title: Ellipsometry with polarisation analysis at cryogenic temperatures inside a vacuum chamber.
abstract: In this paper we describe a new variant of null ellipsometry to determine thicknesses and optical properties of thin films on a substrate at cryogenic temperatures. In the PCSA arrangement of ellipsometry the polarizer and the compensator are placed before the substrate and the analyzer after it. Usually, in the null ellipsometry the polarizer and the analyzer are rotated to find the searched minimum in intensity. In our variant we rotate the polarizer and the compensator instead, both being placed in the incoming beam before the substrate. Therefore the polarisation analysis of the reflected beam can be realized by an analyzer at fixed orientation. We developed this method for investigations of thin cryogenic films inside a vacuum chamber where the analyzer and detector had to be placed inside the cold shield at a temperature of T ≈ 90 K close to the substrate. All other optical components were installed at the incoming beam line outside the vacuum chamber, including all components which need to be rotated during the measurements. Our null ellipsometry variant has been tested with condensed krypton films on a highly oriented pyrolytic graphite substrate (HOPG) at a temperature of T ≈ 25 K. We show that it is possible to determine the indices of refraction of condensed krypton and of the HOPG substrate as well as thickness of krypton films with reasonable accuracy.
authors.affiliation: Institut für Kernphysik, Westfälische Wilhelms-Universität Münster, D-48149 Münster, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Bauer
authors.affiliation: Institut für Kernphysik, Westfälische Wilhelms-Universität Münster, D-48149 Münster, Germany.
authors.forename: B
authors.initials: B
authors.lastname: Grees
authors.affiliation: Institut für Kernphysik, Westfälische Wilhelms-Universität Münster, D-48149 Münster, Germany.
authors.forename: D
authors.initials: D
authors.lastname: Spitzer
authors.affiliation: Institut für Kernphysik, Westfälische Wilhelms-Universität Münster, D-48149 Münster, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Beck
authors.affiliation: Institut für Kernphysik, Westfälische Wilhelms-Universität Münster, D-48149 Münster, Germany.
authors.forename: R
authors.initials: R
authors.lastname: Bottesch
authors.affiliation: Institut für Kernphysik, Westfälische Wilhelms-Universität Münster, D-48149 Münster, Germany.
authors.forename: H-W
authors.initials: HW
authors.lastname: Ortjohann
authors.affiliation: Institut für Kernphysik, Westfälische Wilhelms-Universität Münster, D-48149 Münster, Germany.
authors.forename: B
authors.initials: B
authors.lastname: Ostrick
authors.affiliation: Institut für Kernphysik, Westfälische Wilhelms-Universität Münster, D-48149 Münster, Germany.
authors.forename: T
authors.initials: T
authors.lastname: Schäfer
authors.affiliation: Department of Physics, College of Science, Swansea University, Singleton Park, Swansea SA2 8DU, United Kingdom.
authors.forename: H H
authors.initials: HH
authors.lastname: Telle
authors.affiliation: Institut für Kernphysik, Westfälische Wilhelms-Universität Münster, D-48149 Münster, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Wegmann
authors.affiliation: Institut für Kernphysik, Westfälische Wilhelms-Universität Münster, D-48149 Münster, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Zbořil
authors.affiliation: Institut für Kernphysik, Westfälische Wilhelms-Universität Münster, D-48149 Münster, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Weinheimer