Structural transitions and relaxation processes during the epitaxial growth of ultrathin CaF2 films on Si(111)
The structure and morphology of ultrathin lattice matched CaF2 films of very few monolayers thickness, which were deposited on Si(111) substrates by molecular-beam epitaxy, have been studied in situ by synchrotron based grazing incidence x-ray diffraction. Even for the thinnest investigated film of...
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| Format: | Article |
| Language: | en_US |
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American Physical Society
2011
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| Online Access: | http://hdl.handle.net/1721.1/64978 |
| _version_ | 1811077572120805376 |
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| author | Deiter, Carsten Bierkandt, Markus Klust, Andreas Kumpf, Christian Su, Yixi Bunk, Oliver Feidenhans’l, Robert Wollschlager, Joachim |
| author2 | Massachusetts Institute of Technology. Department of Chemistry |
| author_facet | Massachusetts Institute of Technology. Department of Chemistry Deiter, Carsten Bierkandt, Markus Klust, Andreas Kumpf, Christian Su, Yixi Bunk, Oliver Feidenhans’l, Robert Wollschlager, Joachim |
| author_sort | Deiter, Carsten |
| collection | MIT |
| description | The structure and morphology of ultrathin lattice matched CaF2 films of very few monolayers thickness, which were deposited on Si(111) substrates by molecular-beam epitaxy, have been studied in situ by synchrotron based grazing incidence x-ray diffraction. Even for the thinnest investigated film of three monolayers thickness, the in-plane structure of the CaF2 film is determined by a lateral separation in two domains: a pseudomorphic phase assuming the lateral lattice constant of the Si(111) substrate and a completely relaxed phase. Analysis of the crystal truncation rods verifies that both phases adopt the entire homogeneous CaF2 film thickness. Therefore, we propose that atomic steps of the substrate bypass the nucleation barrier for the formation of (Shockley partial) dislocations so that the film starts to relax below the classical critical film thickness. While the relaxed phase assumes also the CaF2 bulk lattice constant for the vertical direction, the vertical lattice constant of the pseudomorphic phase increases due to the compressive lateral strain at the interface. This vertical expansion of the pseudomorphic phase, however, is larger than expected from the elastic constants of the CaF2 bulk. The fraction of the pseudomorphic CaF2 phase decreases with increasing film thickness. The interface between the pseudomorphic CaF2 phase and the Si(111) substrate is characterized by Ca on T4 sites, a smaller distance between the Si(111) substrate and the CaF interface layer and an expanded layer distance between CaF interface layer and the completely stoichiometric CaF2 film. |
| first_indexed | 2024-09-23T10:45:09Z |
| format | Article |
| id | mit-1721.1/64978 |
| institution | Massachusetts Institute of Technology |
| language | en_US |
| last_indexed | 2024-09-23T10:45:09Z |
| publishDate | 2011 |
| publisher | American Physical Society |
| record_format | dspace |
| spelling | mit-1721.1/649782022-09-27T14:42:59Z Structural transitions and relaxation processes during the epitaxial growth of ultrathin CaF2 films on Si(111) Deiter, Carsten Bierkandt, Markus Klust, Andreas Kumpf, Christian Su, Yixi Bunk, Oliver Feidenhans’l, Robert Wollschlager, Joachim Massachusetts Institute of Technology. Department of Chemistry Klust, Andreas Klust, Andreas The structure and morphology of ultrathin lattice matched CaF2 films of very few monolayers thickness, which were deposited on Si(111) substrates by molecular-beam epitaxy, have been studied in situ by synchrotron based grazing incidence x-ray diffraction. Even for the thinnest investigated film of three monolayers thickness, the in-plane structure of the CaF2 film is determined by a lateral separation in two domains: a pseudomorphic phase assuming the lateral lattice constant of the Si(111) substrate and a completely relaxed phase. Analysis of the crystal truncation rods verifies that both phases adopt the entire homogeneous CaF2 film thickness. Therefore, we propose that atomic steps of the substrate bypass the nucleation barrier for the formation of (Shockley partial) dislocations so that the film starts to relax below the classical critical film thickness. While the relaxed phase assumes also the CaF2 bulk lattice constant for the vertical direction, the vertical lattice constant of the pseudomorphic phase increases due to the compressive lateral strain at the interface. This vertical expansion of the pseudomorphic phase, however, is larger than expected from the elastic constants of the CaF2 bulk. The fraction of the pseudomorphic CaF2 phase decreases with increasing film thickness. The interface between the pseudomorphic CaF2 phase and the Si(111) substrate is characterized by Ca on T4 sites, a smaller distance between the Si(111) substrate and the CaF interface layer and an expanded layer distance between CaF interface layer and the completely stoichiometric CaF2 film. 2011-07-28T18:27:24Z 2011-07-28T18:27:24Z 2010-08 2010-03 Article http://purl.org/eprint/type/JournalArticle http://hdl.handle.net/1721.1/64978 Deiter, Carsten et al. “Structural Transitions and Relaxation Processes During the Epitaxial Growth of Ultrathin CaF2 Films on Si(111).” Physical Review B 82.8 (2010) : 085449. © 2010 The American Physical Society en_US http://dx.doi.org/10.1103/PhysRevB.82.085449 Physical Review B Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use. application/pdf American Physical Society APS |
| spellingShingle | Deiter, Carsten Bierkandt, Markus Klust, Andreas Kumpf, Christian Su, Yixi Bunk, Oliver Feidenhans’l, Robert Wollschlager, Joachim Structural transitions and relaxation processes during the epitaxial growth of ultrathin CaF2 films on Si(111) |
| title | Structural transitions and relaxation processes during the epitaxial growth of ultrathin CaF2 films on Si(111) |
| title_full | Structural transitions and relaxation processes during the epitaxial growth of ultrathin CaF2 films on Si(111) |
| title_fullStr | Structural transitions and relaxation processes during the epitaxial growth of ultrathin CaF2 films on Si(111) |
| title_full_unstemmed | Structural transitions and relaxation processes during the epitaxial growth of ultrathin CaF2 films on Si(111) |
| title_short | Structural transitions and relaxation processes during the epitaxial growth of ultrathin CaF2 films on Si(111) |
| title_sort | structural transitions and relaxation processes during the epitaxial growth of ultrathin caf2 films on si 111 |
| url | http://hdl.handle.net/1721.1/64978 |
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