Quantifying the Short-Range Order in Amorphous Silicon by Raman Scattering

Abstract

Quantification of the short-range order in amorphous silicon has been formulized using Raman scattering by taking into account established frameworks for studying the spectral line-shape and size dependent Raman peak shift. A theoretical line-shape function has been proposed for representing the observed Raman scattering spectrum from amorphous-Si-based on modified phonon confinement model framework. While analyzing modified phonon confinement model, the term "confinement size" used in the context of nanocrystalline Si was found analogous to the short-range order distance in a-Si thus enabling one to quantify the same using Raman scattering. Additionally, an empirical formula has been proposed using bond polarizability model for estimating the short-range order making one capable to quantify the distance of short-range order by looking at the Raman peak position alone. Both the proposals have been validated using three different data sets reported by three different research groups from a-Si samples prepared by three different methods making the analysis universal.

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

“…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]. Figure 3a clearly shows that the Raman line shape becomes more and more asymmetry when the absolute value of q reduces (due to increase in Fano coupling).…”

“…Raman scattering [1,2], since its discovery in 1928, has now been established as a spectroscopic technique [3][4][5][6] having many applications in different fields of science, engineering and technology [7,8]. Beyond identification of bond modes, a Raman spectrum is capable of investigating several materials' properties if analysed under appropriate framework.…”

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

“…This can be seen in the Figure S3 which compares the line shape obtained for a 2-nm-sized cluster using the two models. It is clear that PCM is applicable within the size domains where the crystallinity is preserved up to a F I G U R E 1 (a) Variation of the Lorentzian weighing function, F(q), as a function of wave vector for 1.8-(blue curve) and 2-nm (red curve) clusters as compared with Gaussian (inset) and (b) theoretical Raman line shapes generated using direct matrix method and bond polarization model (DMM-BPM) model for sizes 1.0, 1.5, and 2.0 nm for a Γ value of 500 cm −1 F I G U R E 2 Raman spectra of amorphous Si (a-Si) of samples S1, S2, and S3 (partly adapted with permission from Yogi et al, [58] copyright [2018] American Chemical Society): discrete points show experimentally obtained data of Raman spectra, and solid lines show the theoretical fitting by direct matrix method and bond polarization model (DMM-BPM) model few nanometers and works for nanomaterials having sizes comparable with the corresponding Bohr exciton radius (5 nm for Si). [65][66][67] For smaller sizes, the PCM predicts an undefined line shape (red curve, Figure S3).…”

Si nanocrystal solution with stability for one year

“…The size of the crystalline region involved in the SiNC was estimated using an empirical equation relating Raman shi (n) and crystalline size (D) of spherical SiNC (Fig. S1 †): [79][80][81] n ¼ n 0 À 47.41(0.543/D) 1.44 (1)…”