ELECTRON-ENERGY-LOSS SPECTROSCOPY OF OXIDE SUPERCONDUCTOR BI2SR2CACU2O8

Transmission electron-energy-loss spectra of the oxide superconductor Bi2Sr2CaCu2O8 have been taken from perfect crystalline areas (100 nm p hi) in an energy range of 0-60 eV at temperature of 30 K, 100 K and 30 0 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 plasm on peak, The dielectric function derived from thr loss-function indica tes that the peak at about 0.6 eV can be attributed not to a collectiv e excitation (plasmon) but to an interband transition. The electron de nsity which contributes to the peak has been calculated to be 2 x 10(1 9) electron/cm(3). The peaks and shoulders of the spectra (the loss-fu nction) are assigned to individual interband transitions. The temperat ure dependence of epsilon(2) has been found around 2.5 eV and 5.5 eV.