Fano Scattering: Manifestation of Acoustic Phonons at the Nanoscale

Abstract

Size-dependent asymmetric low-frequency Raman line shapes have been observed from silicon (Si) nanostructures (NSs) due to a quantum confinement effect. The acoustic phonons in Si NSs interact with an intraband quasi-continuum to give rise to Fano interaction in the low-frequency range. The experimental asymmetric Raman line shape has been explained by developing a theoretical model that incorporates the quantum-confined phonons interacting with an intraband quasi-continuum available in Si NSs as a result of discretization of energy levels with unequal separation. We discover that a phenomenon similar to Brillouin scattering is possible at the nanoscale in the low-frequency regime and thus may be called "Fano scattering" in general. A method has been proposed to extract information about nonradiative transitions from the Fano scattering data where these nonradiative transitions are involved as an intraband quasi-continuum in modulation with discrete acoustic phonons.

Analysis of heavily boron-doped diamond Raman spectrum

“…Fano effect, conformably with the ZCP line [20]. This analysis is also analogous to Yogi et al work on silicon nanostructures who report the observation of a size-dependent position asymmetric peak due to acoustic phonons by Raman spectroscopy due to the quantum confinement effect and their interaction with intraband quasi-continuum [33].…”

Brain Tumour Detection and Grading Using Raman Scattering: Analogy from Semiconductors for Solving Biological Problem

“…The simplified general equation for universal Raman line shape can be represented by Eq. 1 below: representing a donor-type discrete-continuum Fano interference [14,[47][48][49]51] for a given crystallite size of 3 nm. The obtained theoretical line shapes are broad and asymmetric (as compared to crystalline Si counterpart which is sharp and symmetric [4,6,50]) in nature as a consequence of the classic discrete-continuum (Fano-) interaction [52].…”

“…Mode identification can be done by indexing the Raman peak positions but it may contain lot more information than simple chemical bonds energies which may also be investigated using IR spectroscopy, of course with certain limitations. Beyond the peak position of a Raman peak, the overall line shape of the spectrum is equally important as it may reveal several important physical phenomena taking place at microscopic level like quantum confinement or size effect, electron-phonon effect, fantum effect etc [9][10][11][12][13][14][15][16][17]. Apart from direct evidences, as a consequence of Raman line-shape's sensitivity towards external conditions, perturbations induced by temperature, pressure etc also can be investigated using classical and advanced Raman techniques [18][19][20][21][22].…”

Expressing Raman Spectral Details Through Raman Parameter Information Diagram (RAPID)

“…Raman spectroscopy [1][2][3][4][5][6][7][8][9][10][11] is an unavoidable tool for an experimental scientist, associated with industry and/or academia, especially for ones who are involved in materials' research as this is one of the most widely used characterization techniques because of its certain advantages. Various information pertaining to a material characteristics is reflected and stored in the form of a Raman spectrum, consisting of one or more peaks, recorded after Raman scattering has taken place.…”