OPTICAL-CONSTANTS OF THE NOBLE-METALS DETERMINED BY REFLECTION ELECTRON-ENERGY LOSS SPECTROSCOPY

The optical constants for Cu, Ag, and Au determined by reflection electron energy loss spectroscopy (REELS) using a data treatment method described in the previous paper in this Journal are reported. The purpose of this study is to further test the data treatment method on less free-electron-like metals. The method involves removal of surface effects by deconvolution of data taken with low-energy electrons (200 eV) from data taken with higher energy electrons (1500 eV). The low- and high-energy electron experimental spectra are discussed along with the resulting optical constants. It is found that, although the surface loss contribution to the high-energy electron data is not readily apparent, its contribution does affect the results of the Kramers-Kronig analysis used to determine the complex dielectric function. Thus, some account must taken of the surface loss contribution in order to obtain quantitative information about the optical constants. Along with surface effects, plural-scattering contributions to the spectral response are also removed using deconvolution procedures. Comparison of these results to literature values demonstrates that the data treatment method is successful in closely approximating the optical constants for Cu, Ag, and Au. © 1990.