We discuss ellipsometric measurements using synchrotron radiation and estimate the errors that are due to focusing light onto the sample. Our results lead to the conclusion that ellipsometry is a brightness experiment and can benefit considerably from the use of synchrotron radiation in the mid and far infrared. We report implementation of a synchrotron far-infrared ellipsometer at the U4IR beam line at the National Synchrotron Light Source, Brookhaven National Laboratory, covering the 50–700-cm−1 wave-number range. To illustrate the capability of our setup we have determined the complex dielectric function of the ionic insulator LiF and of the heavily doped semiconductor GaAs (n≈8×1018 cm−3). We also report direct measurements of the optical interplane conductivity of single crystalline La2CuO4+δ and a twinned YBa2Cu3O7 crystal. From these data, dynamic atomic effective charges have been determined for La2CuO4+δ.
© 1997 Optical Society of America
[Optical Society of America ]
J. Kircher, R. Henn, M. Cardona, P. L. Richards, and G. P. Williams, "Far-infrared ellipsometry using synchrotron radiation," J. Opt. Soc. Am. B 14, 705-712 (1997)