CN117265483A - High-coercivity hard magnetic oxide semiconductor film with perpendicular magnetic anisotropy and preparation method thereof - Google Patents
High-coercivity hard magnetic oxide semiconductor film with perpendicular magnetic anisotropy and preparation method thereof Download PDFInfo
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- 230000005291 magnetic effect Effects 0.000 title claims abstract description 38
- UCNNJGDEJXIUCC-UHFFFAOYSA-L hydroxy(oxo)iron;iron Chemical compound [Fe].O[Fe]=O.O[Fe]=O UCNNJGDEJXIUCC-UHFFFAOYSA-L 0.000 title claims abstract description 15
- 239000004065 semiconductor Substances 0.000 title claims abstract description 15
- 238000002360 preparation method Methods 0.000 title abstract description 27
- 229910005949 NiCo2O4 Inorganic materials 0.000 claims abstract description 39
- 238000000034 method Methods 0.000 claims abstract description 36
- 230000008569 process Effects 0.000 claims abstract description 12
- 238000004544 sputter deposition Methods 0.000 claims abstract description 12
- 239000010408 film Substances 0.000 claims description 103
- 239000000758 substrate Substances 0.000 claims description 43
- 238000000151 deposition Methods 0.000 claims description 27
- 239000013077 target material Substances 0.000 claims description 27
- 239000010409 thin film Substances 0.000 claims description 24
- 229910026161 MgAl2O4 Inorganic materials 0.000 claims description 20
- 229910052596 spinel Inorganic materials 0.000 claims description 20
- 230000008021 deposition Effects 0.000 claims description 19
- 238000001755 magnetron sputter deposition Methods 0.000 claims description 19
- 229910003264 NiFe2O4 Inorganic materials 0.000 claims description 16
- NQNBVCBUOCNRFZ-UHFFFAOYSA-N nickel ferrite Chemical compound [Ni]=O.O=[Fe]O[Fe]=O NQNBVCBUOCNRFZ-UHFFFAOYSA-N 0.000 claims description 16
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 13
- 239000001301 oxygen Substances 0.000 claims description 13
- 229910052760 oxygen Inorganic materials 0.000 claims description 13
- 239000013078 crystal Substances 0.000 claims description 12
- 239000000919 ceramic Substances 0.000 claims description 11
- 238000000137 annealing Methods 0.000 claims description 8
- 238000005245 sintering Methods 0.000 claims description 8
- 229910052742 iron Inorganic materials 0.000 claims description 7
- 238000002425 crystallisation Methods 0.000 claims description 6
- 230000033228 biological regulation Effects 0.000 claims description 5
- 230000008025 crystallization Effects 0.000 claims description 5
- 238000011065 in-situ storage Methods 0.000 claims description 5
- 238000004519 manufacturing process Methods 0.000 claims description 5
- 230000008859 change Effects 0.000 claims description 4
- 238000001816 cooling Methods 0.000 claims description 3
- 230000007547 defect Effects 0.000 claims description 3
- 238000009826 distribution Methods 0.000 claims description 3
- 230000005415 magnetization Effects 0.000 claims description 3
- 238000005457 optimization Methods 0.000 claims description 3
- 230000003647 oxidation Effects 0.000 claims description 3
- 238000007254 oxidation reaction Methods 0.000 claims description 3
- 230000002159 abnormal effect Effects 0.000 abstract description 7
- 230000008901 benefit Effects 0.000 abstract description 4
- 230000009286 beneficial effect Effects 0.000 abstract description 3
- 230000015654 memory Effects 0.000 abstract description 3
- 238000012827 research and development Methods 0.000 abstract description 3
- 238000011161 development Methods 0.000 abstract description 2
- 229910006072 NiFeO4 Inorganic materials 0.000 abstract 1
- 238000005516 engineering process Methods 0.000 abstract 1
- 230000001737 promoting effect Effects 0.000 abstract 1
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 21
- 239000000696 magnetic material Substances 0.000 description 16
- 230000001276 controlling effect Effects 0.000 description 8
- 239000000463 material Substances 0.000 description 8
- 239000000843 powder Substances 0.000 description 7
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 4
- 229910003266 NiCo Inorganic materials 0.000 description 4
- 230000005293 ferrimagnetic effect Effects 0.000 description 4
- UPWOEMHINGJHOB-UHFFFAOYSA-N oxo(oxocobaltiooxy)cobalt Chemical compound O=[Co]O[Co]=O UPWOEMHINGJHOB-UHFFFAOYSA-N 0.000 description 4
- 238000003860 storage Methods 0.000 description 4
- 238000002156 mixing Methods 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 238000003825 pressing Methods 0.000 description 3
- 230000004044 response Effects 0.000 description 3
- 230000005641 tunneling Effects 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 238000002441 X-ray diffraction Methods 0.000 description 2
