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| Auteurs principaux: | , , , , |
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| Format: | Preprint |
| Publié: |
2025
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| Accès en ligne: | https://arxiv.org/abs/2507.14763 |
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| _version_ | 1866911118368178176 |
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| author | Boy, J. Mitdank, R. Popp, A. Galazka, Z. Fischer, S. F. |
| author_facet | Boy, J. Mitdank, R. Popp, A. Galazka, Z. Fischer, S. F. |
| contents | Phonon drag may be harnessed for thermoelectric generators and devices. Here, we demonstrate the geometric control of the phonon-drag contribution to the thermopower. In nanometer-thin electrically conducting $β$-Ga$_2$O$_3$ films homoepitaxially-grown on insulating substrates it is enhanced from -0,4 mV/K to up to -3 mV/K at 100 K by choice of the film thickness. Analysis of the temperature-dependent Seebeck coefficients reveal that a crossover from three-dimensional to quasi-two-dimensional electron-phonon interaction occurs for film thicknesses below 75~nm. The ratio of phonon-phonon to electron-phonon relaxation times in these confined structures is $10$ times larger than that of bulk. Generally the phonon drag can be tuned depending on the relations between the phonon-drag interaction length $λ_\text{PD}$, the phonon mean free path $λ$ and the film thickness $d$. Phonon drag can be enhanced for $λ_\text{PD}\ggλ>d$. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2507_14763 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Enhanced phonon-drag by nanoscale design of homoepitaxial \hbox{$β$-Ga$_2$O$_3$} Boy, J. Mitdank, R. Popp, A. Galazka, Z. Fischer, S. F. Mesoscale and Nanoscale Physics Materials Science Phonon drag may be harnessed for thermoelectric generators and devices. Here, we demonstrate the geometric control of the phonon-drag contribution to the thermopower. In nanometer-thin electrically conducting $β$-Ga$_2$O$_3$ films homoepitaxially-grown on insulating substrates it is enhanced from -0,4 mV/K to up to -3 mV/K at 100 K by choice of the film thickness. Analysis of the temperature-dependent Seebeck coefficients reveal that a crossover from three-dimensional to quasi-two-dimensional electron-phonon interaction occurs for film thicknesses below 75~nm. The ratio of phonon-phonon to electron-phonon relaxation times in these confined structures is $10$ times larger than that of bulk. Generally the phonon drag can be tuned depending on the relations between the phonon-drag interaction length $λ_\text{PD}$, the phonon mean free path $λ$ and the film thickness $d$. Phonon drag can be enhanced for $λ_\text{PD}\ggλ>d$. |
| title | Enhanced phonon-drag by nanoscale design of homoepitaxial \hbox{$β$-Ga$_2$O$_3$} |
| topic | Mesoscale and Nanoscale Physics Materials Science |
| url | https://arxiv.org/abs/2507.14763 |