Anisotropic Dielectric Properties of Cesium-doped Tungsten Oxide Nanoparticles Studied by Electron Energy Loss Spectroscopy

Researchers from Tohoku University have made a significant discovery in the field of nanotechnology, exploring the anisotropic dielectric properties of cesium-doped tungsten oxide nanoparticles using electron energy loss spectroscopy (EELS). The study, published in the Journal of Applied Physics, has shed light on the importance of understanding the optical properties of nanoparticulate dispersions. By employing high-energy-resolution EELS, the researchers were able to evaluate the anisotropic dielectric responses of individual nanoparticles, providing valuable insights into their behavior.

Key Takeaways:

• The research team at Tohoku University used EELS to study the anisotropic dielectric properties of cesium-doped tungsten oxide nanoparticles, revealing anisotropic responses of individual nanoparticles.
• The EELS spectra showed peaks at around 1.3 and 0.9eV, depending on the beam conditions parallel or perpendicular to the c-axis, indicating the dielectric tensor components of (zz) and (xx).
• The peak energy in the parallel to c condition was larger than that in the perpendicular to c condition, which qualitatively agrees with optical reflection measurements using polarized light.
• The experimental values of peak energies and widths were smaller and larger than the theoretically evaluated values, respectively, which can be attributed to a damping of dipole oscillation by electronic excitations owing to oxygen vacancies.
• The peak energies of perpendicular to c and parallel to c interaction conditions varied in ranges of 0.7-1.0eV and 1.1-1.6eV, respectively, which supports the presence of ensemble inhomogeneity in dielectric responses of NPs.
• The results indicate that the anisotropy and inhomogeneity of dielectric response are important factors for understanding the optical properties of nanoparticulate dispersions.

Statistics:

• Peaks in EELS spectra were observed at around 1.3 and 0.9eV.
• Peak energy in the parallel to c condition was larger than that in the perpendicular to c condition.
• The experimental values of peak energies and widths were smaller and larger than the theoretically evaluated values, respectively.
• Peak energies of perpendicular to c and parallel to c interaction conditions varied in ranges of 0.7-1.0eV and 1.1-1.6eV, respectively.

Sources:

• Anisotropic Dielectric Properties and Ensemble Inhomogeneity of Cesium-doped Tungsten Oxide Nanoparticles Studied By Electron Energy Loss Spectroscopy. Journal of Applied Physics, 2020;128(8):083108.
• NewsRx. Researchers from Tohoku University Detail Findings in Nanoparticles (Anisotropic Dielectric Properties and Ensemble Inhomogeneity of Cesium-doped Tungsten Oxide Nanoparticles Studied By Electron Energy Loss Spectroscopy). Nanotechnology Weekly. October 5, 2020; p 4942.