Design And Quantum Property Control For The ?-Group Two-dimensional Structure Materials

As we all known,the discovery of graphene makes the study for two-dimensional nano material of Group-? got leaps in progress,which also allows researchers have an interest of material properties and applications developed in ? family.The study shows that the high carrier mobility of graphene has been widely used in spin electronic materials,and its research on topological insulators has also made a great contribution.In this paper,we study the electronic properties and optical properties of the 2D structure materials by first-principles calculations.At the beginning,we first studied and calculated the structure and electronic properties of the stanene.This results show that the effect of strain can be changes the band gap at high symmetric K point,and the effect on the buckling constants is also significant.Then we can applying an electric field to stanene,and found which can open a big enough band gap at the?points.In addition,the band gap would have a regular change with the change of the electric field.Of course,the effective mass,Fermi velocity in the high symmetry points are different under different E-field.When we applying electric field and strain on the stanene,the results show that the band gap opening in stanene can be effectively modulated by the external E-field and strain,which make it develop in a direction we want to better.These results provide a good theoretical basis to effective regulation the band gap of stanene.Secondly,we studied the properties and electronic properties of germanene modified by functional group.We predict that when we modify germanene with different functional groups,which can make different results and let to different properties of germanene.In addition,the effect of the strain is sensitive for the germanene.In this case,we also take GeH as an example to conduct a more detailed study.This results shown that the effect of strain can enable GeH to realize band inversion at high symmetric points,while the quantum spin hall is only to open the band gap for GeH with 86 meV.In addition,by calculating Z₂,we find that the structure can be transition from the normal insulator to the topological insulator phase under exteral strain.At the same time,we also calculated the electronic properties of the Bilayer of functionalized germanene.And found that the properties of the bilay structure are very different from the monolayer.These results provide a theoretical basis for the application of topological materials in electronic devices.At the end of the study,we designed bilayer structure to verify its excellent electronic properties,which also provided more solutions for the application of germanene.The previous research has been around the hexagonal structure.In the last part,we studied the electronic properties and optical properties of XY₂?GeC₂,SnC₂?structure.The results show that this structure is a very stable structure both from dynamic stability and thermodynamic stability.When we apply strain and electric field,we can effectively adjust the gap size.In addition,in terms of the optical properties of the structure,both materials are very good isotropic materials and have good electron jump activity in the low-energy region.At the same time,by looking at the graph of its absorption function,we show that these two materials are very suitable for making ultraviolet detectors.