A Density Functional Theory Study Of The Electronic Structure And Magnetism In VS₂ Nanoribbons

Two-dimensional material greatly satisfies the future development of the integrated electronic system of portable ultra-thin, high transparency, good flexibility requirements, etc. For the last 10 years, despite graphene that has attracted much interest as a representative of two dimensional materials, recently attention has been paid to layered transition metal dichalcoginides (TMDCs) due to their superior properties such as mechanical, electrical and optical properties. However, most of the two-dimensional TMDCs materials do not have intrinsic magnetic. As a promising new layered inorganic material, vanadium disulfide (VS2) exhibit super ferromagnetic properties that can be used in spintronic devices. Based on density-functional theory, we systematically investigate two-dimensional VS2 monolayer and nanoribbons, and study its electronic magnetic properties by analyzing its electronic structures and magnetic moment. The main conclusions are summarized below:1) We explored the stability and the electronic properties of two-dimensional VS2 monolayer in honeycomb triclinic crystal (H-VS2) and the center of the honeycomb octahedral crystal system (T-VS2) phases and the effects of width on electronic properties of zigzag and edge VS2 nanoribbons. Although two-dimensional VS2 monolayer show the ferromagnetic semimetal and metal electronic properties in ground state, their total energy varies with the lattice constant (volume) of a parabolic variation contraction or expansion. Two configurations H and T can coexistent in the monolayer VS2 structure in certain strain condition. H-VS2 nanoribbons display larger magnetic moments than that of T-VS2 nanoribbons. Moreover, both 1D armchair and zigzag T-VS2 nanoribbons retain the metallic character of its bulk and 2D monolayer. However, the electronic properties of H-VS2 nanoribbons rely on the cutting ways and differ from that of 2D monolayer:the zigzag nanoribbons are metallic independent of the width, while the armchair nanoribbons display both metal, half-metal and semiconductor electronic behavior dependent of the ribbon width.2) We studied the vanadium sulfide nanoscale magnetic properties, the change rule of nanobelts, width and defects on the influence of the nanometer magnetic. The relation of the increase of magnetic moments and the ribbon width is remarkably different between the H phase and T phase, which is depend on the detail of geometry structures of nanoribbons. The total magnetic moments of H-VS2 NRs increase monotonically with the width change, while for T-VS2 NRs magnetic moments have a cyclical swing. In addition, we through exploring the optimized nanobelts, the internal space of relationship between key to analyze magnetic moment could be explained. Experimentally, deficiencies inevitably exist in material. We investigated the presence of sulfide deficiency of nanobelts influence on magnetic properties. We found that magnetic moments of VS2 may increase or decrease, yet may change from ferromagnetic to antiferromagnetic. And different position of sulfur deficiency of nanoscale magnetic effect is not the same.In conclusion, we mainly studied the stability of two-dimensional VS2 monolayer, and the effects of width and sulfide defect on electronic and magnetic properties of VS2 nanoribbons, which may be useful in developing new generation electronic and spintronic devices in future.