Post-treatment method for improving crystallization quality of perovskite oxide film
Through the post-treatment method of alternating high-temperature annealing of oxygen/vacuum/oxygen atmosphere, the crystal quality of perovskite oxide film is improved, the performance inconsistency caused by defects in the film preparation process in the prior art is solved, and the crystal quality improvement of efficient and low-cost is achieved.
Patent Information
- Application Number
- CN202510744325.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-05
- Publication Date
- 2025-09-02
AI Technical Summary
The prior art is difficult to effectively improve the crystal quality of perovskite oxide films, especially due to difficult-to-control defects such as vacancies, dislocations, layering errors, etc. during the preparation process, resulting in performance inconsistency and degradation.
The post-treatment method of alternating high-temperature annealing of oxygen/vacuum/oxygen atmosphere is adopted to eliminate structural defects in the film through the reversible conversion of "perovskite phase-calcium-ironite phase-perovskite phase".
It significantly improves the crystallization quality of perovskite oxide films, reduces equipment costs, is suitable for a variety of film preparation methods, and does not require additional equipment, improving the consistency of film performance.
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Abstract
Description
Technical Field
[0001] The invention belongs to the field of preparation of oxide films, and in particular relates to a post-processing method for improving the crystallization quality of perovskite oxide films. Background Art
[0002] Perovskite oxides possess more complex crystal structures, stoichiometric relationships, and multiple oxidation states than semiconductor materials. The coupling between multiple degrees of freedom, including lattice, charge, spin, and orbital, within the system makes them ideal materials for functional device design. Compared to bulk materials, perovskite oxide thin films offer low dimensionality and heterogeneous interfaces, allowing for artificial structural design and multi-field control of physical problems such as quantum confinement, quantum coherence, quantum fluctuations, topological electronic states, electron-electron interactions, spin-orbit coupling, and symmetry breaking.
[0003] Basic research and device applications in perovskite oxides require thin films with consistent performance and high crystalline quality. However, the difficulty in precisely controlling the film preparation process and the lattice mismatch between the substrate and the film often introduce numerous defects such as vacancies, dislocations, and stacking faults within the oxide film. These defects significantly affect the film's crystalline quality and degrade its performance. Furthermore, the random nature of these defects significantly impacts the consistency of the film's performance.
[0004] Current methods for improving film quality mainly focus on controlling the oxygen pressure during film preparation, designing the substrate lattice mismatch, and precisely controlling heteroepitaxial growth parameters (such as deposition rate, substrate temperature gradient, etc.). However, all of the above methods have certain limitations. For example, methods that reduce substrate lattice mismatch not only restrict material selection, but also fail to effectively utilize the strain introduced by the lattice mismatch to control material properties. Precise control of the growth process will not only place higher demands on film preparation equipment and significantly increase the equipment cost for film preparation, but will also reduce the efficiency of film preparation. Therefore, exploring efficient and low-cost methods to improve the crystallization quality of perovskite oxide films is one of the key issues that need to be addressed in this field. Summary of the Invention
[0005] The present invention proposes a thin film post-processing method based on structural reversible phase transition, which can improve the crystallization quality of perovskite oxide thin films in an efficient and low-cost manner.
[0006] The present invention achieves the above-mentioned purpose by adopting the following technical solutions:
[0007] A post-processing method for improving the crystallization quality of a perovskite oxide thin film comprises the following steps:
[0008] S1, annealing the perovskite oxide film at high temperature in an oxygen atmosphere;
[0009] S2, annealing the perovskite oxide film at a high temperature in a vacuum environment to convert it from a perovskite phase to a brownfield phase;
[0010] S3. annealing the perovskite oxide film at a high temperature in an oxygen atmosphere to convert it from a calcium iron ore phase to a perovskite phase.
[0011] Furthermore, the thin film material is selected from perovskite oxides that can undergo reversible conversion from "perovskite phase to calcium iron ore".
[0012] Furthermore, when the perovskite oxide film is subjected to high-temperature annealing in an oxygen atmosphere, the annealing temperature ranges from 300 to 1000° C., the annealing time ranges from 10 to 300 minutes, and the oxygen pressure ranges from 10 to 1000 kPa.
[0013] Furthermore, the perovskite oxide film is subjected to high temperature annealing in a vacuum environment to convert it from the perovskite phase to the brown iron phase. The annealing temperature ranges from 300 to 1000°C, the annealing time ranges from 10 to 300 minutes, and the ambient vacuum range is 10 -1 ~10 -6 Pa.
[0014] Furthermore, the perovskite oxide film is subjected to high-temperature annealing in an oxygen atmosphere to convert it from the brown iron ore phase to the perovskite phase. The annealing temperature ranges from 300 to 1000° C., the annealing time ranges from 10 to 300 minutes, and the oxygen pressure ranges from 10 to 1000 kPa.
