Electronic Structure And Field Effect Of SiC Nanoribbons : A First Principles Research

Material is the sign of human civilization and progress, it is the basis of the progress of science and technology, so nanometer material is inevitable choice of the world’s major decision. With the important progress of the condensed matter physics and nanometer materials, semiconductor microstructure, high temperature superconducting materials, new thermoelectric materials, photonic crystals and other new materials are emerging. Besides, silicon carbon nanomaterials are belong to the current research hot spot, facing great opportunities and challenges. Due to its excellent thermal physical properties, it is used for the application of high temperature and high power equipment. Since it has broad band gap, study of the large SiC structures in the optical and electronic structure is a hot area.In this paper, we using the first principles calculation method based on density functional theory of CASTEP software packages, and buid up super cell model, based on the mode of conservation constraint potential system, study of the electric field effects of the zigzag SiC nanoribbons(ZSiCNR), and the dispersion curve and the phonon spectrum. Specific work are as follows:First, use first principles plane wave pseudopotential method for silicon carbon nanoribbons and geometry structure optimization and electronic structure calculations. Study three kind of narrow zigzag Si C nanoribbons, 2ZSiCNR, 3ZSiCNR, 4ZSi CNR respectively. When calculating the electronic structure, we choose different electric field intensity, calculating the spin polarization, band structure and density of states. Concrete zigzag silicon carbon nanoribbon was studied, focusing on the effect of edge of the nanoscale structure on bandgap, especially near the Fermi surface conduction band and valence band are calculated by three different width of nanoribbon. Near the Fermi surface, spin of the electron distribution in the cell is also sutdied. Results show that the width of gap changes. Near Fermi level the influence of electrid field on distribution of different electron spin is different, and for 2ZSiCNR width of band gap decreases with increasing applied electric field. For 3ZSi CNR and 4ZSiCNR near the Fermi the spin degeneracy is removed, band gap increases, reverse electric field shows ZSiCNR owns an internal self-built electric field.Second, we use density functional perturbation theory(DFPT) to calculate the ZSiCNR and the phonon dispersion curves. According to the dispersion curves and characteristic frequency, it can be judged the stability of the ZSi CNR structure.Finally, summary of the research work of this paper. Silicon carbide nanoribbons, internal self-built electric field will offset or enhance the effect of external electric field, the one-dimensional silicon carbide nanoribbons has internal electric field which interact with external applied field and the band gap changes along with the electric field effect. These unique properties of silicon carbide nanoribbons can be used in the device design of super capacitor.