Method for preparing samarium-iron-nitrogen film

Abstract

The invention relates to a method for preparing a samarium-iron-nitrogen film, which comprises the following steps: S1, preparing a samarium-iron alloy target: mixing samarium and iron according to a certain molar ratio, smelting in a vacuum or inert gas environment to form a cast ingot, and carrying out hot isostatic pressing molding after mechanical pulverization and ball milling refinement; s2, the samarium-iron alloy target material is placed in a magnetron sputtering instrument cavity, argon and nitrogen mixed gas is introduced, the target material is bombarded through plasma, and a samarium-iron-nitrogen film is formed after deposition is conducted for a certain time at a certain substrate temperature; and S3, the deposited film is annealed in Ar or N2 or a mixed atmosphere of Ar and N2, the annealing temperature is 250-650 DEG C, and the annealing time is 0-5 hours. According to the preparation method, the sputtering gas is set as the mixed gas of Ar and N2, the N2 is used as the reaction gas, so that the N element enters the samarium-iron alloy film, and the film with the Th2Zn17 structure is prepared.

Description

Technical Field

[0001] The invention relates to the field of samarium iron nitrogen films, in particular to a method for preparing the samarium iron nitrogen films. Background Art

[0002] Permanent magnetic thin film materials are crucial for the development of future electronic information devices and intelligent equipment, and have been applied to many fields, such as computer hard disks, micro-electromechanical systems, and magnetic rotary encoders. Currently, the most widely used permanent magnetic material is the third-generation rare earth permanent magnetic material, neodymium iron boron (NdFeB)-based permanent magnet, which has a high thermal conductivity of up to 444kJ / m 3 Maximum energy product. However, the high demand and supply risks of rare earth materials such as Nd have prompted the search for alternative permanent magnet materials. Samarium-iron-based compounds are considered potential alternatives because some SmFe-based materials have low rare earth element content, which can reduce dependence on resources such as Nd.

[0003] In the research and application of high-performance permanent magnet materials, SmFeN materials have become a powerful alternative to NdFeB magnets due to their advantages in high-temperature stability, corrosion resistance, cost-effectiveness and environmental sustainability. SmFeN magnets have a higher Curie temperature (about 476°C), which is better than NdFeB (about 310°C), allowing them to maintain stable magnetic properties in high-temperature environments. Secondly, SmFeN magnets are more resistant to oxidation and corrosion than NdFeB, which usually requires additional coating protection. Therefore, thanks to the high-temperature stability, corrosion resistance and low cost of SmFeN films, SmFeN films show higher reliability and economy in applications such as high-temperature motors, micro-electromechanical systems and high-frequency devices.

[0004] Currently, the main methods for preparing SmFeN thin films include aerosol deposition and traditional magnetron sputtering. There are several difficulties that need to be overcome in the process of preparing SmFeN thin films.

[0005] Aerosol deposition utilizes a high-speed airflow to deposit micron-sized samarium iron nitride powder directly onto a substrate, forming a dense film. This method offers advantages such as a fast deposition rate, no need for high-temperature annealing, and suitability for large-area deposition. However, its preparation process also presents challenges. Mechanical impact of the powder during deposition can easily lead to microcracks or pores in the film, which not only affects the film's magnetic properties but also reduces its mechanical stability. Furthermore, controlling the film's magnetic anisotropy is difficult, limiting optimization of its performance.

[0006] The traditional magnetron sputtering method usually performs room temperature sputtering in an argon (Ar) atmosphere, followed by annealing crystallization at high temperature, or sputtering crystallization at 350°C or 400°C. The nitridation process is a nitridation treatment in an ammonia (NH3) / nitrogen (N2) mixed gas or N2. However, this method faces many challenges. First, the nitridation process usually needs to be carried out at high temperatures, and the use of nitrogen sources such as NH3 may lead to uneven nitridation and the formation of impurity phases, thereby affecting the magnetic properties of the film. In addition, nitridation may also cause stress accumulation in the film, leading to structural defects and decreased adhesion. Secondly, in terms of composition control, due to the different evaporation rates of Sm and Fe, it is easy for the composition to deviate from the ideal ratio, forming non-ideal phases, and reducing magnetic anisotropy and coercivity.

