First-principles Calculation Study On Modification Of Graphene/MoS₂ Heterojunction

Both graphene and MoS₂ have been used in many applications,but since graphene has a zero band gap,there are many limitations in the development in the electronic field.MoS₂ is sensitive to light and has a similar structure to graphene,which can be lattice-macthed.The heterojunction of MoS₂ and graphene can exist stably and absorb the advantages of both MoS₂ and graphene,but the band gap of the graphene/MoS₂heterojunction is small,only a few tens of me V.Therefore,the band gap of the graphene/MoS₂heterojunction can be adjusted by hydrogenation and vacancy defects to make it have more different properties,and further broaden the application of the graphene/MoS₂ heterojunction.Through the CASTEP module in the Materials Studio software,a three-dimensional structure model of the graphene/MoS₂ heterojunction was constructed.In order to study the influence of hydrogenation on the photoelectric properties of graphene/MoS₂ heterojunction,we added different numbers of hydrogen atoms on the surface of graphene or upper and lower surfaces of graphene/MoS₂heterojunction.In order to study the co-effect of C atom vacancy defects and hydrogenation,we introduced C atom vacancy defects into the graphene single-sided hydrogenated graphene/MoS₂ heterojunction.By calculating the lattice constant,binding energy,energy band structure,total density of states and light absorption coefficient,the effects of hydrogenation,the co-effects of hydrogenation and C atom vacancies on the structure,stability,electronic properties and optical properties of the heterojunction are analyzed.The studied results show that the band gap of the graphene/MoS₂ heterojunction itself is small.After more hydrogen atoms are added to the upper and lower surfaces,the energy gap of the heterojunction is opened,and the more hydrogen atoms are added,the larger the energy gap.Hydrogenation is only performed on the graphene surface of the heterojunction,and the energy gap of the heterojunction also can be opened,especially after adding 8 hydrogen atoms,the band gap of the heterojunction becomes1.076 e V,which appears as a semiconductor.It shows that hydrogenation of the graphene/MoS₂ heterojunction system can change the band gap of the heterojunction.After forming a heterojunction between MoS₂ and graphene,the light absorption peak near 220 nm appears in the ultraviolet region,and light absorption is mainly concentrated between 200nm-280nm.After hydrogenating the surface of the graphene/MoS₂ heterojunction,the position of the light absorption peak did not change.At the same time,the light absorption rate in the visible light region increases after hydrogen is absorbed,and the more hydrogen atoms are added,the higher the light absorption rate in the visible light region.C atom vacancy defects can change the structure and electronic properties of the hydrogenated graphene/MoS₂ heterojunction,but have little effect on the optical properties.After the introduction of C atom vacancy defects,the atoms around the vacancies in the graphene single-sided hydrogenated graphene/MoS₂ heterojunction all move closer to the vacancies.The heterojunction structures are stable,and all behave as semiconductors.The C atom vacancy defect can reduce the band gap of the hydrogenated graphene/MoS₂ heterojunction,and the position of the C atom vacancy defect has a greater impact on the band gap adjustment.This indicates that C atom vacancy defects can be used as a means of fine tuning the band gap of hydrogenated graphene/MoS₂ heterojunction.The light absorption peak of the hydrogenated graphene/MoS₂heterojunction with C vacancy defects is around 220nm,and the light absorption is concentrated between 200nm-280nm in the ultraviolet region.It shows that the introduction of C atom vacancy defects does not change the position of the light absorption peak.