Generalisation of phonon confinement model for interpretation of Raman line-shape from nano-silicon

Abstract

A comparative analysis of two Raman line-shape functions has been carried out to validate the true representation of experimentally observed Raman scattering data for semiconducting nanomaterials. A modified form of already existing phonon confinement model incorporates two basic considerations, phonon momentum conservation and shift in zone centre phonon frequency. After incorporation of the above mentioned two factors, a rather symmetric Raman line-shape is generated which is in contrary to the usual asymmetric Raman line-shapes obtained from nanostructured semiconductor. By fitting an experimentally observed Raman scattering data from silicon nanostructures, prepared by metal induced etching, it can be established that the Raman line-shape obtained within the framework of phonon confinement model is a true representative Raman line-shape of sufficiently low dimensions semiconductors.

Effect of annealing temperature on thermo‐diffusional boron doping of silicon nanowire arrays probed by Raman spectroscopy

“…[ 32,33,35,36 ] Note that in this case, the observed distortions in Raman spectra correspond to theoretical considerations that phonon confinement reveals itself in the structures with a diameter less that 10–20 nm. [ 23–29,31–34 ] We do not observe any maximum red shift within the chosen spectral resolution or a broader half‐width at the lower wavenumber side of the Raman spectra of as‐prepared and thermally annealed SiNWs (Figure 2a) as could be expected for small‐diameter nanowires. [ 31 ] We also have a good fit by the Fano‐resonance model (Equation ) as shown in Figure 3 and Figure 5.…”

“…[ 23–29,31–34 ] We do not observe any maximum red shift within the chosen spectral resolution or a broader half‐width at the lower wavenumber side of the Raman spectra of as‐prepared and thermally annealed SiNWs (Figure 2a) as could be expected for small‐diameter nanowires. [ 31 ] We also have a good fit by the Fano‐resonance model (Equation ) as shown in Figure 3 and Figure 5. Thus, we consider it to match the chosen method of thermo‐diffusional doping of SiNWs after their fabrication from low‐doped p ‐type c‐Si by MACE.…”

“…Because the Raman line shape can be modified by phonon confinement, [ 22–36 ] one should be scrupulous about the possible impact of phonon confinement to the estimations of the FCC concentration in SiNWs. MACE formation of SiNW arrays on highly boron‐doped c‐Si substrates leads to the narrowing of nanowire diameter and additional nanowire porosity that results in a distortion of the lower wavenumber side of Fano‐resonance line.…”

Effect of some physical perturbations and their interplay on Raman spectral line shapes in silicon: A brief review

“…Unlike for c-Si, in the case of SiNSs, the abovementioned k = 0 selection rule gets relaxed, first reported by Richter et al [71] and Campbell and Fauchet [72] and later on validated by many others. [37,41,66,[73][74][75][76][77][78][79][80] As a consequence of momentum relaxation, phonons other than the zone centered ones, governed by phonon dispersion relation, also contribute in a crystallite of finite dimension. This results in a change in the first order Raman spectrum, which is typically Lorentzian for crystalline materials.…”

Predicting Raman line shapes from amorphous silicon clusters for estimating short‐range order

“…It has become one of the essential techniques for nanomaterials which helps in investigating properties like quantum confinement effect, electron–phonon interaction, [ 29 ] and anharmonic effects at microscopic levels that otherwise is not possible. [ 30–33 ] A typical Raman spectrum from a solid, being sensitive of the phonons' behavior, may change its whole line shape in response to any perturbation in the system and not just only the peak position or width. The overall spectral line shape, and thus the Raman spectrum, can be predicted if one knows the phonons behavior in a solid.…”