Probing lattice dynamics in ST12 phase germanium nanowires by Raman spectroscopy
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Date
2021-12-08
Authors
Raha, Sreyan
Srivastava, Divya
Biswas, Subhajit
Garcia-Gil, Adrià
Karttunen, Antii J.
Holmes, Justin D.
Singha, Achintya
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AIP Publishing
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Abstract
Germanium (Ge) plays a crucial role in setting up important functionalities for silicon-compatible photonics. Diamond cubic germanium is an extensively studied semiconductor, although its other exotic forms, like BC8, ST8, ST12 phases, may possess distinct electronic properties. We have fabricated stable ST12-Ge nanowires via a self-seeded bottom-up three phase growth in a confined supercritical toluene environment. Here, we report on the direct evidence of the presence of the ST12 phase by a combination of Raman spectroscopy and first-principles calculations using density functional theory (DFT). It is important to remark that the DFT calculation predicts all the Raman active optical phonon modes of the P 4321 structure, and it is in very good agreement with the experimental results. The phonon dynamics as a function of temperature is investigated through Raman measurements at temperatures varying from 80 to 300 K. First-order temperature coefficients for all the observed Raman modes are estimated from the linear temperature dependence of the phonon shifts. A complete set of isobaric Grüneisen parameters is reported for all Raman modes of ST12-Ge nanowire, and the values are lower compared to the same for Si, dc-Ge bulk, and Ge nanowire. These results have important implications for understanding thermal properties of ST12-Ge nanowire.
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In-situ integration , Density of states , High pressure , Amorphous silicon , Crystal structure , Ge , Anodes , Transitions , Nanocrystals , Parameters , First-principle calculations , Polymorphism , Nanowires , Lattice dynamics , Germanium , Raman spectroscopy , Density functional theory
Citation
Raha, S., Srivastava, D., Biswas, S., Garcia-Gil, A., Karttunen, A. J., Holmes, J. D. and Singha, A. (2021) 'Probing lattice dynamics in ST12 phase germanium nanowires by Raman spectroscopy', Applied Physics Letters, 119, (7 pp). doi: 10.1063/5.0066744
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Published under an exclusive license by AIP Publishing. This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in Appl. Phys. Lett. 119, 232105 (2021) and may be found at https://doi.org/10.1063/5.0066744