Regulation Of Strain On Electronic Properties Of Two-Dimensional Germanium Selenide Isomers

The two-dimensional material GeSe has a similar warping geometry with phosphonene and has a rich isomer structure.Since the discovery of phosphoenene,various excellent electronic properties have been explored,and related research has attracted wide attention of scholars.Mono-layer GeSe with similar structure to phosphoenene has also attracted extensive attention.In this paper,the first-principles calculation method is used to control the band gap of monolayer GeSe isomers by applying strain,the effects of strain on their electronic properties are discussed.The main conclusions obtained are:?1?The stability study of five isomer structures of two-dimensional GeSe was carried out,and the stability prediction was carried out by calculating the binding energy and vibration frequency.By analyzing the binding energy,it was found that the binding energy between the five structures did not exceed 0.06 eV/atom.The stability of the structure is also judged by calculating the vibration frequency and the zero point energy and analyzing the virtual frequency occupying the zero point energy.It was found that?-GeSe has a stable geometry of a hexagonal lattice,and the other four structures are orthorhombic.The energy band structures of five two-dimensional GeSe structures were calculated by PW91 and HSE06 hybrid functional methods.The results show that?-GeSe is a semiconductor with a direct band gap,and the energy bands of the other four structures are all indirect band gap types.?2?The energy band structure of five isomers of two-dimensional GeSe was studied by applying uniaxial or biaxial strain.It is found that?-GeSe undergoes direct-indirect band gap conversion and semiconductor-to-metal transition under strain control;?-GeSe and?-GeSe have adjustable band gap range under strain;A direct band gap in?-GeSe is found under the biaxial compression strain of?_xy=-2%and?_xy=-4%;by applying 10%tensile strain along the armchair direction of?-GeSe,indirect to direct band gap occurs,the transformation continues to increase the tensile strain to 20%,and the band structure maintains the characteristics of the direct band gap.When a 10%tensile strain is applied along the?-GeSe biaxial,the structure also undergoes an indirect to direct transition,which is maintained until the biaxial tensile strain increases to 19%,with an adjustable range of 0.61 eV¹.19eV.?3?The mono-layer?-GeSe was studied under the large strain range,and its geometry and stability under large strain conditions were discussed.The results show that under the tensile stress of 20%in the armchair,zigzag and biaxial directions,the ratio of the virtual frequency of the structure to the zero point energy is 0.16%,0.02%and 0.03%,respectively.Thermodynamic stability is still obtained under 20%tensile stress.