A transition metal oxide thin film epitaxially grown on a LaSrAlTaO3 substrate and its preparation method

Abstract

The application belongs to the technical field of thin film deposition, and provides a transition metal oxide thin film epitaxially grown on a LaSrAlTaO3 substrate and a preparation method thereof. The application adopts a transition metal oxide target, epitaxially grows the transition metal oxide thin film on the LaSrAlTaO3 substrate based on a pulse laser deposition technology, and accurately designs pulse laser deposition parameters, such as a growth temperature of 700 DEG C, an oxygen pressure of 100 mTorr, a pulse laser repetition frequency of 2 Hz, and a pulse laser energy density of 1.23 J / cm 2 The application can prepare the transition metal oxide thin film with high crystallinity, few defects and excellent surface morphology by using a conventional pulse laser deposition device, thereby providing a basic condition for researching and designing functional devices based on the transition metal oxide thin film, and the application is expected to be widely applied in the fields of catalysis, energy and microelectronic devices.

Description

Technical Field

[0001] This invention belongs to the field of thin film deposition technology, and particularly relates to a transition metal oxide thin film epitaxially grown on a LaSrAlTaO3 substrate and its preparation method. Background Technology

[0002] Double perovskite transition metal oxides (lanthanum-nickel-iron oxide) are highly promising ferromagnetic semiconductor materials with significant application prospects in spintronic devices and memories. However, the performance of this material is extremely sensitive to stoichiometry, particularly the content of lanthanum (La) at the A-site. In existing pulsed laser deposition processes, the differences in the scattering behavior of elements in the plasma plume easily lead to deviations in the La content of the deposited film, severely limiting its performance. When the La content is excessive, the excess La atoms cannot enter the perovskite lattice and tend to precipitate as La₂O₃ impurities on the film surface. These precipitates form surface particles, greatly increasing the surface roughness of the film and causing interlayer short circuits or interface scattering problems in subsequent device fabrication. Furthermore, in actual epitaxial growth, the film often faces significant stress accumulation. If this interface stress cannot be released, the film will exhibit an island-like growth pattern in the early stages of growth, resulting in increased surface roughness and the formation of penetrating dislocations. These structural defects severely scatter charge carriers and spins, thus limiting device performance.

[0003] Therefore, how can we develop a transition metal oxide La that can effectively suppress La composition deviation, achieve precise stoichiometry, and produce a smooth surface while maintaining the basic properties of the material? x Ni 0.5 Fe 0.5 The preparation method of O3 (x=1.0 or 0.9) thin films is a technical problem that urgently needs to be solved in this field. To this end, the present invention proposes a method for epitaxially growing transition metal oxide thin films on LaSrAlTaO3 substrates and preparing the same. Summary of the Invention

[0004] The purpose of this invention is to provide a transition metal oxide thin film epitaxially grown on a LaSrAlTaO3 substrate and its preparation method, so as to solve the technical problems of severe compositional segregation and numerous large particle defects on the surface of transition metal oxide thin films in the prior art.

[0005] The objective of this invention is achieved through the following technical solution: A method for preparing a transition metal oxide thin film epitaxially grown on a LaSrAlTaO3 substrate includes the following steps: Step 1: Substrate loading and parameter preset; The LaSrAlTaO3 substrate was placed in the cavity of the pulsed laser deposition system, and the substrate temperature was adjusted to 650-700℃, while the oxygen pressure in the cavity was adjusted to 75-375 mTorr. Step 2: Pulsed laser deposition to prepare transition metal oxide thin films; A KrF excimer laser was used at a wavelength of 248 nm, a pulse repetition rate of 2-5 Hz, and an energy density of 1.0-2.0 J / cm² on a transition metal oxide target. 2 Under certain conditions, the transition metal oxide target is bombarded to generate plasma. The plasma is deposited on the surface of the LaSrAlTaO3 substrate and epitaxially grown to form a transition metal oxide thin film. Step 3: In-situ annealing and cooling of the substrate and sample acquisition; After growth is complete, pulsed laser bombardment is stopped, and the film is cooled to room temperature in situ to obtain a transition metal oxide film.