- 229910052786 argon Inorganic materials 0.000 description 2
- 238000000498 ball milling Methods 0.000 description 2
- 238000001514 detection method Methods 0.000 description 2
- 239000007789 gas Substances 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- GNMQOUGYKPVJRR-UHFFFAOYSA-N nickel(III) oxide Inorganic materials [O-2].[O-2].[O-2].[Ni+3].[Ni+3] GNMQOUGYKPVJRR-UHFFFAOYSA-N 0.000 description 2
- PZFKDUMHDHEBLD-UHFFFAOYSA-N oxo(oxonickeliooxy)nickel Chemical compound O=[Ni]O[Ni]=O PZFKDUMHDHEBLD-UHFFFAOYSA-N 0.000 description 2
- 229910052573 porcelain Inorganic materials 0.000 description 2
- 230000001105 regulatory effect Effects 0.000 description 2
- 229910000531 Co alloy Inorganic materials 0.000 description 1
- 229910019236 CoFeB Inorganic materials 0.000 description 1
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 1
- ZDZZPLGHBXACDA-UHFFFAOYSA-N [B].[Fe].[Co] Chemical compound [B].[Fe].[Co] ZDZZPLGHBXACDA-UHFFFAOYSA-N 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- 230000002547 anomalous effect Effects 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
- 230000001427 coherent effect Effects 0.000 description 1
- 229910052593 corundum Inorganic materials 0.000 description 1
- 230000008878 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
- 230000007812 deficiency Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 230000005294 ferromagnetic effect Effects 0.000 description 1
- 230000005350 ferromagnetic resonance Effects 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 238000009776 industrial production Methods 0.000 description 1
- 230000010354 integration Effects 0.000 description 1
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 238000000059 patterning Methods 0.000 description 1
- 239000012071 phase Substances 0.000 description 1
- 230000010287 polarization Effects 0.000 description 1
- 238000004549 pulsed laser deposition Methods 0.000 description 1
- 238000005086 pumping Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 238000007493 shaping process Methods 0.000 description 1
- 239000007790 solid phase Substances 0.000 description 1
- 238000005477 sputtering target Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
- 238000004506 ultrasonic cleaning Methods 0.000 description 1
- 229910001845 yogo sapphire Inorganic materials 0.000 description 1
Classifications
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
- C23C14/22—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the process of coating
- C23C14/24—Vacuum evaporation
- C23C14/28—Vacuum evaporation by wave energy or particle radiation
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
- C23C14/06—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the coating material
- C23C14/08—Oxides
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
- C23C14/22—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the process of coating
- C23C14/34—Sputtering
- C23C14/35—Sputtering by application of a magnetic field, e.g. magnetron sputtering
- C23C14/352—Sputtering by application of a magnetic field, e.g. magnetron sputtering using more than one target
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
- C23C14/22—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the process of coating
- C23C14/54—Controlling or regulating the coating process
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
- C23C14/58—After-treatment
- C23C14/5806—Thermal treatment
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N52/00—Hall-effect devices
- H10N52/01—Manufacture or treatment
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N52/00—Hall-effect devices
- H10N52/80—Constructional details
- H10N52/85—Magnetic active materials
Abstract
The invention discloses a high coercivity hard magnetic oxide semiconductor film with perpendicular magnetic anisotropy and a preparation method thereof, wherein a process for alternately preparing a gradient film by multiple targets is adopted, and NiFeO4 and NiCo2O4 targets are used for alternately sputtering to prepare a NiCo2-xFexO4-NiCo2O4 gradient film. Experimental results show that the obtained film has coercive force as high as 1T and good electric conductivity, and abnormal Hall resistivity reaches 52.5 mu omega cm. The preparation method has the advantages of simplicity and lower cost, and provides new possibility for the research and development of the magnetic memory device. The method has important application potential for realizing the magnetic memory device with high density, high speed and low power consumption, and is beneficial to promoting the development and application of the magnetic memory technology.
