First-principles Study Of Two-dimensional Nanoribbons And Van Der Waals Heterostructures

The innovative discovery of nanomaterials or nanostructures has promoted the development of materials science and nano-scale electronic devices.The discovery of graphene has also motivated scholars to pay attention to the preparation and investigation of properties of two-dimensional nanomaterials or nanostructures.As one of the quasi-one-dimensional nanostructures,nanoribbons generally have unique mechanical and photoelectric properties.In addition,because of its unique physical properties,2D nanomaterials or nanostructures have wide application in many fields.It is found that there are some limitations in practical applications of 2D nanomaterials or nanostructures.Researchers try to improve their properties by using two or more types of 2D nanomaterials or nanostructures to construct the van der Waals heterostructures held by the van der Waals force between layers or to construct intra-layer heterostructures.In such context,the mechanical and electronic properties of gallium nitride(Ga N)nanoribbons and 2D black phosphorus(blue phosphorus)/zinc oxide(Black P(Blue P)/Zn O)van der Waals heterostructures are studied by using density functional theory based first-principles computations.The main contents are as follows:(1)We use first-principles computations to search the most stable crystal structures and corresponding lattice constants of 2D Ga N,Black P,Blue P,and Zn O.(2)We construct the armchair and zigzag Ga N nanoribbons,and calculate the binding energies,edge energies,edge stresses and edge moduli of all kinds of Ga N nanoribbons,including passivated nanoribbons.It is found that the edges of Ga N nanoribbons were under compression.The edge stresses of Ga N nanoribbons decreased once the edges are passivated.The electronic band structures of zigzag Ga N nanoribbons with different edge configurations were also calculated.It is found that after passivation of both edges of the zigzag Ga N nanoribbons,the nanoribbons changed from conducting into semiconducting with indirect bandgap.(3)We construct the stable 2D Black P/Zn O and Blue P/Zn O van der Waals heterostructures,and calculate the elastic coefficients,piezoelectric coefficients,electronic band structures and density of states of the two heterostructures respectively.Our results show that by constructing the 2D van der Waals heterostructures,the piezoelectric properties as well as mechanical properties may get enhanced to certain degree.Our results in this work may provide some guildlines for the study of the physical mechanical properties and applications of 2D nanomaterials or nanostructures.