[0007] Therefore, we proposed a method for preparing samarium iron nitride thin films, which directly introduces a mixed gas of argon and nitrogen during the sputtering process to achieve simultaneous deposition and nitridation, so that the nitrogen element is evenly introduced during the deposition process, eliminating the subsequent nitridation step. This process simplification not only improves production efficiency, but also reduces the introduction of impurities and improves the purity of the film. Summary of the Invention

[0008] The purpose of the present invention is to overcome the shortcomings of the prior art and meet practical needs by providing a method for preparing samarium iron nitride thin films. This method solves the current aerosol deposition method, which uses a high-speed airflow to deposit micron-sized samarium iron nitride powder directly onto a substrate to form a dense film. This method has the advantages of fast deposition rate, no need for high-temperature annealing, and suitability for large-area deposition. However, its preparation process also faces challenges: due to the mechanical impact of the powder during the deposition process, microcracks or pores can easily appear in the film, which not only affects the magnetic properties of the film but also reduces its mechanical stability. In addition, the magnetic anisotropy of the film is difficult to control, which also limits the optimization of film performance. Typically, sputtering is performed at room temperature in an argon (Ar) atmosphere, followed by annealing and crystallization at high temperature, or sputtering and crystallization at 350°C or 400°C. The nitridation process is carried out in an ammonia (NH3) / nitrogen (N2) mixed gas or N2. This process with a nitridation process has many disadvantages. The nitridation process usually needs to be carried out at high temperatures, and the use of nitrogen sources such as NH3 may lead to uneven nitridation and the formation of impurity phases, thereby affecting the magnetic properties of the film. In addition, nitridation may also cause stress accumulation in the film, leading to structural defects and decreased adhesion. Secondly, in terms of composition control, due to the different evaporation rates of Sm and Fe, it is easy to cause the composition to deviate from the ideal ratio, forming non-ideal phases, and reducing magnetic anisotropy and coercivity.

[0009] In order to achieve the purpose of the present invention, the technical solution adopted by the present invention is to design a method for preparing a samarium iron nitrogen film, comprising the following steps:

[0010] S1. Preparation of samarium iron target: samarium and iron are mixed in a certain molar ratio, smelted in a vacuum or inert gas environment to form an ingot, and then mechanically crushed and ball-milled before hot isostatic pressing;

[0011] S2. Placing a samarium iron alloy target in a magnetron sputtering chamber, introducing a mixture of argon and nitrogen, bombarding the target with plasma, and forming a samarium iron nitrogen film after a certain deposition time at a certain substrate temperature;

[0012] S3. Anneal the deposited film in an atmosphere of Ar or N2 or a mixture of the two, with an annealing temperature of 250° C.-650° C. and an annealing time of 0-5 hours.

[0013] Preferably, in step S1, the ratio of samarium to iron in the target material is 2:17.

[0014] Preferably, in step S2, the distance between the target and the substrate is 10 cm.

[0015] Preferably, the total flow rate of the mixed gas in step S3 is 30 sccm, and the volume ratio of Ar / N2 is 29:1.

[0016] Preferably, in step S2, the sputtering gas pressure is 2.0 Pa and the sputtering power is 100 W.

[0017] Preferably, the temperature of the substrate in step S2 is room temperature.

[0018] Preferably, the annealing temperature in step S3 is 550°C.

[0019] Preferably, in step S2, the vacuum degree of the chamber before magnetron sputtering is evacuated to 8×10 -5 Below Pa, the pre-sputtering time is 5 minutes.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. The present invention directly introduces a mixed gas of argon and nitrogen during the sputtering process, so that the nitrogen element is evenly introduced during the deposition process, eliminating the subsequent nitridation step. This process simplification not only greatly improves production efficiency, but also reduces the introduction of impurities, thereby improving the purity of the film. Moreover, by precisely controlling the annealing temperature, the crystal structure and magnetic properties of the film can be further optimized. High-temperature annealing helps to improve the crystallinity of the film and enhance the magnetic anisotropy, thereby increasing the residual magnetization and saturation magnetization. This effectively solves many problems in traditional preparation methods and provides a better solution for the preparation and application of samarium iron nitrogen films. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1Schematic diagram of SEM and EDS results of the sample annealed in 550°C Ar atmosphere of the present invention;