Description
Technical Field
The invention belongs to the field of hard magnetic oxide film materials, and particularly relates to a high-coercivity hard magnetic oxide semiconductor film with perpendicular magnetic anisotropy and a preparation method thereof.
Background
Both the field of magnetic storage and the field of magnetic sensitivity place a high demand on hard magnetic materials with perpendicular magnetic anisotropy. Magnetic memory devices, such as hard disk drives and Magnetic Random Access Memories (MRAM), require high coercivity hard magnetic materials to achieve stable magnetic memory states, while the magnetic sensor field, especially the new generation of perpendicular TMR structures, requires highly stable perpendicular pinning layers, which requires the development of advanced perpendicular hard magnetic materials. However, conventional perpendicular magnetic anisotropic hard magnetic materials, such as cobalt alloys and iron cobalt boron, have some limitations, such as high cost, complex manufacturing processes, and high magnetic exchange coupling fields. Compared with a metal hard magnetic material, the oxide magnetic material has the advantages of high spin polarization rate, high impedance, capability of forming a better epitaxial structure with the MgO tunneling layer, theoretical high magnetic resistance and the like. Based on composition and strain regulation, the coercivity of the oxide magnetic material can be designed more conveniently to meet the requirements of different applications.
However, current oxide hard magnetic materials still have certain limitations in terms of coercivity and conductivity. Conventional oxide hard magnetic materials tend to have a lower coercivity and higher resistivity, which limits their use in the field of high density magnetic storage.
Therefore, there is an urgent need for a method for producing an oxide hard magnetic material capable of improving coercive force and conductivity. Improving the coercivity of oxide hard magnetic materials, particularly in the vertical direction, can significantly improve the performance and stability of the magnetic memory device. In addition, the conductivity of the oxide hard magnetic material is improved, so that the oxide hard magnetic material has lower resistivity, the power consumption of the magnetic memory device can be reduced, and the data reading and writing speed can be improved.
Therefore, the research and development of a method for preparing the oxide hard magnetic material with perpendicular magnetic anisotropy, high coercivity and conductivity has important scientific and application values.
Disclosure of Invention
This section is intended to outline some aspects of embodiments of the invention and to briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section as well as in the description summary and in the title of the application, to avoid obscuring the purpose of this section, the description summary and the title of the invention, which should not be used to limit the scope of the invention.
The present invention has been made in view of the above and/or problems occurring in the prior art.
It is therefore an object of the present invention to overcome the deficiencies in the prior art and to provide a high coercivity hard magnetic oxide semiconductor thin film having perpendicular magnetic anisotropy.
In order to solve the technical problems, the invention provides the following technical scheme: a high coercivity hard magnetic oxide semiconductor thin film having perpendicular magnetic anisotropy, comprising,
a substrate MgAl2O4 (101), a seed layer NiCo2O4 (102) and a film gradient layer NiCo2-xFexO4 (103);
the value of the doping quantity x of Fe of the NiCo2-xFexO4 gradually transits from the minimum value xmin to the maximum value xmax along with the thickness of the film from the substrate to the surface, the value range of xmin is 0-0.1, and the value range of xmax is 0.5-1;
the crystal orientation of the film is (001), and MgAl2O4 (001) single crystal is taken as a substrate.
As a preferred embodiment of the film according to the invention, wherein: when the Fe doping amount x=0, the film shows the lowest coercive force, weak perpendicular magnetic anisotropy and optimal conductivity, and the coercive force is generally not higher than 100Gs;
with the increase of xmax, the saturation magnetization and the coercivity of the film are gradually increased, and the coercivity exceeds 10000Gs at the proper thickness when xmax=1; the rectangular ratio of the film is always higher than 100%;
when xmax=xmin=1, i.e., there is no gradient in the thin film, the conductivity of the thin film is poor and the coercive force is lower than that of the gradient thin film.