[0006] Furthermore, in step 1, the LaSrAlTaO3 substrate is a (001) LaSrAlTaO3 substrate.

[0007] Furthermore, in step 1, the substrate temperature is adjusted to 700 ℃ and the oxygen pressure inside the cavity is adjusted to 100 mTorr.

[0008] Furthermore, in step 2, the transition metal oxide target is composed of lanthanum, nickel, iron, and oxygen, and the stoichiometric ratio of lanthanum, nickel, iron, and oxygen atoms is x:0.5:0.5:3, where x is the amount of A-site vacancy, which takes a value of 1.0 or 0.9.

[0009] Furthermore, in step 2, during the pulsed laser deposition process, the transition metal oxide target rotates around its central normal and simultaneously performs small-angle reciprocating motion in a plane parallel to the LaSrAlTaO3 substrate.

[0010] Furthermore, in step 2, the pulsed laser repetition frequency is 2 Hz, and the energy density acting on the transition metal oxide target is 1.23 J / cm². 2 The growth time is 1 hour.

[0011] Furthermore, in step 3, the mixture is cooled in situ to room temperature at a rate of 10 °C / min.

[0012] A transition metal oxide thin film prepared according to the above-described method for preparing a transition metal oxide thin film epitaxially grown on a LaSrAlTaO3 substrate.

[0013] Furthermore, the chemical formula of the transition metal oxide thin film is La. x Ni 0.5 Fe0.5 O3, where x is the amount of vacancy at position A, with a value of 1.0 or 0.9.

[0014] Furthermore, when x is 0.9, the atoms in the transition metal oxide film are neatly arranged with no obvious dislocations.

[0015] Compared with the prior art, the beneficial effects of the present invention are: This invention employs a transition metal oxide target, composed of lanthanum-nickel-iron-oxygen, to epitaxially grow a transition metal oxide thin film on a LaSrAlTaO3 substrate using pulsed laser deposition technology. Precise design of the pulsed laser deposition parameters successfully locked the optimal coupling window between oxygen pressure and laser energy density. Within this window, the plasma plume generated by the interaction between the laser and the target possesses moderate kinetic energy, ensuring that La, Ni, and Fe elements are transported to the substrate surface in a strictly stoichiometric ratio. This effectively suppresses La composition deviation, resulting in a high-quality thin film with precise stoichiometry and a smooth surface. This invention further discovers that by intentionally introducing trace amounts of A-site (La) deficiencies (such as La...),... 0.9 Ni 0.5 Fe 0.5 O3 not only did not damage the material structure, but also significantly improved the overall quality of the film. Specifically, the introduction of A-site vacancies helps to release the lattice mismatch stress between the film and the substrate, reduce the dislocation density, and at the same time promote the surface migration of B-site cations (Ni / Fe), improving their order. Therefore, this invention can prepare La transition metal oxides with high crystallinity, few defects, and excellent surface morphology. x Ni 0.5 Fe 0.5 O3 (x=1.0 or 0.9) thin films provide a foundation for the research and design of functional devices based on transition metal oxide thin films, and are expected to be widely used in catalysis, energy and microelectronic devices. Attached Figure Description

[0016] Figure 1 This is a flowchart illustrating the preparation method of transition metal oxide thin films epitaxially grown on a LaSrAlTaO3 substrate.

[0017] Figure 2 The LaSrAlTaO3 substrate epitaxially grown on the LaSrAlTaO3 substrate using pulsed laser deposition technology in Example 1 is an example of this. 1.0 Ni 0.5 Fe 0.5 X-ray diffraction pattern of O3 thin film.

[0018] Figure 3 The LaSrAlTaO3 substrate epitaxially grown on the LaSrAlTaO3 substrate using pulsed laser deposition technology in Example 2 is an example of this. 0.9 Ni0.5 Fe 0.5 X-ray diffraction pattern of O3 thin film.

[0019] Figure 4 This invention relates to the epitaxial growth of LaSrAlTaO3 substrates on LaSrAlTaO3 substrates using pulsed laser deposition technology. 1.0 Ni 0.5 Fe 0.5 Characterization of the spherical aberration microstructure of the O3 thin film.

