Synthesis And Growth Mechanism Exploration Of Two-dimensional Antimonene And Bismuthene

Two-dimensional materials have attracted intense interest in the field of material science,physics as well as chemistry in the recent years due to their unique mechanical,electronical and catalytic properties.Some of the predicted properties of two-dimensional group-VA elemental materials have so far been validated by experiments.The synthesis of two-dimensional group-VA elemental materials such as antimonene or bismuthene,however,is still key to the exploration of two-dimensional group-VA elemental materials.In this work we shall report the growth of two-dimensional antimonene and biamuthene via molecular beam epitaxy.By controlling the deposition rate and substrate temperature we fulfilled the growth of two-dimensional antimonene and bismuthene and control over the morphology.Atomic force microscope,scanning electron microscope and Raman spectrum were used to investigate the morphology and crystallinity of as-grown samples.In addition,theoretical calculations were employed to investigate the process and mechanism of growth.As follow is the main work in this article:1.Molecular beam epitaxy growth of two-dimensional antimonene and the exploration of growth mechanism.Successful fabrication of fractal-shaped few-layer antimonene on HOPG via Molecular beam epitaxy was achieved for the first time.During the process of growth,the deposition rate and substrate temperature was found to determine the morphology of antimonene and control over the deposition rate and susbtrate temperature was exercised to achieve samples with certain morphology.SEM and AFM profile showed fractal structure of the sample and the lateral size of flakes ranging from 2?m to 14 ?m.The AFM image showed that the thickness of the sample can reach as thin as 3.5 nm with obvious terraces on the surface.Raman spectroscopy was used to explore the structure of the synthesized sample.As the thickness decrease,the Raman peak shifts to higher wavenumber,namely blueshift.To explain the formation of the fractal structure,diffusion limited aggregation theory and phase-field equation were further used to simulate the process of growth.The parameter K,which represents for the latent heat during growth was found to be related to the growth pattern.This work provided experimental evidence of successful fabrication of fractal-shaped few-layer antimonene on HOPG and theoretical calculation to simulate and explain the formation of the unique shape.2.Synthesis of bismuthene on HOPG and exploration of relationship between symmetry of materials and growth pattern.In this work the growth of two-dimensional Bi(110)nanoribbons on HOPG was realized via molecular beam epitaxy.Atomic force microscope characterizations showed that the thickness of a single nanoribbon was around 2.8 nm.Terrace with a thickness of 0.4 nm could be achieved on the surface of some nanoribbons.Furthermore,the scanning electronic microscope images showed that certain amount of ribbons were perpendicular to each other.To explain this phenomenon,phase field equation and DFT calculation was employed to investigate the growth mechanism of Bi(110)on HOPG.Through DFT calculation,it was found that the distance between Bi atom and HOPG was larger than that in bulk Bi crystal and the binding energy between Bi and HOPG was-0.041 eV,which revealed the Van der Waals interaction between bismuthene and HOPG substrate.When the mode of anisotropy,corresponding to the symmetry of atomic structure of bismuthene,was chosen to be 4,the simulated pattern of phase-field models with bismuthene nanoribbons perpendicular to each other was achieved,which showed that the symmetry of Bi(110)atomic plane contributed to the symmetry of growth pattern of bismuthene on HOPG.In the end,we summarized our work and made further research plan about it.Dut to terrace on the surface of antimonene and conductivity of HOPG substrate,STM or ARPES measurement could be conducted to explore the topological properties as well as band structure of antimonene.The relationship between symmetry of atomic structure and morphology of grown samples reavelled by the research of bismuthene could boost synthesis of other two-dimensional materials.