It is still another object of the present invention to overcome the disadvantages of the prior art and to provide a method for preparing a high coercivity hard magnetic oxide semiconductor thin film having perpendicular magnetic anisotropy, comprising,
preparing targets of NiFe2O4 and NiCo2O4 by a standard ceramic sintering process;
depositing a film on a MgAl2O4 (001) single crystal substrate by adopting a NiCo2O4/NiFe2O4 target alternately by a pulse laser deposition or magnetron sputtering method, and controlling the thickness of the film by pulse/sputtering time;
and after the film is deposited, annealing in situ for 30-60 min to make the components more uniform, and cooling.
As a preferred embodiment of the preparation process according to the invention, there is provided: the MgAl2O4 (001) monocrystal substrate alternately adopts NiCo2O4/NiFe2O4 target material to deposit film, which comprises,
firstly, depositing a final film layer by adopting a NiCo2O4 target material, switching to a NiFe2O4 target material after a certain thickness, and detecting or calculating according to the thickness;
then switching to NiCo2O4 target material, controlling the component gradient change of Co and Fe in the film, and gradually transiting the doping amount of Fe from 0 to xmax.
As a preferred embodiment of the preparation process according to the invention, there is provided: the relative content of Fe and Co in the film is controlled by adjusting the proportion of NiCo2-xFexO4, and the component distribution from Co to Fe is gradually transited.
As a preferred embodiment of the preparation process according to the invention, there is provided: in the process of pulse laser deposition or magnetron sputtering, the component uniformity and crystallization quality of the film are optimized by adjusting the pulse/sputtering energy and frequency, and the proper temperature of the target and the angle of the substrate.
As a preferred embodiment of the preparation process according to the invention, there is provided: in the pulse laser deposition or magnetron sputtering process, the oxidation degree and lattice defects of the film are controlled by controlling the atmospheric oxygen pressure;
the oxygen pressure is 1 Pa-20 Pa.
As a preferred embodiment of the preparation process according to the invention, there is provided: the in-situ annealing is carried out for 30-60 min, the temperature is 350-500 ℃, and the oxygen pressure is 1 Pa-20 Pa.
As a preferred embodiment of the preparation process according to the invention, there is provided: in addition to the alternate sputter growth of the NiCo2O4/NiFe2O4 targets, direct preparation of the NiCoFeO4/NiCo2O4 targets, for example, achieves a specific gradient or ratio.
As a preferred embodiment of the preparation process according to the invention, there is provided: the method also comprises the step of realizing the stress regulation and control of the film by changing the components, the surface state and the structure of the substrate MgAl2O4, thereby realizing the optimization of coercive force and conductivity.
The invention has the beneficial effects that:
(1) The invention provides a preparation method of a high coercivity hard magnetic oxide semiconductor film with perpendicular magnetic anisotropy, which can overcome the limitations of the traditional oxide hard magnetic material, adopts NiFeO by adopting a preparation process of multi-target alternate pulse laser deposition or radio frequency magnetron sputtering 4 And NiCo 2 O 4 Target material, preparing NiCoFeO 4 -NiCo 2 O 4 Gradient film, the film obtained has coercive force as high as 1T, excellent conductivity, abnormal Hall resistivity as high as 52.5 mu omega cm.
(2) The preparation method has important application potential in the field of magnetic storage, and can provide new possibility for research and development of magnetic storage devices with high density, high speed and low power consumption; meanwhile, the method has the advantage of low material preparation cost, and is beneficial to realizing large-scale preparation and industrial production.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed in the description of the embodiments will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art. Wherein:
FIG. 1 is a block diagram of a NiCo2-xFexO4 gradient film provided in the examples;
FIG. 2 is an X-ray diffraction pattern of a NiCo2-xFexO4 gradient film provided in the examples;
FIG. 3 is an X-ray reciprocal space diffraction pattern of a NiCo2-xFexO4 gradient film provided in the examples;
FIG. 4 is an anomalous Hall curve of a 35nm NiCo2-xFexO4 gradient film and a pure NiCo2O4 film provided in the examples;
FIG. 5 is a flow chart of the preparation of a NiCo2-xFexO4 gradient film provided in the examples.
Detailed Description
In order that the above-recited objects, features and advantages of the present invention will become more apparent, a more particular description of the invention will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, but the present invention may be practiced in other ways other than those described herein, and persons skilled in the art will readily appreciate that the present invention is not limited to the specific embodiments disclosed below.
