Origin of Mechanical and Dielectric Losses from Two-Level Systems in Amorphous Silicon
| Autor: | Frances Hellman, Manel Molina-Ruiz, Jonathan L. DuBois, Xiao Liu, H. C. Jacks, Yaniv Rosen, T. H. Metcalf, M. R. Abernathy |
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| Jazyk: | angličtina |
| Rok vydání: | 2020 |
| Předmět: |
Amorphous silicon
Electromagnetic field Condensed Matter - Materials Science Materials science Physics and Astronomy (miscellaneous) Condensed matter physics Phonon Materials Science (cond-mat.mtrl-sci) FOS: Physical sciences 02 engineering and technology 021001 nanoscience & nanotechnology Coupling (probability) 01 natural sciences Amorphous solid Dipole chemistry.chemical_compound Condensed Matter::Materials Science chemistry 0103 physical sciences General Materials Science Dielectric loss Thin film 010306 general physics 0210 nano-technology |
| Popis: | Amorphous silicon contains tunneling two-level systems, which are the dominant energy loss mechanisms for amorphous solids at low temperatures. These two-level systems affect both mechanical and electromagnetic oscillators and are believed to produce thermal and electromagnetic noise and energy loss. However, it is unclear whether the two-level systems that dominate mechanical and dielectric losses are the same; the former relies on phonon-TLS coupling, with an elastic field coupling constant, $\gamma$, while the latter depends on a TLS dipole moment, $p_0$, which couples to the electromagnetic field. Mechanical and dielectric loss measurements as well as structural characterization were performed on amorphous silicon thin films grown by electron beam deposition with a range of growth parameters. Samples grown at 425 $^{\circ}$C show a large reduction of mechanical loss (34 times) and a far smaller reduction of dielectric loss (2.3 times) compared to those grown at room temperature. Additionally, mechanical loss shows lower loss per unit volume for thicker films, while dielectric loss shows lower loss per unit volume for thinner films. Analysis of these results indicate that mechanical loss correlates with atomic density, while dielectric loss correlates with dangling bond density, suggesting a different origin for these two energy dissipation processes in amorphous silicon. Comment: 17 pages, 4 figures, 1 table |
| Databáze: | OpenAIRE |
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