Effect of dimensionality on the excitation wavelength dependence of the Fano-Raman line-shape: a brief review

The already existing heterogeneity in nanomaterials makes it an intriguing yet complex system to study size effect vis-à-vis other external perturbations and thereby local modifications at the nanoscale, thus demanding an improved tool and analysis for the choice of study. The analysis of existential subtle perturbations and interactions in a wide class of materials using Raman spectromicroscopy has proved to be of utmost importance, and various phenomena such as quantum confinement and its interplay with Fano resonance have already been investigated in nanomaterials, including the role of various perturbations such as temperature, pressure, doping, bias, and excitation wavelength on Raman spectral line shape parameters. Amongst different perturbations that cause a change in the spectral profile of Fano resonance, the gray area of wavelength dependence of Fano Raman line shape profiles has been least analysed in the literature. Moreover, the true signature of Fano resonance in nanoscaled systems, which is the wavelength dependence of Fano interaction, remains the least discussed. This review summarises the wavelength dependent correlation of Fano resonance and its effect on the Raman spectral line-shape parameters in some bulk materials, nanomaterials, and molecular systems involving heavily doped p-type crystalline silicon, 2-D MoS₂, graphene, WS₂, single walled carbon nanotubes, etc. A brief overview of Fano resonance in metamaterials and photonic systems is also provided.