SYSTEMATIC DIFFERENCES AMONG NOMINAL REFERENCE DIELECTRIC FUNCTION SPECTRA FOR CRYSTALLINE SI AS DETERMINED BY SPECTROSCOPIC ELLIPSOMETRY

Results of the first systematic investigation of differences among ref erence-quality ellipsometrically measured pseudodielectric function (E ) spectra of crystalline Si are discussed. These data are nominally us ed to approximate the bulk dielectric function of this material for op tical modeling. In addition to the expected influence of residual over layers, we identify surface-local-field and energy-derivative effects even between spectra obtained for seemingly identical H-terminated sur faces. Model calculations indicate that these effects account for near ly all differences among spectra studied. The isotropic contribution t o the surface-local-field effect is also reported. (C) 1998 Elsevier S cience S.A.