Nitrogen-doped ferrite thin film and preparation method and application thereof

Abstract

The present application relates to a kind of nitrogen-doped ferrite film and its preparation method and application.The chemical formula of nitrogen-doped ferrite film is: MFe2O 4‑x N y , 0<x≤2, 0<y≤1.5 and 0<2x-3y≤1;Or MFeO 3‑x N y , 0<x≤2, 0<y≤1.5 and 0<2x-3y≤2;Or M3Fe5O 12‑x N y , 0<x≤6, 0<y≤4 and 0<2x-3y≤5;Or MFe 12 O 19‑x N y , 0

Description

Technical Field

[0001] The present invention relates to the field of magnetic materials, and particularly to a nitrogen-doped ferrite thin film, a preparation method thereof, and an application thereof. Background Art

[0002] Due to their high chemical stability, high thermal stability, low loss, excellent static magnetic and high-frequency magnetic properties, ferrites have important applications in the fields of magnetic storage devices, magnetic sensors, high-frequency communication devices, magneto-optical devices, spintronic devices, etc. In addition, due to their advantages such as narrow bandgap (in the visible light absorption range), semiconductor characteristics, low cost, and high chemical stability, ferrites have also received increasing attention in the energy fields such as photocatalytic water splitting and solar energy collection.

[0003] In traditional technologies, the regulation of the magnetic, semiconductor, optical and other physical properties of ferrites is mainly achieved through the doping and substitution of metal cations. With the deepening of research, the doping of metal cations has become increasingly complex. Metal cation doping often has an obvious regulatory effect on the conduction band electron structure, but the regulatory effect on the valence band electron structure is very limited. Therefore, solely focusing on metal cation doping is becoming increasingly limited for further improving the performance of ferrites. Summary of the Invention

[0004] Based on this, in view of the above problems, it is necessary to provide a nitrogen-doped ferrite thin film, a preparation method thereof, and an application thereof; the nitrogen-doped ferrite thin film has high crystallization quality, excellent single crystal characteristics, room temperature saturation magnetization intensity, and semiconductor properties, and can be widely applied to electronic devices.

[0005] The chemical formula of a nitrogen-doped ferrite thin film is:

[0006] MFe2O 4-x N y , where 0 < x ≤ 2, 0 < y ≤ 1.5, and 0 < 2x - 3y ≤ 1;

[0007] Or, MFeO 3-x N y , where 0 < x ≤ 2, 0 < y ≤ 1.5, and 0 < 2x - 3y ≤ 2;

[0008] Or, M3Fe5O 12-x N y , where 0 < x ≤ 6, 0 < y ≤ 4, and 0 < 2x - 3y ≤ 5;

[0009] Or, MFe 12 O 19-x N y , where 0 < x ≤ 10, 0 < y ≤ 7, and 0 < 2x - 3y ≤ 12;

[0010] M is selected from at least one of monovalent, divalent, and trivalent metal elements, or an alloy composed of at least two of monovalent, divalent, and trivalent metal elements.

[0011] In one embodiment, the monovalent metal element is selected from lithium;

[0012] And / or, the divalent metal element is selected from at least one of magnesium, calcium, strontium, barium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, and zinc;

[0013] And / or, the trivalent metal element is selected from at least one of yttrium, bismuth, or lanthanides.

[0014] In one embodiment, the thickness of the nitrogen-doped ferrite film is 1 nm-1 μm.

[0015] The nitrogen-doped ferrite thin film of this invention, through nitrogen ion doping and substitution of some oxygen atoms in the ferrite lattice, while simultaneously introducing certain vacancies, can effectively control the 2p orbital structure at the valence band top of the ferrite lattice, thereby creating a new control mechanism for the electrical, magnetic, and optical properties of ferrite. Compared to metal cation-doped ferrite thin films, nitrogen-doped ferrite thin films have higher crystal quality and better single-crystal characteristics. This allows nitrogen-doped ferrite thin films to maintain the original magnetic properties of ferrite thin films while increasing the imaginary part of the near-infrared dielectric constant, improving the absorption capacity of the film in the visible and near-infrared bands, and giving nitrogen-doped ferrite thin films excellent optoelectronic properties.