[0020] Figure 5 This invention relates to the epitaxial growth of LaSrAlTaO3 substrates on LaSrAlTaO3 substrates using pulsed laser deposition technology. 0.9 Ni 0.5 Fe 0.5 Characterization of the spherical aberration microstructure of the O3 thin film. Detailed Implementation

[0021] To provide a clearer understanding of the technical features, objectives, and beneficial effects of this invention, the technical solution of this invention is described in detail below, but this should not be construed as limiting the scope of implementation of this invention. Unless otherwise specified, the methods used in this invention are conventional methods in this technical field. In this invention, materials, reagents, or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0022] The specific implementation of the present invention will be described in detail below with reference to specific embodiments.

[0023] Example 1: Epitaxial growth of La based on pulsed laser deposition technology 1.0 Ni 0.5 Fe 0.5 O3 thin film; In this embodiment, pulsed laser deposition (PLD) technology is used to epitaxially grow La on a LaSrAlTaO3 substrate (selecting a (001) LaSrAlTaO3 substrate). 1.0 Ni 0.5 Fe 0.5 The specific process for O3 thin film manufacturing is as follows: Step 1: Substrate loading and parameter preset: The LaSrAlTaO3 substrate was placed into the PLD system cavity, and the substrate temperature was adjusted to 700 ℃, while the oxygen pressure in the cavity was adjusted to 100 mTorr.

[0024] Step 2: Pulsed laser deposition to prepare transition metal oxide thin films; A KrF excimer laser was used at a wavelength of 248 nm, a pulse repetition rate of 2 Hz, and an energy density of 1.23 J / cm² on a transition metal oxide target. 2 Under certain conditions, a transition metal oxide target, composed of lanthanum, nickel, iron, and oxygen (both the target and substrate were purchased from Hefei Single Crystal Materials Technology Co., Ltd.; in this embodiment, the stoichiometric ratio of lanthanum, nickel, iron, and oxygen atoms in the transition metal oxide target is 1.0:0.5:0.5:3), is bombarded to generate plasma. The plasma is deposited onto the surface of a LaSrAlTaO3 substrate and epitaxially grown for 1 hour to form a transition metal oxide thin film (in this embodiment, it is LaSrAlTaO3). 1.0 Ni 0.5 Fe 0.5 (O3 thin film). During pulsed laser deposition, the transition metal oxide target rotates around its central normal while simultaneously reciprocating at a small angle in a plane parallel to the substrate to ensure the uniformity of film composition and thickness. The energy density window is determined based on the ablation threshold of La and the backsputtering effect, with the aim of suppressing excessive evaporation or insufficient deposition of the La component.

[0025] Step 3: In-situ annealing and cooling of the substrate and sample acquisition; After growth was complete, pulsed laser bombardment was stopped, and the substrate was cooled to room temperature in situ at a rate of 10 °C / min, ultimately yielding LaSrAlTaO3 epitaxially grown on the substrate. 1.0 Ni 0.5 Fe 0.5 O3 thin film.

[0026] The La prepared in this embodiment 1.0 Ni 0.5 Fe 0.5 X-ray diffraction tests were performed on the O3 thin film, and the results are as follows: Figure 2 As shown in the figure, the film exhibits a single perovskite phase structure, and no impurity phase peaks were observed in the sample, indicating that within this compositional variation range, La vacancies are accommodated by the perovskite structure, forming a stable solid solution structure. The diffraction peaks of the film and the substrate show a clear correspondence, confirming that the film achieved high-quality epitaxial growth on the substrate surface. Magnified observation of the (002) main peak reveals high-resolution thickness fringes surrounding the Bragg peak, indicating that the film has extremely high coherence in the growth direction, and the film / substrate interface achieves atomic-level flatness. No impurity phase diffraction signals such as NiO, Fe2O3, or La2O3 were detected across the entire spectrum, strongly demonstrating the precise control capability of the stoichiometry of the method of this invention.