[0023] Figure 2 This is a schematic diagram of the 550°C annealing XRD results of the present invention;

[0024] Figure 3 This is a schematic diagram of the 550°C annealing hysteresis loop results of the present invention;

[0025] Figure 4 Schematic diagram of SEM and EDS results of the sample annealed at 600°C in Ar atmosphere of the present invention;

[0026] Figure 5 This is a schematic diagram of the 600°C annealing XRD results of the present invention;

[0027] Figure 6 This is a schematic diagram of the 600°C annealing hysteresis loop results of the present invention;

[0028] Figure 7 Schematic diagram of SEM and EDS results of the sample annealed at 650°C in Ar atmosphere of the present invention;

[0029] Figure 8 This is a schematic diagram of the 650°C annealing XRD results of the present invention;

[0030] Figure 9 This is a schematic diagram of the 650°C annealing hysteresis loop results of the present invention;

[0031] Figure 10 This is a schematic diagram of the SEM and EDS results of the unannealed sample of the present invention;

[0032] Figure 11 This is a schematic diagram of the unannealed XRD results of the present invention;

[0033] Figure 12 This is a schematic diagram of the unannealed hysteresis loop results of the present invention. DETAILED DESCRIPTION

[0034] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0035] A method for preparing samarium iron nitrogen thin film, see Figures 1 to 9 , including the following steps:

[0036] S1. Preparation of Sm2Fe17 target: Samarium and iron are mixed in a molar ratio of 2:17, smelted in an argon environment to form an ingot, and then mechanically crushed and ball-milled before hot isostatic pressing;

[0037] S2. Place the Sm2Fe17 target in the chamber of a magnetron sputtering instrument, introduce a mixed gas of argon and nitrogen with a volume ratio of 29:1, and deposit it on a 001-oriented Si substrate for 2 hours to form a samarium iron nitrogen film;

[0038] S3. Anneal the deposited film in an Ar atmosphere at a temperature of 550° C., 600° C., or 650° C. for 10 min.

[0039] Specifically, in step S2 , the distance between the target and the substrate is 10 cm.

[0040] More specifically, in step S3 , the total flow rate of the mixed gas is 30 sccm, and the volume ratio of Ar / N 2 is 29:1.

[0041] Furthermore, in step S3, the sputtering gas pressure is 2.0 Pa, and the sputtering power is 100 W.

[0042] Furthermore, when the annealing temperature in step S4 is 550° C., the coercive field of the film is 115 Oe, the residual magnetization is 9.51 emu / g, and the saturation magnetization is 36.4 emu / g.

[0043] It is worth noting that when the annealing temperature in step S4 is 600° C., the coercive field of the film is 53 Oe, the residual magnetization is 17.55 emu / g, and the saturation magnetization is 49.7 emu / g.

[0044] It is worth noting that when the annealing temperature in step S4 is 650° C., the coercive field of the film is 33 Oe, the residual magnetization is 25.15 emu / g, and the saturation magnetization is 60.1 emu / g.

[0045] It is worth mentioning that in step S4, after 2 hours of deposition, the plasma is bombarded on the target material to deposit a samarium iron nitrogen film on the Si substrate.

[0046] It is worth mentioning that in step S3, the vacuum degree of the chamber before magnetron sputtering was evacuated to 8×10 -5 Below Pa, the pre-sputtering time is 5 minutes.

[0047] It is worth mentioning that the thickness of the Ti layer pre-sputtered in step S2 is 10 nm.

[0048] It should be noted that the model of the magnetron sputtering instrument is PVD-400.

[0049] Example 1

[0050] This embodiment uses magnetron sputtering to prepare samarium iron nitride thin films. The specific steps are as follows:

[0051] First, a Sm2Fe17 block was selected as the target and placed on the target holder in the magnetron sputtering chamber. Subsequently, a Si substrate with a (001) orientation was placed on the sample stage in the chamber, and the distance between the target and the substrate was precisely controlled to be 10 cm. After completing the above preparations, the chamber was sealed and evacuated until the vacuum level in the chamber reached 8×10 -5 Pa.