[0015] Advantages of the present invention:
[0016] The present invention induces the reversible transformation of the material "perovskite phase-calcium iron phase-perovskite phase" in perovskite oxide through alternating high-temperature annealing in oxygen / vacuum / oxygen atmosphere. This method can effectively eliminate structural defects in the film that are difficult to eliminate through conventional annealing methods, thereby greatly improving the crystallization quality of the film.
[0017] The present invention optimizes the structure of pre-prepared perovskite oxide thin films through post-processing to improve their crystalline quality. This post-processing approach is applicable to various thin film preparation methods and can reduce the requirements for precise control of the growth process and lattice matching between the substrate and the film in the preparation of high-quality thin films.
[0018] The method of oxygen / vacuum / oxygen atmosphere alternating high-temperature annealing proposed in the present invention requires simple equipment to implement and can be directly performed on common thin film preparation equipment such as molecular beam epitaxy, pulsed laser deposition, magnetron sputtering, chemical vapor deposition, etc., without the need for additional new equipment. It has the advantages of simple method and low cost. BRIEF DESCRIPTION OF THE DRAWINGS
[0019] Figure 1 It is La prepared on SrTiO3 single crystal substrate based on pulsed laser deposition technology. 0.67 Sr 0.33 MnO 3-σ The (LSMO) film samples were not annealed, after the first annealing (101kPa oxygen pressure / 800℃ / 80 minutes), after the second annealing (10 -4 XRD θ-2θ scanning patterns of the steel sheet after annealing for 1 hour at 101 kPa vacuum / 800°C / 80 minutes and after the third annealing (101 kPa oxygen pressure / 800°C / 80 minutes);
[0020] Figure 2 This is the XRDω scanning spectrum of the LSMO (002) crystal plane of the perovskite phase of the LSMO / SrTiO3 sample after annealing in oxygen atmosphere only and after alternating annealing in oxygen / vacuum / oxygen atmosphere;
[0021] Figure 3 The XRD θ-2θ scanning patterns of LSMO / SrTiO3 samples after annealing in oxygen atmosphere for 80 minutes, 160 minutes, and oxygen / vacuum / oxygen alternating annealing, respectively;
[0022] Figure 4 It is a LaAlO3 single crystal substrate prepared by pulsed laser deposition technology. 0.67 Sr 0.33 MnO 3-σ XRD θ-2θ scanning patterns of (LSMO) thin film samples without annealing, after 80 minutes and 160 minutes of oxygen atmosphere annealing, and after oxygen / vacuum / oxygen alternating annealing;
[0023] Figure 5 This is the XRDω scanning spectrum of the LSMO (002) crystal plane of the perovskite phase of the LSMO / LaAlO3 sample after annealing in oxygen atmosphere only and after alternating annealing in oxygen / vacuum / oxygen atmosphere; DETAILED DESCRIPTION
[0024] The following describes in detail the implementation and features of the technical solution of the present invention in conjunction with specific embodiments to help readers understand the spirit and beneficial effects of the present invention, but does not constitute any limitation on the scope of implementation of the present invention.
[0025] Example 1:
[0026] La grown on (001) SrTiO3 single crystal substrate by pulsed laser deposition 0.67 Sr 0.33 MnO 3-σTaking the (LSMO) thin film sample as an example, the post-treatment method for improving the crystallization quality of the thin film proposed in the present invention is implemented. The thickness of the SrTiO3 substrate is 0.5mm, and the thickness of the LSMO film is 50nm. The XRD θ-2θ scanning results of the film are shown in Figure 2. Figure 1 As shown, it shows that the LSMO film grows along the c-axis direction and has a perovskite phase structure.
[0027] The specific steps of post-processing are as follows:
[0028] S1. Anneal the LSMO film at high temperature in an oxygen atmosphere
[0029] The LSMO / SrTiO3 thin film sample was placed in a muffle furnace and annealed at high temperature in a high-purity oxygen atmosphere at 800°C, 80 minutes, and an oxygen pressure of 101 kPa. After annealing, the sample was characterized by XRD. XRD θ-2θ scanning results ( Figure 1 ) shows that the annealed film presents a perovskite phase structure (La 0.67 Sr 0.33 MnO3, PV-LSMO) remains unchanged from before annealing. Furthermore, the LSMO (002) diffraction peak shifts to the right compared to the pre-annealing state, and the broadening of the diffraction peak decreases. This suggests that high-temperature annealing in an oxygen atmosphere reduces defects such as oxygen vacancies in the film, causing the lattice to shrink and initially improving the film's crystalline quality.
[0030] S2. Anneal the LSMO film at high temperature in a vacuum environment to convert it from the perovskite phase to the brown iron phase.