Further, reference herein to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic can be included in at least one implementation of the invention. The appearances of the phrase "in one embodiment" in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments.
As shown in FIG. 1, the invention provides a NiCo2-xFexO4 gradient film, which comprises a substrate MgAl2O4101, a seed layer NiCo2O4102 and a film gradient layer NiCo2-xFexO4103.
Wherein the seed layer 102 is located over the substrate 101; the seed layer 102 is mainly used for improving epitaxial matching, so that crystallization quality is improved; specifically, it is a single crystal thin film layer of NiCo2O4 having a thickness of 2 to 10nm and a (001) orientation;
the thin film gradient layer 103 is located above the seed layer 102, and can obtain better crystallization quality based on seed layer growth.
As shown in fig. 5, a method for preparing a perpendicular magnetic anisotropic hard magnetic oxide semiconductor film is provided, which includes steps 501 to 503:
step 501, a substrate layer is provided.
The substrate layer adopted by the invention is a MgAl2O4 substrate commonly used in commercial microwave devices, the MgAl2O4 substrate is a (001) -oriented monocrystalline MgAl2O4 substrate, the size of the substrate is 1x1cm, and the thickness of the substrate is 500 micrometers. After selecting the substrate, immersing the MgAl2O4 substrate into alcohol, carrying out vibration cleaning for 3-5 min by using ultrasonic cleaning equipment, and immediately placing the cleaned MgAl2O4 substrate on a base station of a deposition cavity of a magnetron sputtering system after drying by using nitrogen.
At step 502, a NiCo2O4 seed layer is formed on the substrate layer.
The NiCo2O4 seed layer can be prepared by a magnetron sputtering method. Preferably, the thickness of the seed layer is 2-10 nm.
And step 503, forming a gradient film layer on the seed layer.
Depositing a film on a MgAl2O4 (001) single crystal substrate by adopting a NiCo2O4/NiFe2O4 target alternately by a pulse laser deposition or magnetron sputtering method, and controlling the thickness of the film by pulse/sputtering time;
firstly, depositing a final film layer by adopting a NiCo2O4 target material, switching to the NiFe2O4 target material after a certain thickness, switching to the NiCo2O4 target material according to the thickness detection or calculation result, and controlling the component gradient change of Co and Fe in the film, wherein the doping amount of Fe gradually transits from 0 to xmax.
The thickness of the gradient film layer is 10-30 nm, the maximum value xmax of the Fe doping amount x of the film gradient layer NiCo2-xFexO4 is generally not higher than 1, the conductivity of the film is rapidly reduced when the Fe doping amount x is higher than 1, and the minimum value xmin of the doping amount x is generally not lower than 0.1.
The seed layer and the film gradient layer are sequentially prepared by adopting a radio frequency magnetron sputtering method:
before sputtering each layer of film, preparing the required ceramic target material of each layer by adopting a solid phase sintering method. The ceramic target material for growing the ferrimagnetic free layer and the ferrimagnetic reference layer NiCo2O4 film by using the radio frequency magnetron sputtering method is prepared from NiO powder and Co2O3 powder with the purity grade of 4N;
the ceramic target for growing the MgAl2O4 film of the tunneling layer is prepared from MgO powder with the purity grade of 4N and Al2O3 powder;
the preparation steps of the ceramic target material are as follows: mixing powder according to chemical proportion, adding binder, shaping in grinding tool, pressing into sheet by press, and sintering to obtain ceramic target. When the ceramic target is sintered, the sintering temperature is 100-200 ℃ lower than the phase forming temperature of each system.
The prepared ceramic target is installed in a magnetron sputtering system after being ground and polished, the distance between the ceramic target and a substrate is adjusted to be 40mm, and 1:1 argon/oxygen (Ar/O) is introduced 2 ) And (3) pre-sputtering the mixed gas for 10-12 hours in a room temperature environment with the air pressure regulated to 0.1-20 Pa, and removing impurities on the surface of the target material.
The deposition cavity of the magnetron sputtering system is pumped to a high vacuum state by a multistage pumping system formed by combining a mechanical pump and a molecular pump, so that the vacuum degree in the cavity is not less than 10 -6 mTorr to ensure clean growth environment; raising the temperature of the substrate of the deposition cavity to 350-500 ℃ so as to keep the substrate layer at the temperature of 350-500 ℃ for 10min; and finally, slowly introducing mixed gas of argon and oxygen with the volume ratio of 1:1 into the deposition cavity, and adjusting a mass flowmeter to ensure that the growth air pressure required in the deposition cavity is 100mTorr.
