CN106400119A - Preparation method based on Co2MnGe/GaAs interface semimetal performance - Google Patents

Abstract

The invention provides a preparation method based on Co2MnGe/GaAs interface semimetal performance. The preparation method comprises following steps: 1, construction of the crystal structure of whole Heusler L21 type Co2MnGe is carried out, and optimization of the lattice structure is carried out; 2, under equilibrium lattice constant a<eq>, calculation and analysis of the state density of Co2MnGe are carried out; 3, construction and optimization of four interface structures in Co2MnGe/GaAs(111) direction are carried out; 4, calculation and analysis of the state density of the interface structure obtained after optimization are carried out; and 5, analysis and comparing are carried out so as to obtain an interface structure with semimetal performance.

Description

One kind is based on Co2The preparation technology of MnGe/GaAs interface Half-metallic

Technical field

The present invention relates to a kind of be based on Co₂The preparation technology of MnGe/GaAs interface Half-metallic.

Background technology

It has been found that many heusler alloys have semimetal characteristic, that is, spin passage be metallic and Another spin passage is semiconductive or insulating properties, thus showing 100% spin polarization.This exclusive characteristic makes this Class heusler alloy material becomes the optimal electronic spin injection source of quasiconductor.Therefore, in recent years, study Spencer Hawes Strangle alloy and the electronic structure of hetero-junctions of quasiconductor composition and its property causes the great interest of many researchers.Remove Outside this, the lattice structure of many heusler alloys and common semiconductor and lattice paprmeter are easy to mate, therefore these Huo Yi This is strangled alloy and is experimentally easy to be grown on common semiconductor.But it has to be mentioned that：Although these Haeussler types Half-metallic ferromagnet has good lattice match with some common quasiconductors, but when they form hetero-junctions, heterogeneous The interface of knot, the originally Half-metallic in bulk tends to lose, and that is, the interface of hetero-junctions does not have semimetal characteristic. The reason cause this result may is that many：As unordered, the oxidation of interface atom, the spin that defect causes scatters, Even intrinsic electron correlation effects.Either what reason, what this Half-metallic was degenerated at heterojunction boundary phenomenon All can be directly or indirectly owing to structural considerations.Be constantly present lattice mismatch after all between any two different materials can Can, even if their lattice structure and lattice paprmeter are very close.

For the problem of interface spin polarization between semi-metallic and quasiconductor, people theoretical and experimental Research.For example, Akbarzadeh et al. is based on Density functional theory study Co₂MnSi/GaAs and Co₂FeSi/GaAs hetero-junctions <001>The electromagnetic property in direction, finds in preferable SiMn/As interface Co₂Semimetal characteristic in MnSi bulk is still deposited , but Co₂This semimetal characteristic in FeSi bulk is then wholly absent in the interface with semiconductor GaAs.One with regard to Co₂The research report of CrAl/GaAs interface electronic structure：In Co₂CrAl/GaAs<110>On direction, the spin polarizability of electronics Often keep is of a relatively high, or even indivedual<110>100% almost can be reached in interfacial structure.Recently, Chadov et al. Using Haeussler material C o₂Two kinds of alloy structures of MnAl and CoMnVAl and compatibility chemically, by first principle Method reasonable design has gone out the magnetic resistance knot of high spin-polarization, confirms in theory in Co₂The interface of MnAl/CoMnVAl hetero-junctions Place shows semimetal characteristic.Experimentally, people are in substrate silicon（Si）Epitaxial growth goes out full heusler alloy Co₂FeSi is thin Film；In order to ensure ferromagnetic stability, with MgO as cushion, full heusler alloy Co₂MnSi study of thin film growth process is in ferrum （Fe）On substrate.By the magnetic circular dichroism of grenz ray（Soft x-ray magnetic circular dichroism, XMCD）, people have studied full heusler alloy Co₂The magnetic states of MnGe thin film Mn and Co atom in the case of rich Co.Therefore, from The practical application of spintronics devices is set out, the electromagnetic property of research semi-metallic and heterojunction semiconductor thin film（Especially It is the spin polarization at heterojunction boundary）It is very important.

Therefore, existing process method falls behind, and needs to improve.

Content of the invention

The technical problem to be solved be provide a kind of new based on Co₂MnGe/GaAs interface Half-metallic Preparation technology.

