研究目的
Investigating the core–shell structures in individual lead titanate ferroelectric nanostructures by tip-enhanced refractive index mapping.
研究成果
The study successfully imaged the core–shell structure of PbTiO3 nanoislands using TERS, revealing a ferroelectric core surrounded by a paraelectric shell. The spatial resolution of up to 3 nm allowed for the observation of permittivity changes at the grain boundaries, confirming the predicted phase transition. This approach provides a contact-free method for investigating individual nanoscale ferroelectrics, offering insights into their phase transition behaviors.
研究不足
The study's limitations include the partial occupation of the near-field volume by the sample surface, affecting the permittivity change measurement accuracy. The discrepancy between experimental and simulated gold emission maxima also indicates potential areas for optimization in the numerical simulation approach.
1：Experimental Design and Method Selection:
The study utilized tip-enhanced Raman spectroscopy (TERS) for imaging individual PbTiO3 nanoislands with a spatial resolution of ≈3 nm. The method leverages the gold-tip enhanced luminescence's spectral shift, dependent on the local refractive index, to image the grains composing the nanoislands.
2：Sample Selection and Data Sources:
The sample consisted of 30 nm thick PbTiO3 islands on a (111) platinized silicon substrate, prepared by chemical solution deposition (CSD).
3：List of Experimental Equipment and Materials:
Equipment included an AIST-NT Omegascope system with a Nanofinder 30 Raman spectrometer, a thermoelectrically cooled Andor CCD detector, and a 632.8 nm TEM00 He-Ne laser. Gold tips were electrochemically etched from a 200 μm 99.99% gold wire.
4：8 nm TEM00 He-Ne laser. Gold tips were electrochemically etched from a 200 μm 99% gold wire.
Experimental Procedures and Operational Workflow:
4. Experimental Procedures and Operational Workflow: Near-field measurements were performed with the gold tip in controlled distance over the Pt substrate and on PbTiO3 islands. The gold emission was fitted using a Voigt function and subtracted from the measured spectra to isolate the enhanced Raman signal.
5：Data Analysis Methods:
The enhanced Raman signal was analyzed to identify peaks corresponding to PbTiO3 modes. The shift of the gold emission peak was monitored to image the contrast between ferroelectric and paraelectric phases.
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