the transition can be realized in 2D materials made of zigzag chains.The origin of the transition is that some orbital interactions in the zigzag chains will change drastically as the structure deforms,which change the dispersion of the corresponding energy bands.Furthermore,two stable nanomaterials,2D phosphorous nitride?PN?and arsenic nitride?As N?are proposed.PN and As N are intrinsic type-I and type-II Dirac semimetals,respectively.And they transit to another type of Dirac semimetals under compressive and tensile strains,respectively.Finally,we propose a possible route to grow PN on Si substrate,and hope some experiments can be carried out to validate and extend our findings.In chapter five,we summarize the previous studies and show the prospect about the studies in the future.