研究目的
Investigating the reversible control of physical properties via an oxygen-vacancy-driven topotactic transition in epitaxial La0.7Sr0.3MnO3?δ thin films.
研究成果
The study demonstrates the reversible control of physical properties via an oxygen-vacancy-driven topotactic transition in epitaxial La0.7Sr0.3MnO3?δ thin films. A novel intermediate phase with a noncentered crystal structure is observed for the first time during the topotactic phase conversion, indicating a distinctive transition route. The findings open an additional dimension to tune material properties via anion vacancy concentration, contributing to the field of defect engineering in resistive switching memories, redox catalysts, high ionic conductors, electrochemical sensing, and spintronic devices.
研究不足
The study focuses on epitaxial La0.7Sr0.3MnO3?δ thin films, and the findings may not be directly applicable to other material systems or film orientations. The intermediate phase observed is metastable and unstable in ambient atmosphere, which may limit its practical applications.
1：Experimental Design and Method Selection:
Epitaxial La0.7Sr0.3MnO3?δ thin films were grown on (001)-oriented SrTiO3 substrates by high oxygen pressure sputter deposition (HOPSD). The structural evolution from perovskite to brownmillerite was monitored during a post-annealing process using in situ X-ray diffraction (XRD). Polarized neutron reflectometry (PNR) was employed to probe the depth profile of both the nuclear and magnetic scattering length density.
2：7Sr3MnO3?δ thin films were grown on (001)-oriented SrTiO3 substrates by high oxygen pressure sputter deposition (HOPSD). The structural evolution from perovskite to brownmillerite was monitored during a post-annealing process using in situ X-ray diffraction (XRD). Polarized neutron reflectometry (PNR) was employed to probe the depth profile of both the nuclear and magnetic scattering length density.
Sample Selection and Data Sources:
2. Sample Selection and Data Sources: The samples were prepared at an oxygen partial pressure of 1.5 mbar, and a deposition temperature of 850 °C. The stoichiometry of the films was determined using Rutherford backscattering spectroscopy (RBS).
3：5 mbar, and a deposition temperature of 850 °C. The stoichiometry of the films was determined using Rutherford backscattering spectroscopy (RBS).
List of Experimental Equipment and Materials:
3. List of Experimental Equipment and Materials: Bruker D8 instrument for in situ XRD measurements, superconducting quantum interference device (SQUID) magnetometer (MPMS XL, Quantum Design) for magnetization measurements, quantum design physical properties measurement system (PPMS) for magnetotransport measurements, polarized magnetic reflectometer MARIA at the Heinz Maier-Leibnitz Zentrum (MLZ) for PNR measurements.
4：Experimental Procedures and Operational Workflow:
The samples were annealed at varying temperatures from 200 to 600 °C in a vacuum chamber (10?6 mbar) to systematically control the topotactic phase conversion speed. The reoxidation process was performed in the sputter chamber, in which gas type, flow rate, and pressure can be controlled.
5：Data Analysis Methods:
The reflectivity data collected at 10 and 150 K were fitted with the GenX program together in one model to ensure that the chemical scattering length density remains the same.
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