Modeling of the Lattice Dynamics in Strontium Titanate Films of Various Thicknesses: Raman Scattering Studies
While the bulk strontium titanate (STO) crystal characteristics are relatively well known, ultrathin perovskites’ nanostructure, chemical composition, and crystallinity are quite complex and challenging to understand in detail. In our study, the DFT methods were used for modelling the Raman spectra...
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| author | Veera Krasnenko Alexander Platonenko Aleksandr Liivand Leonid L. Rusevich Yuri A. Mastrikov Guntars Zvejnieks Maksim Sokolov Eugene A. Kotomin |
| author_facet | Veera Krasnenko Alexander Platonenko Aleksandr Liivand Leonid L. Rusevich Yuri A. Mastrikov Guntars Zvejnieks Maksim Sokolov Eugene A. Kotomin |
| author_sort | Veera Krasnenko |
| collection | DOAJ |
| description | While the bulk strontium titanate (STO) crystal characteristics are relatively well known, ultrathin perovskites’ nanostructure, chemical composition, and crystallinity are quite complex and challenging to understand in detail. In our study, the DFT methods were used for modelling the Raman spectra of the STO bulk (space group I4/mcm) and 5–21-layer thin films (layer group p4/mbm) in tetragonal phase with different thicknesses ranging from ~0.8 to 3.9 nm. Our calculations revealed features in the Raman spectra of the films that were absent in the bulk spectra. Out of the seven Raman-active modes associated with bulk STO, the frequencies of five modes (2E<sub>g,</sub> A<sub>1g</sub>, B<sub>2g</sub>, and B<sub>1g</sub>) decreased as the film thickness increased, while the low-frequency B<sub>2g</sub> and higher-frequency E<sub>g</sub> modes frequencies increased. The modes in the films exhibited vibrations with different amplitudes in the central or surface parts of the films compared to the bulk, resulting in frequency shifts. Some peaks related to bulk vibrations were too weak (compared to the new modes related to films) to distinguish in the Raman spectra. However, as the film thickness increased, the Raman modes approached the frequencies of the bulk, and their intensities became higher, making them more noticeable in the Raman spectrum. Our results could help to explain inconsistencies in the experimental data for thin STO films, providing insights into the behavior of Raman modes and their relationship with film thickness. |
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| last_indexed | 2024-03-10T22:31:20Z |
| publishDate | 2023-09-01 |
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| spelling | doaj.art-af7ec7dcf42d4d3db8503d1703e30c392023-11-19T11:44:22ZengMDPI AGMaterials1996-19442023-09-011618620710.3390/ma16186207Modeling of the Lattice Dynamics in Strontium Titanate Films of Various Thicknesses: Raman Scattering StudiesVeera Krasnenko0Alexander Platonenko1Aleksandr Liivand2Leonid L. Rusevich3Yuri A. Mastrikov4Guntars Zvejnieks5Maksim Sokolov6Eugene A. Kotomin7Institute of Physics, University of Tartu, 50411 Tartu, EstoniaInstitute of Solid State Physics, University of Latvia, LV-1586 Riga, LatviaInstitute of Physics, University of Tartu, 50411 Tartu, EstoniaInstitute of Solid State Physics, University of Latvia, LV-1586 Riga, LatviaInstitute of Solid State Physics, University of Latvia, LV-1586 Riga, LatviaInstitute of Solid State Physics, University of Latvia, LV-1586 Riga, LatviaTheoretical Inorganic Chemistry, University of Duisburg-Essen, 45141 Essen, GermanyInstitute of Solid State Physics, University of Latvia, LV-1586 Riga, LatviaWhile the bulk strontium titanate (STO) crystal characteristics are relatively well known, ultrathin perovskites’ nanostructure, chemical composition, and crystallinity are quite complex and challenging to understand in detail. In our study, the DFT methods were used for modelling the Raman spectra of the STO bulk (space group I4/mcm) and 5–21-layer thin films (layer group p4/mbm) in tetragonal phase with different thicknesses ranging from ~0.8 to 3.9 nm. Our calculations revealed features in the Raman spectra of the films that were absent in the bulk spectra. Out of the seven Raman-active modes associated with bulk STO, the frequencies of five modes (2E<sub>g,</sub> A<sub>1g</sub>, B<sub>2g</sub>, and B<sub>1g</sub>) decreased as the film thickness increased, while the low-frequency B<sub>2g</sub> and higher-frequency E<sub>g</sub> modes frequencies increased. The modes in the films exhibited vibrations with different amplitudes in the central or surface parts of the films compared to the bulk, resulting in frequency shifts. Some peaks related to bulk vibrations were too weak (compared to the new modes related to films) to distinguish in the Raman spectra. However, as the film thickness increased, the Raman modes approached the frequencies of the bulk, and their intensities became higher, making them more noticeable in the Raman spectrum. Our results could help to explain inconsistencies in the experimental data for thin STO films, providing insights into the behavior of Raman modes and their relationship with film thickness.https://www.mdpi.com/1996-1944/16/18/6207STOultrathin filmsRaman calculationsDFTdependence on thickness |
| spellingShingle | Veera Krasnenko Alexander Platonenko Aleksandr Liivand Leonid L. Rusevich Yuri A. Mastrikov Guntars Zvejnieks Maksim Sokolov Eugene A. Kotomin Modeling of the Lattice Dynamics in Strontium Titanate Films of Various Thicknesses: Raman Scattering Studies Materials STO ultrathin films Raman calculations DFT dependence on thickness |
| title | Modeling of the Lattice Dynamics in Strontium Titanate Films of Various Thicknesses: Raman Scattering Studies |
| title_full | Modeling of the Lattice Dynamics in Strontium Titanate Films of Various Thicknesses: Raman Scattering Studies |
| title_fullStr | Modeling of the Lattice Dynamics in Strontium Titanate Films of Various Thicknesses: Raman Scattering Studies |
| title_full_unstemmed | Modeling of the Lattice Dynamics in Strontium Titanate Films of Various Thicknesses: Raman Scattering Studies |
| title_short | Modeling of the Lattice Dynamics in Strontium Titanate Films of Various Thicknesses: Raman Scattering Studies |
| title_sort | modeling of the lattice dynamics in strontium titanate films of various thicknesses raman scattering studies |
| topic | STO ultrathin films Raman calculations DFT dependence on thickness |
| url | https://www.mdpi.com/1996-1944/16/18/6207 |
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