After the air pressure in the deposition cavity is stable, adjusting the growth time, and sequentially realizing the growth of the ferrimagnetic free layer and the tunneling layer on the substrate; and regulating the growth air pressure in the deposition cavity to be 200mTorr, and growing the ferrimagnetic reference layer.
In the embodiment of the invention, during sputtering, the growth thickness of each layer of film is not more than 100nm, the consumption of sputtering targets for each growth is small, and the nanoscale film meets the requirement of miniaturization and integration. The preparation method is an industrial mass production method by radio frequency magnetron sputtering, has good process compatibility at the growth temperature of 350-500 ℃, and meets the requirements of the current industrial mass production.
In the embodiment of the invention, the oxidation degree and lattice defects of the film can be controlled by controlling the oxygen pressure of the atmosphere; typically, the oxygen pressure is between 1Pa and 20Pa, and the higher the pressure, the greater the film coercivity. The annealing can be performed for half an hour under the oxygen pressure of 1Pa to 20Pa within the range of 350 ℃ to 500 ℃ so as to promote the optimization of the thin film crystal structure and the improvement of the magnetic property, and the higher the oxygen pressure is, the higher the coercive force is, the higher the temperature is, and the higher the resistivity is.
In the embodiment of the invention, besides adopting the NiCo2O4/NiFe2O4 target material for alternate sputtering growth, the NiCoFeO4/NiCo2O4 target material can also be directly prepared to realize specific gradient or proportion; the stress regulation and control of the film can be realized by changing the components, the surface state and the structure of the substrate MgAl2O4, so that the coercivity and the conductivity can be optimized, and the requirements of different application fields can be met.
The material can realize the custom coercivity from 100Gs to more than 10000Gs, and does not need a magnetic annealing process, and only needs the stress regulation of the substrate.
Example 1
The preparation method of the high coercivity hard magnetic oxide semiconductor film with perpendicular magnetic anisotropy comprises the following process steps:
step 1: the targets of NiFe2O4 and NiCo2O4 are prepared through a standard ceramic sintering process, and the substrate is cleaned, placed in a cavity, vacuumized and heated to be ready for work. After the vacuum degree was reached, an oxygen atmosphere of 13Pa was maintained, and the substrate was heated to 350 ℃.
The preparation process of the NiFe2O4 target material is as follows:
mixing Ni2O3 with purity of over 99.9 percent with Fe2O3 powder according to the proportion of 1:2, ball milling, granulating, pressing into a target material under 15kPa pressure, and sintering into porcelain at 1000 ℃.
The preparation process of the NiCo2O4 target material is as follows:
mixing Ni2O3 with purity of over 99.9 percent and Co2O3 powder according to the proportion of 1:2, ball milling, granulating, pressing into a target material under 15kPa pressure, and sintering into porcelain at 1000 ℃.
Step 2: depositing a film on a MgAl2O4 (001) single crystal substrate by adopting a NiCo2O4/NiFe2O4 target alternately by a pulse laser deposition or magnetron sputtering method, and controlling the thickness of the film by pulse/sputtering time;
specifically, the energy density of pulsed laser deposition is about 2J/cm 2 The speed is 120 pulse/nm, the power of magnetron sputtering is 50w, and the speed is 50 nm/hour;
firstly, depositing an initial film layer by adopting a NiCo2O4 target material, switching to a NiFe2O4 target material after a first thickness, and switching to a NiCo2O4 target material according to the result of thickness detection or calculation, wherein the gradient change of the components of Co and Fe in the film is controlled, and the doping amount of Fe is gradually transited from 0 to xmax; the first thickness is usually 5nm, and the total thickness of the thin film is preferably 22 to 30nm as a growth seed layer.
Step 3: after the film deposition is finished, in-situ annealing is carried out for 30 minutes at 350-500 ℃ to ensure that the components are more uniform, and then cooling is carried out to room temperature.