[0016] A method for preparing a nitrogen-doped ferrite thin film as described above includes the following steps:

[0017] We provide ferrite sputtering targets and single-crystal substrates;

[0018] Under vacuum conditions, the temperature of the single crystal substrate is controlled, and thin film is grown on the single crystal substrate in a nitrogen-containing atmosphere. After cooling, a nitrogen-doped ferrite thin film is obtained.

[0019] In one embodiment, the ferrite target is selected from spinel ferrite, perovskite ferrite, garnet ferrite or hexagonal ferrite.

[0020] In one embodiment, the thickness of the ferrite target is less than or equal to 3 mm.

[0021] In one embodiment, the single-crystal substrate is selected from SrTiO3, LaAlO3, (La,Sr)(Al,Ta)O3, KTaO3, MgAl2O4, Al2O3, and Gd3Ga5O. 12 Y3Al5O 12At least one of Si, SiC, GaN, and GaAs.

[0022] In one embodiment, the volume fraction of nitrogen in the nitrogen-containing gas is greater than or equal to 0.1%.

[0023] In one embodiment, the background vacuum level is less than or equal to 10 before thin film growth begins. -5 Torr;

[0024] And / or, the pressure of nitrogen-containing gas during film growth is 0.1 Pa - 200 Pa;

[0025] And / or, in the step of adjusting the temperature of the single crystal substrate, the temperature of the single crystal substrate is made to be greater than 25°C.

[0026] An electronic device made of nitrogen-doped ferrite thin film as described above.

[0027] In the method for preparing nitrogen-doped ferrite thin films according to the present invention, ferrite is used as the target material, and nitrogen gas is converted into N2 in a nitrogen-containing atmosphere. 3- This method enables nitrogen atoms to be effectively incorporated into the ferrite lattice, thereby preparing highly crystalline nitrogen-doped ferrite thin films. This preparation method does not rely on the oxygen-containing atmosphere required for traditional ferrite thin film preparation and is more compatible with semiconductor processes, thus providing a practical preparation method for integrating nitrogen-doped ferrite thin films with semiconductor devices.

[0028] Therefore, electronic devices based on nitrogen-doped ferrite thin films provided by this invention can be widely used in fields such as magneto-optics and photocatalysis, and can help promote the development of new integrated microwave, nanomagnetic storage devices, magnetic sensors, spintronic devices and other technologies. Attached Figure Description

[0029] Figure 1 This is a schematic diagram illustrating the principle of preparing nitrogen-doped ferrite thin films by magnetron sputtering in one embodiment of the present invention;

[0030] Figure 2 This is a comparison image of the nitrogen-doped lithium ferrite film prepared in Example 1 of the present invention and the lithium ferrite film prepared in Comparative Example 1.

[0031] Figure 3 The image shows the crystal structure of the nitrogen-doped lithium ferrite film prepared in Example 1 of this invention, as well as the X-ray diffraction patterns of the nitrogen-doped lithium ferrite film prepared in Example 1 and the lithium ferrite film prepared in Comparative Example 1.

[0032] Figure 4 This is a comparison diagram of the magnetic properties of the nitrogen-doped lithium ferrite film prepared in Example 1 of the present invention and the lithium ferrite film prepared in Comparative Example 1.

[0033] Figure 5 Dielectric constant comparison diagram of the nitrogen-doped lithium ferrite thin film prepared in Example 1 of the present invention and the lithium ferrite thin film prepared in Comparative Example 1 in the visible and near-infrared bands.

[0034] Among them, 10, ferrite target; 20, ferrite atomic clusters; 30, nitrogen-doped ferrite thin film; 40, single crystal substrate; a, nitrogen-doped lithium ferrite thin film prepared in Example 1; b, lithium ferrite thin film prepared in Comparative Example 1. Detailed implementation manners

[0035] For the convenience of understanding the present invention, the present invention will be described in more detail below. However, it should be understood that the present invention can be implemented in many different forms and is not limited to the embodiments or examples described herein. On the contrary, the purpose of providing these embodiments or examples is to make the understanding of the disclosure content of the present invention more thorough and comprehensive.

[0036] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments or examples and are not intended to limit the present invention.