[0031] The film sample was placed in a vacuum chamber containing a heater and annealed at high temperature under high vacuum conditions. The annealing temperature was 800°C, the annealing time was 80 minutes, and the vacuum degree was 10 -4 After annealing, the film samples were characterized by XRD, and the XRDθ-2θ scanning results ( Figure 1 ) shows that the film after vacuum annealing presents a brown iron phase structure (La 0.67 Sr 0.33 MnO 2.5 ,BM-LSMO). This indicates that high-temperature annealing in a high vacuum environment causes the film material to be continuously oxygen-deficient, and a structural phase transition induced by oxygen vacancies occurs, from the perovskite phase to the brownfield phase.
[0032] S3, annealing the LSMO film at high temperature in an oxygen atmosphere to convert it from the brown iron phase to the perovskite phase
[0033] The film sample was placed in a muffle furnace and annealed at high temperature in a high-purity oxygen atmosphere at 800°C, 80 minutes, and an oxygen pressure of 101 kPa. After annealing, the sample was characterized by XRD. XRD θ-2θ scanning results ( Figure 1 ) shows that the film now presents a perovskite phase structure. This indicates that high-temperature annealing in a high-purity oxygen atmosphere causes the BM-LSMO of the perovskite phase to be converted back into the PV-LSMO of the perovskite phase. Compared with the state after only completing the first oxygen atmosphere annealing in step S1, the LSMO (002) crystal plane diffraction peak at this time continues to shift to the right. XRD rocking curve results (such as Figure 2 ) shows that the half-height width of the LSMO (002) diffraction peak after oxygen / vacuum / oxygen annealing is 0.358°, which is significantly smaller than 0.428° after only completing the first annealing in step S1.
[0034] These results demonstrate that after the perovskite-calcium iron ore-perovskite phase transition, the film's lattice continues to shrink, reflecting a continued reduction in film defects and further improvement in the film's crystalline quality. This demonstrates that the proposed alternating high-temperature annealing method of oxygen / vacuum / oxygen atmosphere induces a reversible perovskite-calcium iron ore-perovskite phase transition in the perovskite oxide. This method effectively eliminates defects in the film that are difficult to eliminate through conventional annealing methods, significantly improving the film's crystalline quality. This topological phase transition cycle can effectively improve the crystalline quality of thin films.
[0035] Comparative Example 1:
[0036] The LSMO film sample in Example 1 was subjected to only conventional high-temperature annealing in an oxygen atmosphere. The advantages of the post-treatment method proposed in this patent were compared by comparing the effects of conventional annealing alone and the post-treatment method proposed in this patent on the improvement of film crystallization quality by inducing the "perovskite phase-perovskite phase-perovskite phase" transformation through alternating oxygen / vacuum / oxygen atmosphere annealing.
[0037] After completing step S1 in Example 1, the LSMO / SrTiO3 thin film sample in Example 1 was annealed again with the same parameters as step S1 to further extend the annealing time. At this time, the thin film sample was annealed for a total of 160 minutes at a temperature of 800°C and an oxygen pressure of 101 kPa. The thin film sample after the second annealing was characterized by XRD scanning. XRD θ-2θ scanning results (such as Figure 3The results (shown in Figure 2) show that extending the annealing time by a factor of 1 does not significantly shift the LSMO (002) diffraction peak. This suggests that extending the high-temperature annealing time in an oxygen atmosphere cannot further improve the film's crystalline quality. However, using the post-treatment method described in this invention, alternating annealing in oxygen / vacuum / oxygen atmospheres, the LSMO (002) diffraction peak shifts further to the right.
[0038] This result shows that conventional high-temperature annealing post-treatment in an oxygen atmosphere can only reduce some defects such as oxygen vacancies, while the post-treatment method proposed in the present invention, using structural reversible phase transition, can eliminate structural defects that cannot be eliminated by traditional annealing methods, and significantly improve the crystallization quality.
[0039] Example 2:
[0040] For thin films with in-plane compressive strain, the post-treatment method proposed in this invention is performed on a LSMO thin film sample grown on a (001) LaAlO3 single crystal substrate. The thickness of the LaAlO3 substrate is 0.5 mm, and the thickness of the LSMO film is 50 nm. The XRD θ-2θ scanning results of the film are shown in Figure 2. Figure 4 As shown, it shows that the LSMO film is epitaxially grown along the c-axis direction, has an excellent crystal orientation, and the LSMO film is a perovskite phase structure.
[0041] The specific steps of post-processing are as follows:
[0042] S1. Anneal the LSMO film at high temperature in an oxygen atmosphere
[0043] The LSMO / LaAlO3 thin film sample was placed in a muffle furnace and annealed at high temperature in a high-purity oxygen atmosphere at 800°C, 80 minutes, and an oxygen pressure of 101 kPa. After annealing, the sample was characterized by XRD. XRD θ-2θ scanning results ( Figure 4 ) shows that the annealed film presents a perovskite phase structure (La 0.67 Sr 0.33 MnO3, PV-LSMO) remains the same as before annealing. Meanwhile, the LSMO (002) diffraction peak shifts to the right compared to the state before annealing. This indicates that high-temperature annealing in an oxygen atmosphere reduces defects such as oxygen vacancies in the film, causing the lattice to shrink and initially improving the film's crystalline quality.
