MgO/Ag(100): Confined vibrational modes in the limit of ultrathin films
- 28 February 2003
- journal article
- research article
- Published by American Physical Society (APS) in Physical Review B
- Vol. 67 (7), 075420
- https://doi.org/10.1103/physrevb.67.075420
Abstract
The vibrational modes of clean MgO films are investigated vs film thickness by means of high-resolution electron energy-loss spectroscopy. For thin films (20–30 monolayers) we observe, in accord with the literature, the Fuchs-Kliewer phonon at and the Wallis mode at For ultrathin films standing wave optical phonons confined in the overlayer are present, whose frequencies depend strongly on film thickness. Comparison with theoretical calculations for MgO slabs on a perfect conductor shows that the experimental frequencies are lower than expected, indicating the presence of compressive stress. At and below one-monolayer thickness an intense loss peak at is observed.
Keywords
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