[0037] The present invention provides a nitrogen-doped ferrite thin film, and the chemical formula of the nitrogen-doped ferrite thin film is:

[0038] MFe2O 4-x N y , where 0 < x ≤ 2, 0 < y ≤ 1.5, and 0 < 2x - 3y ≤ 1;

[0039] Or, MFeO 3-x N y , where 0 < x ≤ 2, 0 < y ≤ 1.5, and 0 < 2x - 3y ≤ 2;

[0040] Or, M3Fe5O 12-x N y , where 0 < x ≤ 6, 0 < y ≤ 4, and 0 < 2x - 3y ≤ 5;

[0041] Or, MFe 12 O 19-x N[[ID=​​​​​

[0043] By using nitrogen ion doping to replace some oxygen atoms in the ferrite lattice and introducing certain vacancies simultaneously, the 2p orbital structure at the top of the valence band in the ferrite lattice can be effectively regulated, thereby generating a new regulation mechanism for the electrical, magnetic, optical and other properties of the ferrite.

[0044] Compared with the metal cation-doped ferrite thin film, the nitrogen-doped ferrite thin film has high crystallization quality and good single crystal characteristics, enabling the nitrogen-doped ferrite thin film to increase the imaginary part of the dielectric constant in the near-infrared band and improve the absorption capacity of the thin film in the visible light near-infrared band while maintaining the magnetic properties of the original ferrite thin film, endowing the nitrogen-doped ferrite thin film with excellent optoelectronic properties.

[0045] Based on the different crystal phases of the ferrite matrix, the nitrogen-doped ferrite thin film has different crystal structures.

[0046] Specifically, when the ferrite is selected from spinel ferrite (MFe2O4), the chemical formula of the nitrogen-doped ferrite thin film is MFe2O 4-x N y , where 0 < x ≤ 2, 0 < y ≤ 1.5, and 0 < 2x - 3y ≤ 1, and M is selected from monovalent metal elements, divalent metal elements or an alloy composed of at least two elements of monovalent metal elements and divalent metal elements, preferably lithium, magnesium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, or an alloy composed of at least two elements of lithium, magnesium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc.

[0047] More preferably, it is (LiFe) 0.5 Fe2O 4-x N y , where 0 < x ≤ 2, 0 < y ≤ 1.5 and 0 < 2x - 3y ≤ 1.

[0048] When the ferrite is selected from perovskite ferrite (MFeO3), the chemical formula of the nitrogen-doped ferrite thin film is MFeO 3-x N y , where 0 < x ≤ 2, 0 < y ≤ 1.5, and 0 < 2x - 3y ≤ 2, and M is selected from divalent metal elements, trivalent metal elements or an alloy composed of at least two elements of divalent metal elements and trivalent metal elements, preferably calcium, strontium, barium, bismuth, lanthanide elements, or an alloy composed of at least two elements of calcium, strontium, barium, bismuth, lanthanide elements.

[0049] When the ferrite is selected from garnet ferrite (M3Fe5O 12 ), the chemical formula of the nitrogen-doped ferrite thin film is M3Fe5O 12-x N y, where \(0 < x \leq 6\), \(0 < y \leq 4\), and \(0 < 2x - 3y \leq 5\), \(M\) is selected from trivalent metal elements or alloys composed of at least two elements among trivalent metal elements, preferably yttrium, samarium, gadolinium, holmium, or alloys composed of at least two elements among yttrium, samarium, gadolinium, holmium.

[0050] When the ferrite is selected from hexagonal ferrites (\(MFe\) 12 O 19 ), the chemical formula of the nitrogen-doped ferrite thin film is \(MFe\) 12 O 19- x N y , where \(0 < x \leq 10\), \(0 < y \leq 7\), and \(0 < 2x - 3y \leq 12\), \(M\) is selected from divalent metal elements or alloys composed of at least two elements among divalent metal elements, preferably calcium, strontium, barium, or alloys composed of at least two elements among calcium, strontium, barium.

[0051] For applications in actual magnetic, spintronic, and photocatalytic devices, the thickness of the nitrogen-doped ferrite thin film is \(1\ nm - 1\ \mu m\), preferably \(10\ nm - 500\ nm\).