Technical scheme is as follows：One kind is based on Co₂The preparation technology of MnGe/GaAs interface Half-metallic, including Following steps：

The first step：Build full Haeussler L₂₁Type Co₂The crystal structure of MnGe, is optimized to its lattice structure, obtains balance Lattice paprmeter a_eq；

Second step：In balance lattice paprmeter a_eqUnder, to Co₂The density of states of MnGe is calculated and is analyzed, and determines bulk Co₂MnGe has good Half-metallic；

3rd step：?<111>Direction, builds semimetal Co₂Four kinds of interfacial structures of MnGe and semiconductor GaAs composition are simultaneously carried out Optimize, during optimizing, in order to as close as actual it is allowed to 5 layers of atom site relaxation about near interface, its He fixes atom site；

4th step：The density of states of the interfacial structure after calculation optimization is simultaneously analyzed, and draws the state of interfacial structure using graphic record Density, and be compared with the bulk density of states；

5th step：By analyzing and comparing, obtain the interfacial structure with semimetal characteristic.

Brief description

Fig. 1-a full Haeussler L₂₁Type Co₂The crystal structure of MnGe；

The density of states of Fig. 1-b monolithic structure, vertical dotted line represents Fermi surface；

Fig. 2 full Haeussler L₂₁Type Co₂MnGe and semiconductor GaAs exist<111>Direction interfacial structural model；

Fig. 3 Co₂MnGe/GaAs<111>The total state density of the four kinds of interfacial structures in direction, dash area is corresponding in monolithic structure The density of states of atom, vertical dotted line represents Fermi surface；

Fig. 4 present invention process flow chart.

Specific embodiment

For the ease of understanding the present invention, below in conjunction with the accompanying drawings and specific embodiment, the present invention will be described in more detail. The preferred embodiment of the present invention is given in this specification and its accompanying drawing, but, the present invention can be in many different forms To realize the embodiment however it is not limited to described by this specification.On the contrary, providing the purpose of these embodiments to be to make to the present invention Disclosure understanding more thoroughly comprehensive.

It should be noted that when a certain element is fixed on another element, another including this element is directly fixed on this Individual element, or this element is fixed on this another element by least one other element placed in the middle.When an element connects Connect another element, be directly connected to this another element including by this element, or it is placed in the middle that this element is passed through at least one Other elements be connected to this another element.

One kind is based on Co₂The preparation technology of MnGe/GaAs interface Half-metallic, comprises the following steps：

The first step：Build full Haeussler L₂₁Type Co₂The crystal structure of MnGe, is optimized to its lattice structure, obtains balance Lattice paprmeter a_eq；

Second step：In balance lattice paprmeter a_eqUnder, to Co₂The density of states of MnGe is calculated and is analyzed, and determines bulk Co₂MnGe has good Half-metallic；

3rd step：?<111>Direction, builds semimetal Co₂Four kinds of interfacial structures of MnGe and semiconductor GaAs composition are simultaneously carried out Optimize, during optimizing, in order to as close as actual it is allowed to 5 layers of atom site relaxation about near interface, its He fixes atom site；

4th step：The density of states of the interfacial structure after calculation optimization is simultaneously analyzed, and draws the state of interfacial structure using graphic record Density, and be compared with the bulk density of states；

5th step：By analyzing and comparing, obtain the interfacial structure with semimetal characteristic.

The material simulation software WIEN2K of worldwide earthquake disaster (FPLAPW) method based on first principle, I To full Haeussler L₂₁Type Co₂MnGe bulk and its surface nature are simulated calculating.The parameter being adopted is as follows：With block The relevant parameter of energyR _mt K _maxIt is taken as 7.5, Co, Mn, the muffin-tin radius of Ge, Ga and As atom is taken as 2.2,2.1 respectively, 2.0,2.3 and 2.3 a.u., using the exchange correlation functional of GGA-PBE form and consider relativistic effect, tie to interface Structure first Brillouin-Zone integrates setting 14 × 14 × 1kPoint, being certainly in harmony the convergence criterion of circulation is 10^-5Ry/f.u.；In order to than Co is relatively described₂The difference of electromagnetic property in MnGe and GaAs bulk and interfacial structure, we also utilize the parameter pair of above-mentioned setting The property of bi-material bulk is calculated, except first Brillouin-Zone integration is arranged for 14 × 14 × 14kPoint.

