Tuning the electron–phonon interaction via exploring the interrelation between Urbach energy and fano-type asymmetric raman line shape in GO-hBN nanocomposites

Abstract

Hexagonal boron nitride (hBN), having an in-plane hexagonal structure in the sp2 arrangement of atoms, proclaims structural similarity with graphene with only a small lattice mismatch. Despite having nearly identical atomic arrangements and exhibiting almost identical properties, the electronic structures of the two materials are fundamentally different. Considering the aforementioned condition, a new hybrid material with enhanced properties can be evolved by combining both materials. This experiment involves liquid phase exfoliation of hBN and two-dimensional nanocomposites of GO-hBN with varying hBN and graphene oxide (GO) ratios. The optical and vibrational studies conducted using UV–vis absorption and Raman spectroscopic analysis report the tuning of electron–phonon interaction (EPI) in the GO-hBN nanocomposite as a function of GO content (%). This interaction depends on disorder-induced electronic and vibrational modifications addressed by Urbach energy (E u ) and asymmetry parameter (q), respectively. The EPI contribution to the induced disorders estimated from UV–vis absorption spectra is represented as EPI strength (E e–p ) and its impact observed in Raman phonon modes is quantified as an asymmetry parameter (q). The inverse of the asymmetry parameter is related to E e–p , as E e–p ∼ 1/|q|. Here in this article, a linear relationship has been established between E u and the proportional parameter (k), where k is determined as the ratio of the intensity of specific Raman mode (I) and q 2, explaining the disorders’ effect on Raman line shape. Thus a correlation between Urbach energy and the asymmetry parameter of Raman mode confirms the tuning of EPI with GO content (%) in GO-hBN nanocomposite.

Unveiling Electron–Phonon Interaction That Influences the Photoluminescence Properties of Cs2NaxAg1–xBiCl6 Mixed Halide Double Perovskites

“…Figure 2(b) also represents the variation of E u with changing Ag/Na concentrations, which is an indication of rising disorder of phonon states in these mixed compounds. Further, an estimate of the electron−phonon interaction strength (E e−p ) comes from E u using the relation 30 =…”

“…Figure (b) also represents the variation of E u with changing Ag/Na concentrations, which is an indication of rising disorder of phonon states in these mixed compounds. Further, an estimate of the electron–phonon interaction strength ( E e–p ) comes from E u using the relation E normale − normalp = 2 E u 3 K B T . Thus, a higher Urbach energy implies stronger electron–phonon interaction and hence should contribute heavily toward the formation of deep trap states, which in turn would result in enhanced PL properties.…”

“…When there is significant electron–phonon coupling in a given composition, such LO phonon modes are affected to a greater extent than the other modes. Thus, fitting the Breit–Wiger–Fano function to the A 1g Raman line shape, we obtain the estimate of asymmetry parameter, q , and by extension, the electron–phonon coupling strength, E e–p ∝ 1/| q |. As depicted in Figure (a), 1/| q | increases with an increase in Na concentration, reaching a maximum for 75% Na composition.…”