[0052] The present invention also provides a method for preparing a nitrogen-doped ferrite thin film, comprising the following steps:

[0053] S1, providing a ferrite target and a single crystal substrate;

[0054] S2, under vacuum conditions, regulating the temperature of the single crystal substrate, and performing thin film growth on the single crystal substrate in a nitrogen-containing atmosphere, and obtaining a nitrogen-doped ferrite thin film after cooling.

[0055] In step S1, the ferrite target is selected from spinel ferrites, perovskite ferrites, garnet ferrites, or hexagonal ferrites.

[0056] In one embodiment, the method for preparing the ferrite comprises the following steps: selecting initial raw materials such as carbonates and metal oxides for synthesizing the ferrite, mixing them according to a certain stoichiometric ratio, and then performing standard solid-phase reaction process steps such as wet ball milling, drying, calcination reaction, shaping, and sintering to prepare the ferrite target. In order to allow the magnetic induction lines of the magnetic target gun to pass through the ferrite smoothly and make the target easier to glow, it is preferred to thin the thickness of the ferrite target so that the thickness of the ferrite target is less than or equal to \(3\ mm\).

[0057] Considering the lattice matching characteristics of the ferrite target and its nitrogen-doped ferrite thin film with the single crystal substrate, the material of the single crystal substrate is selected from \(SrTiO_3\), \(LaAlO_3\), \((La,Sr)(Al,Ta)O_3\), \(KTaO_3\), \(MgAl_2O_4\), \(MgO\), \(Al_2O_3\), \(Gd_3Ga_5O\) 12Y3Al5O 12 It contains at least one of Si, SiC, GaN, and GaAs, preferably at least one of MgAl2O4 and MgO.

[0058] To prepare high-quality nitrogen-doped ferrite films, the single-crystal substrate is pre-cleaned and dried to remove potential surface contaminants.

[0059] In step S2, deposition growth is performed in a nitrogen-containing gas, which ensures that nitrogen ions are doped into the ferrite lattice, achieving effective nitriding. In the nitrogen-containing gas, the volume fraction of nitrogen is greater than or equal to 0.1%. Preferably, the volume fraction of nitrogen is greater than or equal to 1%, and more preferably, the volume fraction of nitrogen is greater than or equal to 10%.

[0060] Specifically, the nitrogen-containing gas is preferably a mixture of nitrogen and an inert gas, and more preferably a mixture of nitrogen and argon.

[0061] To obtain nitrogen-doped ferrite films with high crystallinity, the background vacuum level before film growth should be less than or equal to 10. -5 Torr; and / or, the pressure of nitrogen-containing gas during thin film growth is 0.1 Pa to 200 Pa; and / or, in the step of controlling the temperature of the single crystal substrate, the temperature of the single crystal substrate is greater than 25 °C.

[0062] Preferably, the pressure of the nitrogen-containing gas is 1 Pa to 200 Pa; the temperature of the single crystal substrate is greater than 25°C and less than or equal to 1000°C.

[0063] Further optimization involves using nitrogen-containing gas at a pressure of 5 Pa to 100 Pa and a single-crystal substrate at a temperature of 500°C to 800°C.

[0064] In one embodiment, the deposition method is preferably magnetron sputtering, and the principle of preparing nitrogen-doped ferrite thin films using magnetron sputtering is as follows: Figure 1 As shown, the specific operation includes: first, pre-sputtering the ferrite target 10 for 10-30 minutes, then heating the single crystal substrate 40 at a rate of 5℃ / min-25℃ / min and sputtering it, so that the ferrite atomic clusters 20 formed by the ferrite target 10 are deposited on the single crystal substrate 40, and the nitrogen converted from nitrogen is used. 3- Nitrogen-doped ferrite thin films are deposited and grown. The sputtering power of the RF power supply is 10W-500W.

[0065] Pre-sputtering can remove adsorbed gases on the surface of the ferrite target 10 and eliminate the adverse effects of initial sputtering instability on the growth of nitrogen-doped ferrite films 30.