[0027] Example 2: Epitaxial growth of La based on pulsed laser deposition technology 0.9 Ni 0.5 Fe0.5 O3 thin film; In this embodiment, La is epitaxially grown on a LaSrAlTaO3 substrate (selected as (001) LaSrAlTaO3 substrate) using PLD technology. 0.9 Ni 0.5 Fe 0.5 The specific process for O3 thin film manufacturing is as follows: Step 1: Substrate loading and parameter preset; The LaSrAlTaO3 substrate was placed into the PLD system cavity, and the substrate temperature was adjusted to 700 ℃, while the oxygen pressure in the cavity was adjusted to 100 mTorr.

[0028] Step 2: Pulsed laser deposition to prepare transition metal oxide thin films; A KrF excimer laser was used at a wavelength of 248 nm, a pulse repetition rate of 2 Hz, and an energy density of 1.23 J / cm² on a transition metal oxide target. 2 Under certain conditions, a transition metal oxide target, composed of lanthanum, nickel, iron, and oxygen (both the target and substrate were purchased from Hefei Single Crystal Materials Technology Co., Ltd.; in this embodiment, the stoichiometric ratio of lanthanum, nickel, iron, and oxygen atoms in the transition metal oxide target is 0.9:0.5:0.5:3), is bombarded to generate plasma on the transition metal oxide target. The plasma is deposited onto the surface of the LaSrAlTaO3 substrate and epitaxially grown for 1 hour to form a transition metal oxide thin film (in this embodiment, it is LaSrAlTaO3). 0.9 Ni 0.5 Fe 0.5 (O3 thin film). During pulsed laser deposition, the transition metal oxide target rotates around its central normal while simultaneously reciprocating at a small angle in a plane parallel to the substrate to ensure the uniformity of film composition and thickness. The energy density window is determined based on the ablation threshold of La and the backsputtering effect, with the aim of suppressing excessive evaporation or insufficient deposition of the La component.

[0029] Step 3: In-situ annealing and cooling of the substrate and sample acquisition; After growth was complete, pulsed laser bombardment was stopped, and the substrate was cooled to room temperature in situ at a rate of 10 °C / min, ultimately yielding LaSrAlTaO3 epitaxially grown on the substrate. 0.9 Ni 0.5 Fe 0.5 O3 thin film.

[0030] The La prepared in this embodiment 0.9 Ni 0.5 Fe 0.5 X-ray diffraction tests were performed on the O3 thin film, and the results are as follows: Figure 3As shown in the figure, the diffraction peaks of the thin film and the substrate exhibit a significant paired coexistence characteristic. Specifically, in addition to the strong (001) and (002) peaks from the substrate, there are also peaks corresponding to La. 0.9 Ni 0.5 Fe 0.5 The (001) and (002) diffraction peaks of the O3 thin film. This strict correspondence between the substrate and the film diffraction peaks strongly demonstrates that, under this specific stoichiometry, the film successfully overcomes lattice distortion or amorphization that may be caused by compositional fluctuations. The high intensity and sharp peak shape of the film diffraction peaks further confirm that its internal lattice arrangement is highly ordered, its crystallinity is excellent, and no amorphization or stray orientation growth has occurred.

[0031] Example 3: La 1.0 Ni 0.5 Fe 0.5 O3 thin film and La 0.9 Ni 0.5 Fe 0.5 Characterization of the spherical aberration microstructure of O3 thin films; This embodiment focuses on the La prepared in Example 1. 1.0 Ni 0.5 Fe 0.5 O3 thin film and La prepared in Example 2 0.9 Ni 0.5 Fe 0.5 The spherical aberration microstructure of the O3 thin film was characterized, and the characterization results are as follows: Figure 4 , Figure 5 As shown. Figure 4 It can be observed that: La 1.0 Ni 0.5 Fe 0.5 Although the O3 thin film maintained the perovskite structure overall, structural defects were clearly observed in localized areas. Figure 5 It can be observed that: La 0.9 Ni 0.5 Fe 0.5 The O3 thin film exhibits a well-organized atomic arrangement with no obvious dislocations observed. It can be observed that introducing A-site defects not only does not damage the material structure but also significantly improves the overall quality of the film. The introduction of the A-site vacancy amount x can be used to release the lattice mismatch stress between the film and the substrate and reduce the dislocation density within the film. Simultaneously, A-site vacancies promote the surface mobility of B-site cations (Ni / Fe) during growth, thereby improving the cation order of Ni / Fe. Therefore, pulsed laser deposition technology can be used to prepare impurity-free, high-quality transition metal oxides La. x Ni 0.5 Fe 0.5O3 (x=1.0 or 0.9) thin films are of great significance for material growth and can be widely used in fields such as catalysis, energy, and microelectronic devices.