Specifically, in step 1, the relative content of Fe and Co in the film is controlled by adjusting the proportion of NiCo2-xFexO4, the component distribution from Co to Fe is gradually transited, and the component gradient is realized by continuously increasing the thickness of the NiCoFeO4 layer and improving the components by additional annealing.
In one embodiment, the maximum doping amount x=1 of Fe is as follows: niCo2O4 (3 nm) →NiCoFeO4 (1 nm) →NiCo2O4 (1 nm) →NiCoFeO4 (2 nm) →NiCo2O4 (1 nm) →NiCoFeO4 (3 nm) →NiCo2O4 (1 nm) →NiCoFeO4 (4 nm) →NiCo2O4 (1 nm) →NiCo2O4 (5 nm).
In the process of pulse laser deposition or magnetron sputtering in the step 2, the component uniformity and crystallization quality of the thin film can be optimized by adjusting the pulse/sputtering energy and frequency, as well as the proper temperature of the target and the angle of the substrate.
Fig. 2 shows the X-ray diffraction results of the above thin film structure, and shows that the single orientation thereof is demonstrated by the presence of only a thin film diffraction peak of (004) at about 43 degrees and a diffraction peak of the substrate at about 44 degrees.
Fig. 3 shows the X-ray reciprocal space diffraction result of the above film structure, and it can be seen that the diffraction peak 104 of the film is collinear with the diffraction peak 105 of the substrate, and exhibits a coherent growth mode. This is a precondition for high coercivity.
The maximum value xmax of the Fe doping amount x of the film gradient layer NiCo2-xFexO4 is generally not higher than 1, the conductivity of the film is sharply reduced when the Fe doping amount x is higher than 1, and the coercive force is generally lower than 2000Gs when the Fe doping amount x is lower than 0.5; the Fe doping level x minimum is typically 0 or not higher than 0.1 to ensure good lattice matching and transition.
The abnormal hall resistance of the gradient film was measured by patterning hall bar, as shown in fig. 4, and in the example, the NiCo2O4 seed layer had a thickness of 5nm and the gradient layer had a thickness of 22nm, and the obtained film had an abnormal hall resistance of 15 Ω and an abnormal hall resistivity of 52.5 μΩ·cm, which is far higher than that of the metal conforming multilayer film material (usually not higher than 10) including CoFeB multilayer film. Compared with the NiCo2O4 pure film with the same thickness, the film has great improvement. The NiCoFeO4 pure film is too high in resistance to measure abnormal hall signals.
The present invention aims to provide a hard magnetic oxide semiconductor thin film having perpendicular magnetic anisotropy, high coercive force and certain conductivity. On one hand, the preparation method needs good epitaxial matching relation between the thin film and the substrate so as to realize a high-crystallization multilayer film material; on the other hand, a high coercive force structure needs to be realized by controlling the film composition. The growth process and structural design of high-crystalline high-quality multilayer films are of paramount importance. In addition, the conventional ferromagnetic free layer material can generate ferromagnetic resonance phenomenon in the GHz frequency band, so that the response speed of the device is limited, and the response speed can further influence the working frequency band of the sensor.
Therefore, research on new material structures of oxide semiconductor thin films with high spin polarizability, high magnetoresistance and high response speed is needed to meet the growing demand for developing magneto-sensitive elements.
The invention provides a high-coercivity hard magnetic oxide semiconductor film with perpendicular magnetic anisotropy, which comprises the material composition of NiCo2-xFexO4, wherein the value of Fe doping amount x gradually transits from a minimum value xmin to a maximum value xmax along with the thickness of the film from a substrate to a surface. The crystal orientation of the film is (001), and MgAl2O4 (001) single crystal is taken as a substrate. When the Fe doping amount x=0, the thin film exhibits the lowest coercive force, weak perpendicular magnetic anisotropy, and optimal conductivity, and the coercive force is generally not higher than 100Gs. As xmax increases, the saturation magnetization and coercivity of the film gradually increase, and the coercivity may exceed 10000Gs at an appropriate thickness at xmax=1. The rectangular ratio of the film is always higher than 100%. When xmax=xmin=1, i.e., there is no gradient in the thin film, the conductivity of the thin film is poor and the coercive force is lower than that of the gradient thin film.
