研究目的
Investigating the effect of pulsed laser deposition parameters on the as-deposited amorphous precursor titania thin films, which subsequently crystallize into stable and metastable TiO2 polymorphs upon annealing, to understand the underlying mechanism that stabilizes brookite over its stable counterparts, rutile and anatase.
研究成果
The study demonstrates that oxygen deficiency in amorphous TiOX precursors, controlled by varying the oxygen pressure during PLD, significantly influences the crystallization of TiO2 polymorphs. Brookite formation is favored at intermediate oxygen pressures, while rutile and anatase dominate at low and high pressures, respectively. This suggests that manipulating the internal energy and structure of the amorphous precursor can direct phase selectivity, offering a pathway to synthesize metastable phases with desirable properties.
研究不足
The study focuses on the effect of oxygen deficiency and film thickness on polymorph formation but does not fully explore the interaction between these factors. Additionally, the range of oxygen pressures and film thicknesses may not cover all possible conditions for polymorph formation.
1：Experimental Design and Method Selection:
The study employs pulsed laser deposition (PLD) to grow amorphous TiOX thin films on fused silica substrates at room temperature, followed by rapid thermal annealing in flowing nitrogen to crystallize the films. The oxygen pressure (pO2) during deposition is varied to control the stoichiometry of the amorphous precursors.
2：Sample Selection and Data Sources:
Films of varying thicknesses (5 to 190 nm) are grown at different oxygen pressures (0.1 to 10 mTorr) to study the effect of oxygen deficiency on polymorph formation.
3：1 to 10 mTorr) to study the effect of oxygen deficiency on polymorph formation.
List of Experimental Equipment and Materials:
3. List of Experimental Equipment and Materials: PLD system, fused silica substrates, rapid thermal processing system, Raman spectrometer, transmission electron microscope (TEM), scanning transmission electron microscope (STEM), electron energy-loss spectrometer (EELS), Rutherford backscattering spectrometry (RBS) system, X-ray diffraction (XRD) setup.
4：Experimental Procedures and Operational Workflow:
Films are annealed in a rapid thermal processing system under flowing N2. Raman spectroscopy is used to identify the crystalline phases. TEM and STEM are used for structural characterization. EELS and RBS are used for compositional analysis.
5：Raman spectroscopy is used to identify the crystalline phases. TEM and STEM are used for structural characterization. EELS and RBS are used for compositional analysis.
Data Analysis Methods:
5. Data Analysis Methods: Phase fractions are calculated from Raman spectra. Film stoichiometry is determined from EELS and RBS data. XRD is used for structural verification.
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