First, as Fig. 1（a）Shown, we build full Haeussler L₂₁Type Co₂MnGe crystal structure is simultaneously optimized acquisition It balances lattice paprmeter, a₀=5.8037 Å.Based on this, we are using lattice paprmeter a optimizing₀=5.8037 its bulk of calculating Electromagnetic property, its density of states such as Fig. 1（b）Shown, from Fig. 1（b）We are clear that the Co of bulk₂MnGe has bright Aobvious semimetal characteristic, that is, the passage spinning up have passed through Fermi surface, shows metallic character, and the downward passage that spins is in Fermi There is the energy gap of an about 0.7eV near face, there is obvious characteristic of semiconductor.

Next, we pay close attention to semimetal Co₂MnGe and the electromagnetic property at semiconductor GaAs interface.Based on us State the monolithic structure of optimization, we build Co₂Four kinds of MnGe/GaAs (111) direction interfacial structure.Fig. 2 is with semimetal Co₂The As atom in Ge atom and semiconductor GaAs in MnGe is the interfacial structure of boundary layer atom, is designated as Ge-As interface, It is one representative model of four kinds of interfacial structures.Other three kinds of structures are with semimetal Co respectively₂Ge, CoMn atom in MnGe and As, Ga atom in semiconductor GaAs is the interfacial structure of boundary layer atom, and for convenience of describing, we are designated as respectively：Ge-Ga、 CoMn-As and CoMn-Ga interface.Due to four kinds of interfacial structures model be similar to, still only draw Ge-As interface in fig. 2 Represent as one.What deserves to be explained is：?<111>Direction, Co₂MnGe has four kinds of end faces, and according to our former calculating, Only two surfaces of Ge and CoMn have Half-metallic, still only consider two kinds of Ge and CoMn in the case of interfacial structure, that is, and GaAs forms four kinds of interfacial structures.In addition, for these four interfacial structures of theoretical modeling and studying its physical property, we are to every kind of different Matter knot exists<111>One Co comprising 17 atomic layers is constructed on direction₂The thin film of the PbS of VGa and 13 atomic layer.? Before calculating property, we carry out structure optimization to these four interfaces first：The atom site allowing 5 layers about near interface relaxes Henan, other atom sites are fixed.After structure optimization, we calculate the electromagnetic property of this four kinds of structures, its density of states figure such as Fig. 3 institute Show.Meanwhile, in order to compare monolithic structure and the electro qualitative difference of surface texture, the atomic state also depicting corresponding bulk is close Degree.From Fig. 3, it may be seen that a stem-winding phenomenon：Ge-As interface maintains the semimetal characteristic in bulk, The electronics spinning up shows metallic character and the downward electronics that spins has an energy gap near Fermi surface, shows absolutely Edge；And, Ge-Ga interface also shows nearly semimetal attribute；However, for other two kinds of interface C oMn-As and CoMn-Ga Interface, due to the presence of interfacial state, the semimetal attribute in bulk is destroyed.As can be seen here, by us to four kinds of interfaces The structure of structure and the analysis to its density of states, Ge-As and Ge-Ga can regard at two interfaces up-and-coming as and be applied to certainly The thin-film material of rotation electronics device.

It should be noted that above-mentioned each technical characteristic continues to be mutually combined, form the various embodiments not being enumerated above, It is accordingly to be regarded as the scope of description of the invention record；And, for those of ordinary skills, can add according to the above description To improve or to convert, and all these modifications and variations all should belong to the protection domain of claims of the present invention.

Claims (1)

1. one kind is based on Co₂The preparation technology of MnGe/GaAs interface Half-metallic is it is characterised in that comprise the following steps：

The first step：Build full Haeussler L₂₁Type Co₂The crystal structure of MnGe, is optimized to its lattice structure, obtains balance Lattice paprmeter a_eq；

Second step：In balance lattice paprmeter a_eqUnder, to Co₂The density of states of MnGe is calculated and is analyzed, and determines bulk Co₂MnGe has good Half-metallic；

3rd step：?<111>Direction, builds semimetal Co₂Four kinds of interfacial structures of MnGe and semiconductor GaAs composition simultaneously carry out excellent Change, during optimizing, in order to as close as actual it is allowed to 5 layers of atom site relaxation about near interface, other Atom site is fixed；

4th step：The density of states of the interfacial structure after calculation optimization is simultaneously analyzed, and draws the state of interfacial structure using graphic record Density, and be compared with the bulk density of states；

5th step：By analyzing and comparing, obtain the interfacial structure with semimetal characteristic.