[0052] Next, Ar gas was introduced into the chamber at a flow rate of 20 sccm, and the pressure in the chamber was maintained at a stable 2.0 Pa. Before the actual sputtering, a 5-minute pre-sputtering operation was performed to remove impurities from the target surface. After the pre-sputtering, the sample shutter was opened and a 10 nm thick Ti layer was sputtered. After the sputtering was completed, the Ti target was turned off.

[0053] Afterwards, an Ar / N₂ mixture with a volume ratio of 29:1 was introduced into the chamber at a flow rate of 30 sccm, and the sputtering pressure was also set to 2.0 Pa. The magnetron sputtering instrument was powered on, the sputtering power set to 100 W, and a further 5-minute pre-sputtering period was performed. After the pre-sputtering period, the sample shutter was opened, and deposition sputtering began. The deposition process lasted for 2 hours. During this time, the plasma continuously bombarded the target, gradually depositing the SmFeN film on the Si substrate.

[0054] After the deposition is completed, the sample is taken out of the chamber and placed in a rapid thermal annealing furnace for annealing at 550°C in an Ar gas atmosphere. The annealing time is 10 minutes and the Ar gas flow rate is set to 2 L / min.

[0055] Test results

[0056] Ingredient distribution: reference Figure 1 After annealing at 550℃, the sample has a uniform distribution of components. Through relevant detection methods, it can be observed that Sm, Fe, and N are evenly distributed on the sample surface.

[0057] XRD analysis results: reference Figure 2 It can be clearly seen from the figure that Th2Zn 17 XRD peaks of phase structure.

[0058] Magnetic properties measurement results: Reference Figure 3The figure shows the in-plane (red) and out-of-plane (black) hysteresis loops of the sample, measured at room temperature using the vibrating sample magnetometer (VSM) module in the Physical Property Measurement System (PPMS). Analysis of the hysteresis loops indicates that the easy magnetization direction of the sample lies in-plane. Its specific magnetic properties are as follows: coercive field (Hc) of 115 Oe, remanent magnetization (Mr) of 9.51 emu / g, and saturation magnetization (Ms) of 36.4 emu / g.

[0059] Example 2

[0060] This embodiment uses magnetron sputtering to prepare samarium iron nitride thin films. The specific operation process is as follows:

[0061] First, a Sm2Fe17 block was selected as the target and placed on the target holder in the magnetron sputtering chamber. Subsequently, a Si substrate with a (001) orientation was placed on the sample stage in the chamber, and the distance between the target and the substrate was strictly controlled to be 10 cm. After completing this series of preparations, the chamber was sealed and the vacuum equipment was started until the vacuum level in the chamber reached 8×10 - 5 Pa.

[0062] Next, Ar gas was introduced into the chamber at a flow rate of 20 sccm, while the pressure in the chamber was maintained at a stable level of 2.0 Pa. Before the actual sputtering operation, a 5-minute pre-sputtering process was performed to remove any impurities on the target surface. After the pre-sputtering process, the sample shutter was opened, and a 10 nm thick Ti layer was sputtered. Once the Ti layer was sputtered, the Ti target sputtering was turned off.

[0063] Afterwards, an Ar / N₂ mixture with a volume ratio of 29:1 and a flow rate of 30 sccm was introduced into the chamber, and the sputtering pressure was also set to 2.0 Pa. The magnetron sputtering instrument was powered on, the sputtering power set to 100 W, and a 5-minute pre-sputtering period was performed. After the pre-sputtering period, the sample shutter was opened and deposition sputtering began, which lasted for 2 hours. During this period, the plasma continuously bombarded the target, gradually depositing the SmFeN film on the Si substrate.

[0064] After the deposition is completed, the sample is taken out of the chamber and placed in a rapid thermal annealing furnace for annealing in an Ar gas atmosphere at 600°C. The annealing time is 10 minutes, and the Ar gas flow rate is set to 2 L / min.

[0065] Test results

[0066] Ingredient distribution: reference Figure 4After annealing at 600℃, the sample showed a uniform distribution of components. Professional testing methods showed that Sm, Fe, and N were evenly distributed on the sample surface.

[0067] XRD analysis results: reference Figure 5 It can be clearly seen from the figure that Th2Zn 17 XRD peaks of phase structure.

