Temperature dependence of energies and broadening parameters of the band-edge excitons of single crystals

Abstract

We have measured the temperature dependence of the spectral features in the vicinity of direct band-edge excitonic transitions of single crystals from 25 to 300 K using piezoreflectance (PzR). From a detailed lineshape fit of the PzR spectra, the energies and broadening parameters of the A and B excitons have been determined accurately. The origin of these excitonic transitions is discussed. The transition energies and their splittings vary smoothly with the tungsten composition x, indicating that the natures of the direct band edges are similar for the compounds. In addition, the parameters that describe the temperature variation of the energies and broadening function of the excitonic transitions are evaluated and discussed.

Optical and Transport Properties of Ni-MoS2

“…The empirical expression is shown as below in Equation (2). consistency with similar results of reflection of the MoS2 as proposed by Ho et al [30]. Therefore, the temperature shift of excitonic-transition energies could be attributed to both the lattice variations and interactions with relevant acoustic and optical phonons.…”

Characterization of near band-edge properties of synthetic p-FeS2 iron pyrite from electrical and photoconductivity measurements

“…The obtained values of E g (0), S and together with those of Varshni fits are listed in Table 1. The values of fitting parameters which describe the temperature dependence of indirect gaps of FeS 2 [7,16,22], and interband transitions of other transition-metal sulfides MoS 2 [23], WS 2 [23], and ReS 2 [24] are also listed for comparison. The electron-phonon coupling constant S describing the temperature dependence of the transition energies of A 2 is comparable to that of the indirect gap E ind g (Ref.…”

“…This observation lends extra evidence that the A 2 feature is correlated to the band-to-band transition, but the A 1 feature is most likely related to an impurity or defect state to the conduction band. The defect or impurity center existing in the band gap of FeS 2 is temperature insensitive so that the temperature variation Table 1 Values of fitting parameters of the Varshni equation [20] and an expression proposed by O'Donnel and Chen [21] which describe the temperature dependence of the transition energies of FeS 2 The values of fitting parameters which describe the temperature dependence of indirect gaps of FeS 2 [7,16,22], and the interband transitions of other transition-metal sulfides MoS 2 [23], WS 2 [23], and ReS 2 [24] are listed for comparison. a This work.…”

Characterization of As2(Se1−xSx)3 series glass system

“…This observation lends experimental evidence that the As 2 (Se 1−x S x ) 3 series compounds are direct band-gap material in which the transition peak in each TR spectrum is closely matched with the absorption edge of the transmittance spectrum. This phenomenon is different from many other indirect crystals where the absorption edge is located at lower-energy side while the direct excitonic transitions are presented at higher-energy positions [24,25]. The transition feature in the TR spectrum of As 2 (Se 1−x S x ) 3 also shows an energy blue-shift behavior with the increase of sul- Fig.…”