Theoretical Investigation On Modulating Electronic And Magnetic Properties Of Si C Nanoribbons Via Surface-modified Approaches

The successful fabricated of grapheme in the experiment,opened up another golden age of nano-materials research.Due to the reduction of dimension,the graphe ne and its derivatives manifest many fascinating features which are not available in the traditional materials.These peculiar properties of graphene show the broad application prospect of low-dimensional and become one of the hot topics in the field of materials.With the rapid improvement of computer performance and the more advanced computer simulation methods,researchers can accurately design and simulate the geometry,physical and chemical properties of low dimensional nano-materials.The pursuit of high-performance materials is the goal of researchers unremitting efforts.In the one dimension nano-materials,silicon carbide nanoribbon has the similar structure to the graphene nanoribbon and owns the unique electronic and magnetic properties,its superior thermal stability,chemical stability and good processing performance have attracted a lot of attentions in the both theoretical and experimental researchers and have wide application prospects in the field of nanodevices.Based on the systematic density functional theory?DFT?computations,we explored the geometries,stabilites,electeic and magnetic properties of the Si CNRs surface-modified by ferroelectric polymer poly?vinylidene fluoride??PVDF?,3d transion metal and magnetic superhalogen MnCl₃,respectively.The functional modification of the materials is the most effective way to broaden the application prospects of the materials,and surface modification is one of the idea strategies to improve the properties of materials without damaging the intrinsic structure and original properties of the materials.The findings are briefly summaried below:we propose a simple and effective strategy to modulate the electronic and magnetic behaviors of zSiCNRs through noncovalently surface-adsorbing a PVDF polymer,which ultilizing the intrinsic dipole and electron-withdrawing abilities of PVDF break the magnetic degeneracy of FM and AFM states in pristine zSi CNRs.The computed results reveal that the PVDF polymer can stablely asorbed the surface of zSi CNRs,which the adsorption energies are in the range of-0.436^-1.315 e V.Due to the electron transfer from the zSiCNR to PVDF,it make the electronstatic potential of the surface of zSi CNRs has an e vidently increase,and effectively tune the bandstructure of zSiCNRs,which is the mainly responsible for the destruction of magnetic degeneracy of zSiCNR.The magnetic degeneracy of all the systems that the PVDF adsorbed with different spatial configurations and adsorption sites can be broken effectively,and the sole ferromagnetic metallicity and antiferromagenetic half-metallicity can be achieved.The TM atoms possess the unique d electronic structure and intrinsic magnetic moment.We have performed the detailed density functional theory computations to investigate the structures,electronic and magnetic properties of zSi CNR by surface-adsorbing TM atoms?TM=Ti,Cr,Mn,Fe and Co?in this work.The computed results reveal that when adsorbing the 3d-TM atoms at the ribbon center,the magnetic degeneracy of zSi CNR can be broken,which is due to the case where the electron transfer process occurs from TM atoms to the substrate,resulting in the decrease of the electrostatic potential of zSiCNR.Further,it is revealed that a similar situation can be maintained in the TM-modified zSi CNR systems with different widths.When moving the TM atoms from the center to the edge of ribbon,the magnetic degeneracy of zSi CNR can be still destroyed,and the solely FM or AFM half-metallicity can be observed in these modified zSi CNR systems with TM atoms at the edge.The adsorption sites of TM atoms adsorbed at the center,C edge and Si edge of ribbon are different,due to the different chemical active of center and edge of the ribbon and coordinate number of d electron.All the TM atoms can stably adsorbed on the surface of ribbon,which the adsorption energy in the range of-0.872^-4.304 e V,indicating their high structure stabilities.Obviously,surface-adsorbing 3d-TM atoms can be an effective strategy to modulate the electronic and magnetic behaviors of pristine zSi CNRs.These interesting findings will promote the practical application of Si C-based nanomaterials.Superhalogen is a group or molecule that has higher electron affinity than the halogen atom.The more electronegativity and no vel properties make superhalogen can use as building block for new high energy density material with good safety and stable performance.In the past few years,people focused on how to design and synthesize new types of superhalogens,but how to use the superhalogen to control the physical and chemical properties and enhance the functionalization of the materials is an area that has not been studied yet.Therefore,we detailed studied the effect of magenetic superhalogen surface-modified zigzag-and armchair-Si CNR on the geometry structures,electronic and magnetic properties,respectively.The computed results reveal that when the MnCl₃ adsorbed at the surface of ribbon,it can introduce the magnism to the substrate Si CNR,and induce the increase of electrostatic potential of ribbon plane,accompanying the electron transfer from the Si CNR to MnCl₃.It can effectively break the magnetic degeneracy of zSi CNRs and o btain the sole FM metallicity and FM half-metallicity.Comparatively,the simeconductor of aSi CNR is tuned to be moderate FM half-metallicity and FM SGS.We investigate the modified systems that MnCl₃ adsorbed at edge of zSi CNRs and aSiCNR,respectively,the steady the FM half-metallicity and FM SGS are independence of the ribbon width.All the modified systems exhibit thermodynamic stability and the adsorption energies are in the range of-1.430^-3.915 e V.