Electron-Energy-Loss Spectroscopy of Oxide Superconductor Bi2Sr 2CaCu 2O 8

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Abstract
Transmission electron-energy-loss spectra of the oxide superconductor Bi2Sr2CaCu2O8 have been taken from perfect crystalline areas (100 nmφ) in an energy range of 0–60 eV at temperatures of 30 K, 100 K and 300 K. A peak at about 0.6 eV was observed at these temperatures instead of a peak at about 1 eV which was reported to be a free-carrier plasmon peak. The dielectric function derived from the loss-function indicates that the peak at about 0.6 eV can be attributed not to a collective excitation (plasmon) but to an interband transition. The electron density which contributes to the peak has been calculated to be 2 ×1019 electron/cm3. The peaks and shoulders of the spectra (the loss-function) are assigned to individual interband transitions. The temperature dependence of ε 2 has been found around 2.5 eV and 5.5 eV.