[0032] The above are merely preferred embodiments of the present invention. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the present invention.

Claims

1. A method for preparing a transition metal oxide thin film epitaxially grown on a LaSrAlTaO3 substrate, characterized in that, Includes the following steps: Step 1: Substrate loading and parameter preset; The LaSrAlTaO3 substrate was placed in the cavity of the pulsed laser deposition system, and the substrate temperature was adjusted to 650-700 ℃, while the oxygen pressure in the cavity was adjusted to 75-375 mTorr. Step 2: Pulsed laser deposition to prepare transition metal oxide thin films; A KrF excimer laser was used at a wavelength of 248 nm, a pulse repetition rate of 2-5 Hz, and an energy density of 1.0-2.0 J / cm² on a transition metal oxide target. 2 Under certain conditions, the transition metal oxide target is bombarded to generate plasma. The plasma is deposited on the surface of the LaSrAlTaO3 substrate and epitaxially grown to form a transition metal oxide thin film. Step 3: In-situ annealing and cooling of the substrate and sample acquisition; After growth is complete, pulsed laser bombardment is stopped, and the film is cooled to room temperature in situ to obtain a transition metal oxide film.

2. The method for preparing a transition metal oxide thin film epitaxially grown on a LaSrAlTaO3 substrate according to claim 1, characterized in that, In step 1, the LaSrAlTaO3 substrate is a (001) LaSrAlTaO3 substrate.

3. The method for preparing a transition metal oxide thin film epitaxially grown on a LaSrAlTaO3 substrate according to claim 1, characterized in that, In step 1, the substrate temperature is adjusted to 700 ℃ and the oxygen pressure inside the cavity is adjusted to 100 mTorr.

4. The method for preparing a transition metal oxide thin film epitaxially grown on a LaSrAlTaO3 substrate according to claim 1, characterized in that, In step 2, the transition metal oxide target is composed of lanthanum, nickel, iron, and oxygen, and the stoichiometric ratio of lanthanum, nickel, iron, and oxygen atoms is x:0.5:0.5:3, where x is the amount of A-site vacancy, which takes the value of 1.0 or 0.

9.

5. The method for preparing a transition metal oxide thin film epitaxially grown on a LaSrAlTaO3 substrate according to claim 1, characterized in that, In step 2, during the pulsed laser deposition process, the transition metal oxide target rotates around its central normal and simultaneously reciprocates in a plane parallel to the LaSrAlTaO3 substrate.

6. The method for preparing a transition metal oxide thin film epitaxially grown on a LaSrAlTaO3 substrate according to claim 1, characterized in that, In step 2, the pulsed laser repetition frequency is 2 Hz, and the energy density acting on the transition metal oxide target is 1.23 J / cm². 2 The growth time is 1 hour.

7. The method for preparing a transition metal oxide thin film epitaxially grown on a LaSrAlTaO3 substrate according to claim 1, characterized in that, In step 3, the mixture is cooled to room temperature in situ at a rate of 10 °C / min.

8. A transition metal oxide thin film prepared by the method for preparing a transition metal oxide thin film epitaxially grown on a LaSrAlTaO3 substrate according to any one of claims 1 to 7.

9. The transition metal oxide thin film according to claim 8, characterized in that, The chemical formula of the transition metal oxide thin film is La. x Ni 0.5 Fe 0.5 O3, where x is the amount of vacancy at position A, with a value of 1.0 or 0.

9.

10. The transition metal oxide thin film according to claim 9, characterized in that, When x is 0.9, the atoms of the transition metal oxide film are arranged neatly with no obvious dislocations.

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