High Energy-Resolution Electron Energy-Loss Spectroscopy Study of Electronic Structures of Barium Titanate Nanocrystals

概要

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High energy-resolution electron energy-loss spectra were obtained from barium titanate (BaTiO3) nanocrystals (BTNCs), which were synthesized by chemical vapor deposition using inductively coupled plasma. Onset energies of spectral intensities were 3.2 eV for 34 nm BTNCs and 3.5 eV for 6 nm BTNCs. This indicates an increase in the bandgap energy of BaTiO3 with a decrease in crystal sizes. Those onset energies obtained from 90 nm specimen areas showed an excellent agreement with those estimated by previously reported optical measurements. Volume plasmon peaks were observed at 26.5 eV for 34 nm BTNCs and 25 eV for 6 nm BTNCs. Dielectric functions of the BTNCs were derived from loss-functions by Kramers–Kronig analysis using the refractivity of bulk BaTiO3 ($=2.4$). The peaks of $\text{O 2p}\rightarrow\text{Ti 3d}$ (t2g) transitions in the imaginary part of dielectric function ($\varepsilon_{2}$) were observed at 3.3 eV for 34 nm BTNCs and 3.8 eV for 6 nm BTNCs. Those of $\text{O 2p}\rightarrow\text{Ti 3d}$ (eg) transitions were at 7.8 eV for 34 nm BTNCs and 6.6 eV for 6 nm BTNCs.
Published by the Japan Society of Applied Physics through the Institute of Pure and Applied Physicsの論文
2005-10-15