Construction And Properties Tuning Of Single-layer Two-dimensional Nanostructures

Single-layer two-dimensional nanostructures have many excellent properties and broad application prospects,due to the ultra-thin thickness.It is particularly important to prepare single-layer two-dimensional nanostructures and achieve properties tuning.In this paper,construction and properties tuning of single-layer two-dimensional nanostructures are mainly achieved through experimental and theoretical methods,as follows:1)Single-layer two-dimensional nanostructures of biomolecule 5-aminopyrimidine[4,5-d]pyrimidine-2,4(3H,8H)-dione(AT)formed on silver surface were observed by room temperature ultra-high vacuum scanning tunneling microscope(STM),using it as a molecular template to tune fullerene nanostructures.Using cyclic self-assembly structure of AT molecules on the Ag(111)surface,a fullerene cyclic nanostructure was constructed.Using large-area chain single crystal of AT molecules formed on the Ag(110)surface,a fullerene linear structure was constructed,and the length of fullerene in linear structure varies on the molecule,but their directions all are 40 degrees from the molecular chain.2)Using first principle based on density functional theory,revealing that charge doping is an effective way of tuning the ferroelectricity of single-layer group IV chalcogenide MX(M=Ge,Sn;X=S,Se).Calculation shows that hole doping can weaken or even completely suppress the ferroelectric polarization in SnSe,that is,the ferroelectric phase changes to paraelectric phase.This property can be explained by the change in bond strength with charge doping in the material.In addition,charge doping can effectively change the lattice constants of MX,indicating that these two-dimensional materials are suitable for constructing van der Waals heterojunctions with other two-dimensional materials,and the moire period can be effectively tuned by charge doping.