[0044] After the LSMO / LaAlO3 film sample was annealed for 80 minutes under oxygen annealing, it was annealed again with the same parameters to further extend the annealing time. The film sample was annealed for a total of 160 minutes at a temperature of 800°C and an oxygen pressure of 101 kPa. Figure 4) shows that extending the annealing time does not cause a significant change in the LSMO (002) crystal plane diffraction peak. This indicates that extending the high-temperature annealing time in an oxygen atmosphere cannot further improve the crystallization quality of the film.
[0045] S2. Anneal the LSMO film at high temperature in a vacuum environment to convert it from the perovskite phase to the brown iron phase.
[0046] The film sample was placed in a vacuum chamber containing a heater and annealed at high temperature under high vacuum conditions. The annealing temperature was 800°C, the annealing time was 80 minutes, and the vacuum degree was 10 -4 Vacuum high-temperature annealing induces continuous oxygen deficiency in the thin film material, causing it to transform from the perovskite phase to the brownfield phase.
[0047] S3, annealing the LSMO film at high temperature in an oxygen atmosphere to convert it from the brown iron phase to the perovskite phase
[0048] The film sample was placed in a muffle furnace and annealed at high temperature in a high-purity oxygen atmosphere at 800°C, 80 minutes, and an oxygen pressure of 101 kPa. After annealing, the sample was characterized by XRD. XRD θ-2θ scanning results ( Figure 4 ) shows that the film now presents a perovskite phase structure. This indicates that high-temperature annealing in a high-purity oxygen atmosphere causes the BM-LSMO of the perovskite phase to be converted back into the PV-LSMO of the perovskite phase. Compared with the state after only oxygen atmosphere annealing, the LSMO (002) crystal plane diffraction peak at this time continues to shift to the right. XRD rocking curve results (such as Figure 5 The results show that the half-height width of the LSMO (002) diffraction peak after oxygen / vacuum / oxygen annealing is 0.154°, which is significantly smaller than the 0.0792° after only completing the 80-minute annealing in oxygen atmosphere in step S1. These results show that after the transformation of "perovskite phase-calcium iron ore phase-perovskite phase", the lattice of the film continues to shrink, reflecting that the defects in the film continue to decrease and the crystallization quality of the film is further improved. This fully proves that the alternating high-temperature annealing method of oxygen / vacuum / oxygen atmosphere can effectively eliminate defects in LSMO films in an in-plane compressive strain state that are difficult to eliminate by conventional annealing methods, greatly improving the crystallization quality of the film, indicating that the invention has universal applicability.
Claims
1. A post-processing method for improving the crystallization quality of perovskite oxide thin films, characterized in that The steps include: S1, annealing the perovskite oxide film at high temperature in an oxygen atmosphere; S2, annealing the perovskite oxide film at a high temperature in a vacuum environment to convert it from a perovskite phase to a brownfield phase; S3. annealing the perovskite oxide film at a high temperature in an oxygen atmosphere to convert it from a calcium iron ore phase to a perovskite phase.
2. The post-treatment method for improving the crystallization quality of a perovskite oxide thin film according to claim 1, characterized in that: The thin film material is made of perovskite oxide that can undergo reversible conversion from "perovskite to calcium iron ore".
3. The post-treatment method for improving the crystallization quality of a perovskite oxide thin film according to claim 1, characterized in that: When the perovskite oxide film is subjected to high-temperature annealing in an oxygen atmosphere, the annealing temperature ranges from 300 to 1000° C., the annealing time ranges from 10 to 300 minutes, and the oxygen pressure ranges from 10 to 1000 kPa.
4. The post-treatment method for improving the crystallization quality of a perovskite oxide thin film according to claim 1, characterized in that: When the perovskite oxide film is annealed at high temperature in a vacuum environment to transform it from the perovskite phase to the brown iron phase, the annealing temperature range is 300-1000°C, the annealing time range is 10-300 minutes, and the ambient vacuum range is 10 -1 ~10 -6 Pa.
5. The post-treatment method for improving the crystallization quality of a perovskite oxide thin film according to claim 1, characterized in that: When the perovskite oxide film is subjected to high-temperature annealing in an oxygen atmosphere to convert it from a perovskite phase to a perovskite phase, the annealing temperature ranges from 300 to 1000° C., the annealing time ranges from 10 to 300 minutes, and the oxygen pressure ranges from 10 to 1000 kPa.