Theoretical Research On Performance Regulation Of New Two-dimensional Group-? Monochalcogenides Materials

The first principles calculation based on density functional theory is an important method to carry out theoretical research on condensed matter.We use this method to do a systematic theoretical study of two-dimensional group-IV monochalcogenides compounds represented by GeSe.First,the single-layer GeSe is chosen as preliminary object of study because of its direct band gap and small effective carrier mass.In practice,these features give it better performance.On this basis,we investigate the tunable electronic and magnetic properties of single-layer GeSe decorated with light non-metal atoms(H,F,Cl)at different high symmetry sites.From our results,we can see that,in H adatom-decorated system,the electronic property of GeSe monolayer can be effectively manipulated,and keeps the direct band gap in most situations.H adatom-decorated structures have dilute magnetic states.Most of them cause a bipolar semiconducting behavior,while the rest owns a spin-gapless-semiconducting feature.Meanwhile,in F and Cl adatom-decorated systems,the magnetism appears only in F adatom-decorated D-Se structure.For most of the F and Cl adatom-decorated systems,they own p-type semiconducting feature.These results demonstrate that the decoration for GeSe is an available approach to tune its electronic and magnetic properties.After the modification,the GeSe monolayer shows desirable potential in the application of spintronics and optoelectronic devices.In view of the majority of two-dimensional group-IV monochalcogenides compounds are indirect band gap semiconductors.We construct four high symmetric bilayer stacking models to regulate their electronic property.After systematically exploring the dynamical and thermal stabilities of all bilayer structures,we screened out the system that is likely to be stable at room temperature.Then,the first-principles calculations are used to investigate how bilayer structures affect their properties.The results show that forming two-dimensional bilayer group-IV monochalcogenides compounds can make its electronic properties are effectively adjusted.With this method,their band gap values enable wide-spectrum regulation between 0.789 and 1.617 eV.And there are three cases achieving the indirect-direct band gap transition.Furthermore,given the flexibility of these materials,we apply in-plane uniaxial tensile stresses to tune their band structure and obtain more indirect-direct band gap transitions.The implementation of direct band gap will be beneficial to the application in the next generation of highly efficient modern nanoelectronics and photovoltaic devices.We also study the response of different bilayer group-IV monochalcogenides compounds to external vertical electric fields.The results show that under the combined effect of interlayer polarization and the giant Stark effect,they exhibit weaker resistance to external electric fields.