Growth and hydrogenation of epitaxial yttrium switchable mirrors on CaF2

Ernst S. Kooij, J.H. Rector, D.G. Nagengast, J.W.J. Kerssemakers, B. Dam, R. Griessen, A. Remhof, H. Zabel

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Abstract

Rutherford backscattering (RBS) ion channeling measurements and X-ray diffraction experiments are performed to study the epitaxial nature of as-deposited yttrium on CaF2111 substrates and the effect of hydrogenation on the crystalline quality. The RBS and X-ray results clearly demonstrate the unique epitaxial relation between as-deposited films and the substrate, which is preserved upon loading with hydrogen. X-Ray diffraction reveals: (i) a remarkably large lattice expansion in the direction normal to the substrate, which decreases with increasing film thickness; and (ii) an in-plane compression of the lattice. This peculiar result is related to the difference in thermal expansion coefficients of film and substrate. RBS ion channeling measurements reveal a thickness dependence of the mismatch-induced stresses. As expected, the stresses relax with increasing distance from the film/substrate interface, but surprisingly, even with films as thick as 400 nm considerable dechanneling is still observed at the film surface. Film quality, i.e. the film/substrate mismatch as well as the induced stresses and their relaxation, are discussed in relation to atomic force microscopy (AFM) results on these epitaxial films.
Original languageUndefined
Pages (from-to)131-142
Number of pages12
JournalThin solid films
Volume402
Issue number1-2
DOIs
Publication statusPublished - 2002

Keywords

  • Switchable mirrors
  • Rutherford backscattering spectroscopy (RBS)
  • Molecular beam epitaxy (MBE)
  • Yttrium
  • METIS-202554
  • IR-74793
  • Epitaxy
  • X-Ray Diffraction (XRD)

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