Isotopic Heft on the B Silent Mode in Ultra-Narrow Gallium Nitride Nanowires.

Author(s) Rodríguez-Fernández, C.; Almokhtar, M.; Ibarra-Hernández, W.; de Lima, M.Morais; Romero, A.H.; Asahi, H.; Cantarero, A.
Journal Nano Lett
Date Published 2018 Aug 08
Abstract

Wurtzite semiconductor compounds have two silent modes, B and B. A silent mode is a vibrational mode that carries neither a dipole moment nor Raman polarizability. Thus, they are forbidden in both infrared reflectivity and Raman spectroscopy. Astonishingly, we detected the B mode in high-quality, ultra-narrow GaN nanowires using resonant Raman scattering, although the B was not observed, and there is no immediate explanation for this asymmetric finding. The Raman experiments were performed using several laser lines from 647 to 325 nm; the latter is a wavelength in which Raman becomes resonant. Actually, we observed the B mode only in resonance, indicating that the appearance of this mode is related to Fröhlich electron-phonon interactions; i.e., a dipole moment emerging in the B silent mode may not be present in the B mode. To shed light onto the physical origin of these observations, we performed density functional theory calculations of the lattice dynamics in GaN. We performed a careful analysis of the different physical mechanisms that allow the forbidden mode to appear to explain the physics underlying the nonzero dipole moment in the B mode, and the reason why this dipole moment is not present in the B mode.

DOI 10.1021/acs.nanolett.8b01955
ISSN 1530-6992
Citation Rodríguez-Fernández C, Almokhtar M, Ibarra-Hernández W, de Lima MM, Romero AH, Asahi H, et al. Isotopic Heft on the B Silent Mode in Ultra-Narrow Gallium Nitride Nanowires. Nano Lett. 2018;18(8):5091-5097.

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