Structures And Properties Of Novel Borophenes And Li Decorated α-borophene: A Theoretical Study

Owing to their unique geometries and electronic properties, two-dimensional(2D) boron nano-materials hold great potential for a wide range of applications in environmental protection, energy, electronics and so forth. In this study, three issues are investigated by first-principles density functional theory calculations.In the first aspect, we constructed two novel boron sheets, i.e., α6- and β14-sheets, with five isomeric configurations for each sheet, using the experimentally available B36 and B35 building blocks. The thermodynamically stabilities of α6- and β14-sheets were analysed by the optimized structures and binding energies. Additionally, by use of the computed frontier molecular orbitals, electronic density differences, and densities of states, the bonding nature of the novel α6- and β14-sheets was elucidated qualitatively. Moreover, we theoretically computed the work functions of the two novel sheets, which were further analyzed and compared with the commonly used and promising materials, such as Mg and graphene.In the second study, we focused on the Li-decorated boron α-sheet(Lin/BBST) system. We computed the binding energies, electronic properties, and work functions for all optimized configurations and selected forteen configurations based on their binding energies, which were further investigated on their thermodynamic stabilities and stabilization mechanism based on the computed energies. Furthermore, we explored the dependence of work function on Li concentration and decoration configuration, which was further identified by the electrostatic potential analysis. Additionally, the dependence of the work function of Lin/BBST systems on the shifts of the Fermi and vacuum energy levels was explored, which can be further used to elucidate the intrinsic physical mechanism for adjusting work function.In the third study, we investigated the field emission properties for the four singleside-decorated Lin/BBST systems. The geometry dependence on electric field was discussed based on the optimized geometries of Lin/BBST under given electric fields. In the optimizations, the binding energies, charges, energy levels, and DOSs of Lin/BBST were obtained. The thermodynamically stabilities of the selected four single-sidedecorated Lin/BBST systems were evaluated using the calculated binding energies. Also, we investigated the effect of electric field on the binding energy. Finally, the field emission properties of BBST and the single-side-decorated Lin/BBST were forecasted based on the calculated work functions and ionization potentials under given electric fields, and the mechanism of field emission reinforcement was revealed using the computed electronic properties.Firstly, the relevant theoretical researches offer new structures for 2D boron sheets family and provide new systems for future investigations of 2D and one-dimensional(1D) nano-materials. Secondly, the results would provide some useful insights into the design of 2D and 1D nano-materials with tunable work function. Meanwhile, our study is beneficial to provide a theoretical reference for the application of 2D boron nanomaterials in field emission devices.