[0066] To ensure a moderate ferrite sputtering rate, achieve efficient nitriding of the ferrite film while maintaining good density, improve the crystal quality of the nitrogen-doped ferrite film 30, and facilitate the acquisition of epitaxial films, the preferred sputtering power of the RF power supply is 20W-200W.

[0067] By controlling the deposition time, nitrogen-doped ferrite films 30 with thicknesses ranging from 1 nm to 1000 nm can be obtained. Furthermore, after the deposition of the nitrogen-doped ferrite film 30 is completed, the single-crystal substrate is cooled at a rate of 5 °C / min to 25 °C / min under the same atmosphere as the growth atmosphere. This effectively prevents the nitrogen-doped ferrite film 30 from being re-oxidized, thus solidifying nitrogen atoms within the lattice of the nitrogen-doped ferrite film 30.

[0068] It should be noted that the nitrogen-doped ferrite film obtained by the preparation method provided by the present invention can be used separately from a single crystal substrate, or it can be used as an integral film with the single crystal substrate, depending on different application requirements. The present invention does not limit this.

[0069] This preparation method involves depositing ferrite targets under nitrogen-containing gas, and converting nitrogen into N under certain conditions. 3- This method enables nitrogen atoms to be effectively incorporated into the ferrite lattice, thereby preparing highly crystalline nitrogen-doped ferrite thin films. This preparation method does not rely on the oxygen-containing atmosphere required for traditional ferrite thin film preparation and is more compatible with semiconductor processes, thus providing a practical preparation method for integrating nitrogen-doped ferrite thin films with semiconductor devices.

[0070] The present invention also provides an electronic device made of nitrogen-doped ferrite thin film.

[0071] Electronic devices based on nitrogen-doped ferrite thin films provided by this invention can be widely used in fields such as magneto-optics and photocatalysis, and can help promote the development of new integrated microwave, nanomagnetic storage devices, magnetic sensors, spintronic devices and other technologies.

[0072] The nitrogen-doped ferrite thin film, its preparation method, and its application will be further explained below through specific embodiments.

[0073] Example 1

[0074] Lithium ferrite (LiFe5O8) from spinel ferrite was selected as the target material. First, initial raw materials of LiCO3 (99.99% ultrapure) and Fe2O3 (99.99% ultrapure) in a molar ratio of 2:5 were prepared. Following standard solid-state reaction processes including wet ball milling, drying, calcination, molding, and sintering, a 2-inch ultrapure (99.99%) LiFe5O8 (LFO) magnetron sputtering target was prepared. The target thickness was then reduced to 1.5 mm, and the LFO target was loaded onto the target gun of the magnetron sputtering system. Simultaneously, MgAl2O4 was selected as the single-crystal substrate. The MgAl2O4 single-crystal substrate was ultrasonically cleaned for 5 minutes and dried with a nitrogen gun. Then, the MgAl2O4 single-crystal substrate was fixed on a heating stage.

[0075] The base vacuum of the sputtering chamber was evacuated to 10 using mechanical and molecular pumps. -8 Torr, the heating stage temperature was increased to 800℃ at a rate of 25℃ / min. The mass flow meter valves for N2 and Ar gases were adjusted to control the N2 gas volume fraction to 100%, and the vacuum valve was adjusted to maintain a chamber gas pressure of approximately 2.66 Pa. The sputtering power was set to 80W, and the LFO target was pre-sputtered for 30 minutes. Then, the heating stage baffle was opened to allow the nitrogen-doped lithium ferrite film to grow on the single-crystal substrate. After deposition, the single-crystal substrate was cooled at a rate of 25℃ / min under the same atmosphere as the growth atmosphere to obtain a nitrogen-doped lithium ferrite (LiFe) film with a thickness of approximately 30 nm. 0.5 Fe2O 4-x N y (where x = 0.5, y = 0.1).

[0076] Tests showed that the nitrogen-doped lithium ferrite film has good single-crystal properties, with a saturation magnetization of up to 230 emu / cc at room temperature.

[0077] Example 2

[0078] The only difference between Example 2 and Example 1 is that the single-crystal substrate is MgO, the heating stage temperature is 600℃, and a nitrogen-doped lithium ferrite (LiFe) film with a thickness of approximately 30nm is obtained. 0.5 Fe2O 4-x N y (where x = 0.5, y = 0.1).

