Theoretical And Experimental Research On Layered Hexagonal Boron Phosphide

The discovery of graphene has promoted the research boom of a series of two-dimensional semiconductor materials including molybdenum disulfide,tungsten disulfide,manganese dioxide,phosphene.Two-dimensional semiconductor materials have excellent optical,mechanical,electrical and magnetic properties,and have important application prospects in the fields of energy,environment,and biomedicine.At the same time,there are certain defects in the two-dimensional semiconductor material.For example,the electron mobility of the transition metal sulfide is generally low,and the phosphene is self-degraded in the moist air.Therefore,the preparation of two-dimensional semiconductor materials with excellent performance and high stability is still in the development and exploration stage.The search for two-dimensional semiconductor materials with high carrier mobility and excellent photoelectric response is one of the hot topics in the field of condensed matter physics.In this paper,we have studied the theoretical and experimental preparation of a new type of two-dimensional semiconductor material,hexagonal boron phosphide(2H-BP),which mainly includes the following two parts:1.Based on the first-principles-based software VASP calculation,the optimized 2H-BP electronic structure is a graphene-like honeycomb structure.2H-BP is an intrinsic direct band gap semiconductor,and the band gap can be adjusted between 0.3-1.43 eV by layer dependence.The electron carrier mobility is as high as 106 cm2 V-1 s-1.By simulating the phonon spectrum and phonon density of monolayer 2H-BP,it is shown that the phonon spectrum has no imaginary frequency and it is determined that the monolayer 2H-BP is dynamically stable.By comparing the interatomic bonding energies of graphene,phosphene and silicene,the stability of 2H-BP is better than that of phosphene and silicene.The 2H-BP stress adjustment calculation results show that the electronic structure of uniaxial strain does not change significantly within 10%,indicating that 2H-BP has good chemical stability.When the uniaxial strain reaches 10%and the biaxial strain reaches 15%,the monolayer 2H-BP transitions from a direct band gap to an indirect band gap semiconductor.2.Synthesis of 2H-BP Microcrystals.Using chemical vapor deposition(CVD)with SiO2/Si as the substrate,black phosphorus and high-purity boron powders as precursors,in high-purity argon(Ar)atmosphere,we synthesis of 2H-BP microcrystalline samples in different size ranges at different temperatures of 800-950?.Through scanning electron microscopy(SEM),transmission electron microscopy(TEM),selected area electron diffraction(SAED),it showed that the synthesized sample had a hexagonal lamellar structure.And powder X-ray diffraction(XRD)showed that the synthesized sample grew mainly along the(002)crystal plane.For our synthesized 2H-BP microcrystals,it can be further stripped into a few layers or a monolayer 2H-BP to prepare field effect transistors or other optoelectronic devices,which will become a new research direction for two-dimensional semiconductor materials.