[0068] Magnetic properties measurement results: Reference Figure 6 The figure shows the magnetization hysteresis curves of the sample at room temperature, measured with the applied magnetic field parallel to the film ( / / ) and perpendicular to the film (⊥). Analysis of the magnetization hysteresis curves indicates that the easy magnetization direction of the sample lies in the plane. Its specific magnetic properties are as follows: coercive field (Hc) of 53 Oe, remanent magnetization (Mr) of 17.55 emu / g, and saturation magnetization (Ms) of 49.7 emu / g.

[0069] Example 3

[0070] This embodiment adopts magnetron sputtering to prepare samarium iron nitride thin film, and the specific operation steps are as follows:

[0071] First, a Sm2Fe17 block was selected as the target and placed on the target holder in the magnetron sputtering chamber. Next, a (001) oriented Si substrate was placed on the sample stage in the chamber, and the distance between the target and the substrate was precisely controlled to be 10 cm. After completing the above preparations, the chamber was sealed and the vacuum equipment was started until the vacuum level in the chamber reached 8×10 -5 Pa.

[0072] Afterwards, Ar gas was introduced into the chamber at a flow rate of 20 sccm, and the pressure within the chamber was adjusted to 2.0 Pa. Before the actual sputtering operation, a 5-minute pre-sputtering process was performed to remove impurities from the target surface. After the pre-sputtering process, the sample shutter was opened, and sputtering of a 10 nm thick Ti layer began. Once the Ti layer was sputtered, the Ti target sputtering was turned off.

[0073] Then, an Ar / N₂ mixture with a volume ratio of 29:1 and a flow rate of 30 sccm was introduced into the chamber, and the sputtering pressure was set to 2.0 Pa. The magnetron sputtering instrument was powered on, the sputtering power set to 100 W, and a 5-minute pre-sputtering period was performed. After the pre-sputtering period, the sample shutter was opened and deposition sputtering began, which lasted for 2 hours. During this period, the plasma continuously bombarded the target, gradually depositing the SmFeN film on the Si substrate.

[0074] After the deposition is completed, the sample is taken out of the chamber and placed in a rapid thermal annealing furnace for annealing at 650°C in an Ar gas atmosphere. The annealing time is 10 minutes and the Ar gas flow rate is set to 2 L / min.

[0075] Test results

[0076] Ingredient distribution: reference Figure 7 After annealing at 650℃, the sample has a uniform distribution of components. Relevant detection methods show that Sm, Fe, and N are evenly distributed on the sample surface.

[0077] XRD analysis results: reference Figure 8 It can be clearly seen from the figure that Th2Zn appeared at the positions of 30°, 35° and 42°. 17 XRD peaks of phase structure.

[0078] Magnetic properties measurement results: Reference Figure 9 The figure shows the magnetization hysteresis curves of the sample at room temperature, measured with the applied magnetic field parallel to the film ( / / ) and perpendicular to the film (⊥). Analysis of the magnetization hysteresis curves indicates that the easy magnetization direction of the sample lies in the plane. Its specific magnetic properties are as follows: coercive field (Hc) of 33 Oe, remanent magnetization (Mr) of 25.15 emu / g, and saturation magnetization (Ms) of 60.1 emu / g.

[0079] Comparative Example 1

[0080] This comparative example adopts magnetron sputtering method to carry out the preparation of samarium iron nitrogen thin film, and the specific operation steps are as follows:

[0081] First, a Sm2Fe17 block was selected as the target and placed on the target holder in the magnetron sputtering chamber. A (001)-oriented Si substrate was then placed on the sample stage in the chamber, and the distance between the target and the substrate was precisely controlled to be 10 cm. After completing the preparations, the chamber was sealed and the vacuum equipment was started until the vacuum level in the chamber reached 8×10 -5 Pa.

[0082] Next, Ar gas was introduced into the chamber at a flow rate of 20 sccm, while the pressure in the chamber was maintained at a stable level of 2.0 Pa. Before the actual sputtering operation, a 5-minute pre-sputtering process was performed to remove any impurities on the target surface. After the pre-sputtering process, the sample shutter was opened, and a 10 nm thick Ti layer was sputtered. Once the Ti layer was sputtered, the Ti target sputtering was turned off.