[0079] Tests showed that the nitrogen-doped lithium ferrite film has good single-crystal properties, with a saturation magnetization of 165 emu / cc at room temperature.

[0080] Example 3

[0081] The only difference between Example 3 and Example 1 is that the sputtering pressure was maintained at 0.67 Pa during the sputtering process, resulting in a nitrogen-doped lithium ferrite (LiFe) film with a thickness of approximately 30 nm. 0.5 Fe2O 4-x N y (where x = 0.4, y = 0.08).

[0082] Tests showed that the nitrogen-doped lithium ferrite film exhibited epitaxial single-crystal properties, with a saturation magnetization of 190 emu / cc at room temperature.

[0083] Example 4

[0084] Bismuth ferrite (BiFeO3, BFO) from perovskite ferrite was selected as the target material, and SrTiO3 was selected as the single crystal substrate. The SrTiO3 single crystal substrate was ultrasonically cleaned for 10 minutes and dried with a nitrogen gun. Then, the SrTiO3 single crystal substrate was fixed on the heating stage.

[0085] The base vacuum of the sputtering chamber was evacuated to 10 using mechanical and molecular pumps. -4 Torr, the heating stage temperature was increased to 800℃ at a rate of 25℃ / min. The mass flow meter valves for N2 and Ar gases were adjusted to control the N2 gas volume fraction to 90%, and the vacuum valve was adjusted to maintain a chamber gas pressure of approximately 5 Pa. The sputtering power was set to 100W, and the BFO target was pre-sputtered for 30 minutes. Then, the heating stage baffle was opened to allow the nitrogen-doped bismuth ferrite film to deposit and grow on the single-crystal substrate. After deposition, the single-crystal substrate was cooled at 25℃ / min under the same atmosphere as the growth atmosphere to obtain a nitrogen-doped bismuth ferrite film (BiFeO) with a thickness of approximately 30 nm. 2.5 N 0.2 ).

[0086] Tests showed that the nitrogen-doped bismuth ferrite film has good single-crystal properties, with a saturation magnetization of 20 emu / cc at room temperature.

[0087] Example 5

[0088] Select yttrium ferrite (Y3Fe5O) from garnet ferrite. 12 YIG) as the target material, Gd3Ga5O 12 (GGG) was used as a single crystal substrate. The GGG single crystal substrate was ultrasonically cleaned for 10 minutes and dried with a nitrogen gun. Then the GGG single crystal substrate was fixed on the heating stage.

[0089] The base vacuum of the sputtering chamber was evacuated to 10 using mechanical and molecular pumps. -5Torr, the heating stage temperature was increased to 850℃ at a rate of 25℃ / min. The mass flow meter valves for N2 and Ar gases were adjusted to control the N2 gas volume fraction to 100%, and the vacuum valve was adjusted to maintain a chamber gas pressure of approximately 4.5 Pa. The sputtering power was set to 85W, and the YIG target was pre-sputtered for 30 minutes. Then, the heating stage baffle was opened to allow nitrogen-doped yttrium ferrite (Y3Fe5O3) thin films to deposit and grow on the single-crystal substrate. After deposition, the single-crystal substrate was cooled at a rate of 25℃ / min under the same atmosphere as the growth atmosphere to obtain a nitrogen-doped yttrium ferrite (Y3Fe5O3) thin film with a thickness of approximately 50 nm. 10 N).

[0090] Tests showed that the nitrogen-doped yttrium ferrite film has good single-crystal properties, with a saturation magnetization of 131 emu / cc at room temperature.

[0091] Example 6

[0092] Barium ferrite (BaFe) from hexagonal ferrites was selected. 12 O 19 Using c-Al2O3 as the target material and c-Al2O3 as the single crystal substrate, the c-Al2O3 single crystal substrate was ultrasonically cleaned for 10 minutes and dried with a nitrogen gun. Then, the c-Al2O3 single crystal substrate was fixed on the heating stage.

