Effects Of Interface And Stacking On Mechanical Properties And Electronic Structure Of Fe₃Si/GaAs Heterostructures

As a binary Heusler alloy,Fe₃Si has a simple structure and is easier to prepare.At the same time,Fe₃Si has become a promising material in spin electronics due to its high Curie temperature and spin polarization.The lattice constant of Fe₃Si is very similar to GaAs.At a temperature of up to 200?C,Fe₃Si/GaAs heterostructure of high crystal and interfacial perfection can be fabricated by molecular beam epitaxy.This paper introduce the basic properties and current research status of Fe₃Si,list the theories used in this article,elaborate the effects of stacking and interface on the mechanical and electronic structure of Fe₃Si/GaAs heterostructure.The research content and results of this article are as follows:The surface models of Fe₃Si and GaAs were relaxed,determine the number of con-vergent surface structure layers,and establish four kinds of Fe₃Si/GaAs heterostructure models,including?0 0 1?interface with hollow-site,?0 0 1?interface with top-site,?1 10?interface with hollow-site and?1 1 0?interface with top-site.The density functional theory was used to calculate the structure,surface energy,interfacial energy,adhesion work,density of states,the charge density difference and charge density of Fe₃Si/GaAs heterostructure.The calculated results show that:?1?for the same interface,hollow-site has larger adhesion work and smaller interfacial energy than top-site;?2?for the same stacking method,the?0 0 1?interface has larger adhesion work and smaller interface en-ergy than the?1 1 0?interface.When the Fe₃Si?1 1 0?is overgrown in the GaAs?1 1 0?,the rippled surface is destroyed,which reduces the adhesion work;?3?Among the four heterostructure models,the mechanical properties and ductility of the?0 0 1?interface with hollow-site are the strongest.At the same time,it has minimal interfacial energy and is easier to form.We also discussed the contribution of the electronic structure of the?0 0 1?interface with hollow-site and the orbital hybridization to covalent bond formation at the interface.?1?There are both covalent and metal bonds in Fe₃Si,and there is a covalent bond between Ga and As atoms in GaAs.The obvious charge accumulation at the interface indicates that Fe atom and Si atom form a covalent bond with As atom.Since As?2.18?has a larger electronegativity between Fe?1.83?and Si?1.90?,most of the charge accumulates in the As position,resulting in interface bonding.?2?Comparing with the top-site model and the hollow-site model,only one As atom is bonded to one Fe atom and there is no bond between the As atom and the Si atom at the top-site model;an As atom is bonded to two Fe atoms and two Si atoms at the interface of hollow-site model.The hollow-site model has a larger contact area than the top-site model,and the As atom can contact more atoms to form more bonds,making the interface more stable.For the hollow-site model,since Fe and Si are metal element and metalloid element respectively,the electronegativity of Fe is lower than that of Si.Therefore,Fe is more likely to lose valence electrons than Si in the bonding process,resulting in a Fe-As bond being stronger than the Si-As bond.?3?Hybridization of Fe?s and d?and As?p?,Si?s and p?and As?p?play a major role in the formation of covalent bonds.The rearrangement of the interface charge is mainly limited to the first layer at the interface.The rearrangement of the charge near the interface causes Fe,Si and As electrons to hybridize to form covalent bonds.In this paper,through theoretical comparison of four heterostructures of Fe₃Si/GaAs,we find the most stable heterostructure in theory.We analyzed the effect of electron distri-bution on the mechanical properties of the structure,and provided theoretical guidance for the preparation of a more stable Fe₃Si/GaAs heterostructure experimentally.