In summary, the invention provides a preparation method of a high coercivity hard magnetic oxide semiconductor film with perpendicular magnetic anisotropy, which can overcome the limitations of the traditional oxide hard magnetic material, and adopts NiFeO by adopting a preparation process of multi-target alternating pulse laser deposition or radio frequency magnetron sputtering 4 And NiCo 2 O 4 Target material, preparing NiCoFeO 4 -NiCo 2 O 4 Gradient film, the film obtained has coercive force as high as 1T, excellent conductivity, abnormal Hall resistivity as high as 52.5 mu omega cm.
It should be noted that the above embodiments are only for illustrating the technical solution of the present invention and not for limiting the same, and although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solution of the present invention may be modified or substituted without departing from the spirit and scope of the technical solution of the present invention, and it should be covered in the scope of the present invention.
Claims (10)
1. A high coercivity hard magnetic oxide semiconductor film with perpendicular magnetic anisotropy is characterized in that: comprising the steps of (a) a step of,
a substrate MgAl2O4 (101), a seed layer NiCo2O4 (102) and a film gradient layer NiCo2-xFexO4 (103);
the value of the doping quantity x of Fe of the NiCo2-xFexO4 gradually transits from the minimum value xmin to the maximum value xmax along with the thickness of the film from the substrate to the surface, the value range of xmin is 0-0.1, and the value range of xmax is 0.5-1;
the crystal orientation of the film is (001), and MgAl2O4 (001) single crystal is taken as a substrate.
2. The film of claim 1, wherein: when the doping amount of Fe is x=0, the thin film exhibits the lowest coercive force, weak perpendicular magnetic anisotropy and optimal conductivity, and the coercive force is generally not higher than 100Gs;
with the increase of xmax, the saturation magnetization and the coercivity of the film are gradually increased, and the coercivity exceeds 10000Gs at the proper thickness when xmax=1; the rectangular ratio of the film is always higher than 100%;
when xmax=xmin=1, i.e., there is no gradient in the thin film, the conductivity of the thin film is poor and the coercive force is lower than that of the gradient thin film.
3. A method for producing a film according to claim 1 or 2, characterized in that: comprising the steps of (a) a step of,
preparing targets of NiFe2O4 and NiCo2O4 by a standard ceramic sintering process;
depositing a film on a MgAl2O4 (001) single crystal substrate by adopting a NiCo2O4/NiFe2O4 target alternately by a pulse laser deposition or magnetron sputtering method, and controlling the thickness of the film by pulse/sputtering time;
and after the film is deposited, annealing in situ for 30-60 min to make the components more uniform, and cooling.
4. A method of producing a film according to claim 3, wherein: the MgAl2O4 (001) monocrystal substrate alternately adopts NiCo2O4/NiFe2O4 target material to deposit film, which comprises,
firstly, depositing a final film layer by adopting a NiCo2O4 target material, switching to a NiFe2O4 target material after a certain thickness, and detecting or calculating according to the thickness;
then switching to NiCo2O4 target material, controlling the component gradient change of Co and Fe in the film, and gradually transiting the doping amount of Fe from 0 to xmax.
5. A method of producing a film according to claim 3, wherein: the relative content of Fe and Co in the film is controlled by adjusting the proportion of NiCo2-xFexO4, and the component distribution from Co to Fe is gradually transited.
6. A method of producing a film according to claim 3, wherein: in the process of pulse laser deposition or magnetron sputtering, the component uniformity and crystallization quality of the film are optimized by adjusting the pulse/sputtering energy and frequency, and the proper temperature of the target and the angle of the substrate.
7. A method of producing a film according to claim 3, wherein: in the pulse laser deposition or magnetron sputtering process, the oxidation degree and lattice defects of the film are controlled by controlling the atmospheric oxygen pressure;
the oxygen pressure is 1 Pa-20 Pa.
8. A method of producing a film according to claim 3, wherein: the in-situ annealing is carried out for 30-60 min, the temperature is 350-500 ℃, and the oxygen pressure is 1 Pa-20 Pa.
9. A method of producing a film according to claim 3, wherein: the method also comprises the step of directly preparing the NiCoFeO4/NiCo2O4 target material to realize specific gradient or proportioning.
10. A method of producing a film according to claim 3, wherein: the method also comprises the step of realizing the stress regulation and control of the film by changing the components, the surface state and the structure of the substrate MgAl2O4, thereby realizing the optimization of coercive force and conductivity.
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