[0093] The base vacuum of the sputtering chamber was evacuated to 10 using mechanical and molecular pumps. -4 Torr increased the heating stage temperature to 600℃ at a rate of 25℃ / min. The N2 and Ar mass flow meter valves were adjusted to control the N2 gas volume fraction at 95%. The vacuum valve was adjusted to maintain a chamber gas pressure of approximately 3 Pa. The sputtering power supply was set to 100W for BaFe... 12 O 19 The target was pre-sputtered for 30 minutes, and then the heating stage baffle was turned on to allow the nitrogen-doped barium ferrite film to be deposited and grown on the single crystal substrate. After deposition, the single crystal substrate was cooled at 25 °C / min under the same atmosphere as the growth atmosphere to obtain a nitrogen-doped barium ferrite film (BaFe) with a thickness of approximately 45 nm. 12 O 17 N 1.2 ).

[0094] Tests showed that the nitrogen-doped barium ferrite film has good single-crystal properties, with a saturation magnetization of 262 emu / cc at room temperature.

[0095] Comparative Example 1

[0096] The only difference between Comparative Example 1 and Example 1 is that the deposition growth was carried out in a pure oxygen atmosphere to obtain a lithium ferrite film (LiFe5O8) with a thickness of about 30 nm.

[0097] Tests showed that the lithium ferrite film had poor crystal quality and high surface roughness, with a saturation magnetization of 153 emu / cc at room temperature.

[0098] Through comparative observation Figure 2 It can be observed that the nitrogen-doped lithium ferrite film a prepared in Example 1 is dark brown, while the lithium ferrite film b prepared in Comparative Example 1 is orange-yellow.

[0099] The nitrogen-doped lithium ferrite film prepared in Example 1 and the lithium ferrite film prepared in Comparative Example 1 were subjected to high-resolution XRD scanning and asymmetric (206) plane reciprocal space scanning tests. The results are as follows: Figure 3 As shown, nitrogen-doped lithium ferrite film a exhibits excellent single-crystal characteristics. Furthermore, the lattice constants both inside and outside the plane of nitrogen-doped lithium ferrite film a are slightly larger than those of lithium ferrite film b. This conforms to the general rule of lattice constant expansion after oxide nitridation, reflecting the slightly larger atomic radius of nitrogen-doped lithium ferrite film a. 3- Ion-substituted O 2- Lattice expansion of nitrogen-doped lithium ferrite films caused by ionization.

[0100] The magnetic properties of the nitrogen-doped lithium ferrite film prepared in Example 1 were compared with those of the lithium ferrite film prepared in Comparative Example 1. The results are as follows: Figure 4 As shown, it can be found that nitrogen-doped lithium ferrite films have similar soft magnetic properties to lithium ferrite films, and the room temperature saturation magnetization of nitrogen-doped lithium ferrite film a is significantly higher than that of lithium ferrite film b.

[0101] The dielectric properties of the nitrogen-doped lithium ferrite film a prepared in Example 1 and the lithium ferrite film b prepared in Comparative Example 1 were compared in the ultraviolet-visible-near-infrared bands. The results are as follows: Figure 5 As shown, it can be observed that the dielectric constant of nitrogen-doped lithium ferrite film a differs from that of lithium ferrite film b in the ultraviolet-visible-near-infrared band. Specifically, compared to the lithium ferrite film, the real part of the dielectric constant of nitrogen-doped lithium ferrite film a is significantly lower in the 200nm-600nm and 850nm-1600nm ranges; while in the 600nm-850nm range, the real part of the dielectric constant of nitrogen-doped lithium ferrite film a is higher. Furthermore, the imaginary part of the dielectric constant of nitrogen-doped lithium ferrite film a is significantly increased in the visible and near-infrared bands, indicating improved absorption capacity in these bands.

[0102] Furthermore, UV spectrophotometer measurements show that the bandgap of nitrogen-doped lithium ferrite film a differs from that of lithium ferrite film b. Specifically, the direct bandgap of nitrogen-doped lithium ferrite film a is 2.07 eV, and the indirect bandgap is 1.44 eV, while the direct bandgap of lithium ferrite film b is 2.35 eV, and the indirect bandgap is 1.94 eV. Electrical transport measurements also indicate that nitrogen-doped lithium ferrite film a exhibits significant semiconductor properties, with a conductivity reaching 21 S / cm at room temperature (300 K), while lithium ferrite film b is highly insulating, with a conductivity below 10 S / cm at room temperature (300 K). -6 S / cm.

