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.
- Switchable mirrors
- Rutherford backscattering spectroscopy (RBS)
- Molecular beam epitaxy (MBE)
- X-Ray Diffraction (XRD)
Kooij, E. S., Rector, J. H., Nagengast, D. G., Kerssemakers, J. W. J., Dam, B., Griessen, R., ... Zabel, H. (2002). Growth and hydrogenation of epitaxial yttrium switchable mirrors on CaF2. Thin solid films, 402(1-2), 131-142. https://doi.org/10.1016/S0040-6090(01)01711-4