Result Prediction And Physical Properties Of Two-Dimensional Germanium Based Materials

The emergence of graphene has greatly stimulated researchers’interest in two-dimensional（2D）nanomaterials.Different from the bulk materials,the thickness of two-dimensional nanomaterials is only at the nanometer level.The electrons bound in a 2D plane are affected by the quantum effect,which makes nanomaterials have excellent optical,electrical and mechanical properties,making them the ideal materials for preparing micro nanodevices in the future.In this paper,according to the first-principles calculations,three stable 2D germanium based nanomaterials are theoretically predicted.The research emphases are as follows:First of all,at the nanometer scale,molecular assembly is a method to design new materials.Inspired by this,we use digermyl ether assembly to obtain a 2D nanomaterial named germanether.Its stability has been verified by the calculation of binding energy,phonon spectrum,thermodynamics and elastic constants.Its band gap can be tuned by strain and double-layer stacking,and both can be used to obtain a direct band gap.In addition,germanether exhibits a unique in-plane negative Poisson’s ratio in terms of mechanical properties.Finally,the molecular dehydrogenation and diffusion process on silver（100）surface was calculated.Secondly,based on the idea of isoelectronic substitution,we theoretically predicted the 2D Ge₂S.Ge₂S is an indirect band gap（1.54 e V）semiconductor,which can transform from indirect band gap to direct band gap under uniaxial strain.It has strong absorption characteristics for ultraviolet light.In addition,the calculations of elastic constant and strain fitting prove that Ge₂S is an auxetic material,which broadens its application in textile,military and other fields.Finally,inspired by the properties of silicene and germanene oxides,we theoretically predicted the 2D nanomaterial Si Ge O.The binding energy,phonon spectrum and thermodynamics confirmed its stability.Si Ge O is an indirect band gap（1.29 e V）semiconductor and possesses high electron mobility.Its band has an indirect-direct gap transition under uniaxial strain,and exhibits robustness to external electric fields.In addition,Si Ge O shows good absorption characteristics for ultraviolet to near-infrared wavelengths,showing that it can be widely used in optical devices.Finally,the relationship between lattice constants changed under strain is fitted,and the results show that single-layer Si Ge O belongs to auxetic material.