First-principle Study Of Defect Effect On Photoelectric Properties Of Superlattices Of Two-dimensional Silicene Materials

Electrons have both charge and spin intrinsic characteristics corresponding to traditional electronics and spintronics.The latter solves the current leakage and heat dissipation problems due to limited dimensions caused by the former.Spin,such degree of freedom has been introduced into semiconductor devices and a series of new spintronic devices have been manufactured,promoted the explorations of magnetic semiconductor materials throughout the condensed physics.Magneto-optical Kerr effect promotes the development of spintronics with the essence of the spin dependent of light.In recent years,researches have shown that the spin dependent optical properties have important applications in spin-polarized transport,spin photocurrent and pure spin current.It is of great significance to search for magnetic semiconductor materials with strong light response of single spin to expand the development of spin optoelectronics.The two-dimensional nanomaterials represented by graphene have penetrated into various scientific fields with an extremely fast speed since graphene had been prepared experimentally.Silcene with its exotic electronic properties and unique potential,especially the compatibility with silicon-based electronic devices,may follow this trend and open up new applications.If strong spin-dependent optical response could be obtained in silicon-based systems,the applications in practical optoelectronic spin devices will be further expanded.Given the huge potential of silicene,based on two-dimensional transverse heterojunction and surface functionalization progress in experiment and theory,we built a two-dimensional composite structure superlattice based on armchair silicon-based materials.At the same time,considering the effects of defect on photoelectric properties,we calculated the regulating effects of different defects on superlattices.Firstly,the electronic and optical properties of the transition metal adsorption on armchair silcene/silcsane superlattice(A-SSSLS)were studied.It is found that the adsorption of both Fe and Cr atoms can effectively regulate the band gap by controlling the width of the silicene region,and introduces magnetic properties while obtaining a strong spindependent light absorption property.Secondly,we studied the substitution doping effects of non-metallic light atoms B and N on A-SSSLS and found that it exhibites rich electronic properties and magnetism of semiconductor,metal or semi-metal depending on the degree of hydrogenation.The absorption peak A of the first shoulder structure in the imaginary part of the dielectric function shows obvious red shift after doping and B doping significantly enhances infrared region light absorption peak while N doping does not.As the only magnetic semiconductor,N-(7,3)-SSSLS possesses spin dependent opticals,but its application in practical optoelectronic devices is limited due to the small energy difference between the spin channel and low absorption peak intensity.Finally,we constructed the half-hydrogenated silicene/silicane superlattices(A-HSSSLS)and studied the adsorption effects of alkali and transition metals.The results show that although the alkali metal atom doped A-HSSSLS does not enhance the optical absorption,it produces more obvious spin-resolved optical properties,which has a greater potential in the application of spin-optical semiconductor devices.For the adsorption of seven kinds of transition metals on A-HSSSLs,Cr adsorption shows increased absorption optical properties of single spin channel,which provides a theoretical basis for the application of A-HSSSLs in spin optoelectronic devices.