[0103] Comparative Example 2

[0104] The only difference between Comparative Example 2 and Example 4 is that the deposition and growth were carried out in a pure oxygen atmosphere to obtain a bismuth ferrite film (BiFeO3) with a thickness of about 30 nm.

[0105] Tests showed that the bismuth ferrite film had poor crystal quality and high surface roughness, with a saturation magnetization of 9 emu / cc at room temperature.

[0106] Comparative Example 3

[0107] The only difference between Comparative Example 3 and Example 5 is that the deposition and growth were carried out in a pure oxygen atmosphere, resulting in a yttrium ferrite film (Y3Fe5O) with a thickness of approximately 50 nm. 12 ).

[0108] Tests showed that the yttrium ferrite film had poor crystal quality and high surface roughness, with a saturation magnetization of 115 emu / cc at room temperature.

[0109] Comparative Example 4

[0110] The only difference between Comparative Example 4 and Example 6 is that the deposition and growth were carried out in a pure oxygen atmosphere, resulting in a barium ferrite film (BaFe) with a thickness of approximately 45 nm. 12 O 19 ).

[0111] Tests showed that the barium ferrite film had poor crystal quality and high surface roughness, with a saturation magnetization of 230 emu / cc at room temperature.

[0112] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0113] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A nitrogen-doped ferrite thin film, characterized in that, The nitrogen-doped ferrite film exhibits single-crystal characteristics, and the chemical formula of the nitrogen-doped ferrite film is: (LiFe) 0.5 Fe2O 4-x N y , where 0 < x ≤ 2, 0 < y ≤ 1.5, and 0 < 2x - 3y ≤ 1; Alternatively, Y3Fe5O 12-x N y , where 0 < x ≤ 6, 0 < y ≤ 4, and 0 < 2x - 3y ≤ 5; Alternatively, BaFe 12 O 19-x N y , where 0 < x ≤ 10, 0 < y ≤ 7, and 0 < 2x - 3y ≤ 12.

2. The nitrogen-doped ferrite thin film according to claim 1, characterized in that, The thickness of the nitrogen-doped ferrite film is 1 nm-1 μm.

3. A method for preparing a nitrogen-doped ferrite thin film as described in any one of claims 1-2, characterized in that, Includes the following steps: We provide ferrite sputtering targets and single-crystal substrates; Under vacuum conditions, the temperature of the single crystal substrate is controlled, and thin film is grown on the single crystal substrate in a nitrogen-containing atmosphere. After cooling, a nitrogen-doped ferrite thin film is obtained.

4. The method for preparing nitrogen-doped ferrite thin films according to claim 3, characterized in that, The ferrite target material is selected from spinel ferrite, perovskite ferrite, garnet ferrite or hexagonal ferrite.

5. The method for preparing nitrogen-doped ferrite thin films according to claim 3, characterized in that, The thickness of the ferrite target is less than or equal to 3 mm.

6. The method for preparing nitrogen-doped ferrite thin films according to claim 3, characterized in that, The single-crystal substrate is selected from SrTiO3, LaAlO3, (La,Sr)(Al,Ta)O3, KTaO3, MgAl2O4, Al2O3, and Gd3Ga5O. 12 Y3Al5O 12 At least one of Si, SiC, GaN, and GaAs.

7. The method for preparing nitrogen-doped ferrite thin films according to claim 3, characterized in that, In the nitrogen-containing gas, the volume fraction of nitrogen is greater than or equal to 0.1%.

8. The method for preparing nitrogen-doped ferrite thin films according to claim 3, characterized in that, The back vacuum level before thin film growth begins is less than or equal to 10. -5 Torr; And / or, the pressure of nitrogen-containing gas during film growth is 0.1 Pa - 200 Pa; And / or, in the step of adjusting the temperature of the single crystal substrate, the temperature of the single crystal substrate is made to be greater than 25°C.

9. An electronic device comprising a nitrogen-doped ferrite thin film as described in any one of claims 1-2.

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