[0083] Afterwards, an Ar / N2 mixed gas with a flow rate of 30 sccm and a volume ratio of 29:1 was introduced into the cavity, and the sputtering pressure was also set to 2.0 Pa. The power source of the magnetron sputtering instrument was started, the sputtering power was set to 100 W, and pre-sputtering was performed again for 5 minutes. After the pre-sputtering was completed, the sample baffle was opened and deposition sputtering was started. The deposition process lasted for 2 hours. During this period, the plasma continued to bombard the target material, causing the samarium iron nitrogen film to be gradually deposited and formed on the Si substrate. In this comparative example, the prepared sample was not annealed.

[0084] Test results

[0085] Ingredient distribution: reference Figure 10 For the unannealed samples, it can be observed through relevant detection methods that its composition is evenly distributed, and Sm, Fe and N elements are evenly distributed on the sample surface.

[0086] XRD analysis results: reference Figure 11 It can be clearly seen from the figure that only the alpha-Fe phase was detected, and the expected Th2Zn phase was not found. 17 Target phase of the structure.

[0087] Magnetic properties measurement results: Reference Figure 12 The figure shows the in-plane (red) and out-of-plane (black) hysteresis loops of the sample, measured at room temperature using the vibrating sample magnetometer (VSM) module in the Physical Property Measurement System (PPMS). Analysis of the hysteresis loops indicates that the easy magnetization direction of the sample lies in-plane. Its specific magnetic properties are as follows: coercive field (Hc) of 46 Oe, remanent magnetization (Mr) of 1.91 emu / g, and saturation magnetization (Ms) of 44.3 emu / g.

[0088] In addition, the components designed in the present invention are all universal standard parts or components known to those skilled in the art. Their structures and principles can be known to those skilled in the art through technical manuals or conventional experimental methods. They can be fully implemented by those skilled in the art. Needless to say, the content protected by the present invention does not involve improvements to internal structures and methods.

[0089] The embodiments disclosed in the present invention are preferred embodiments, but are not limited to them. Ordinary technicians in this field can easily understand the spirit of the present invention based on the above embodiments and make different extensions and changes. As long as they do not deviate from the spirit of the present invention, they are all within the scope of protection of the present invention.

Claims

1. A method for preparing a samarium iron nitrogen thin film, characterized in that: The following steps are involved: S1. Preparation of samarium iron target: samarium and iron are mixed in a certain molar ratio, smelted in a vacuum or inert gas environment to form an ingot, and then mechanically crushed and ball-milled before hot isostatic pressing; S2. Placing a samarium iron alloy target in a magnetron sputtering chamber, introducing a mixture of argon and nitrogen, bombarding the target with plasma, and forming a samarium iron nitrogen film after a certain deposition time at a certain substrate temperature; S3. Anneal the deposited film in an atmosphere of Ar or N2 or a mixture of the two, with an annealing temperature of 250° C.-650° C. and an annealing time of 0-5 hours.

2. The method for preparing a samarium iron nitrogen thin film according to claim 1, wherein: In step S1, the molar ratio of samarium to iron in the target material is 20:1 to 1:

20.

3. The method for preparing a samarium iron nitrogen thin film according to claim 1, wherein: In step S2, the distance between the target and the substrate is 0-50 cm.

4. The method for preparing a samarium iron nitrogen thin film according to claim 1, wherein: The partial pressure ratio of the mixed gas in step S2 is Ar / N2 in a range of 1:3 to 49:

1.

5. The method for preparing a samarium iron nitrogen thin film according to claim 1, wherein: In step S2, the sputtering pressure is 0.0001-100 Pa, the sputtering power is 1-2000 W, and the temperature of the substrate is 20° C.-650° C.

6. The method for preparing a samarium iron nitride thin film according to claim 1, wherein: When the annealing temperature in step S3 is 250-650° C., the coercive field of the film is 10-10000 Oe, and the residual magnetization is 1-150 emu / g.

7. The method for preparing a samarium iron nitrogen thin film according to claim 1, wherein: When the annealing time in step S3 is 0-5 hours and the annealing temperature is 250-650°C, the crystal structure of the film is Th2Zn 17 structure.

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