Resonant Raman scattering of ZnS_xSe_1−x solid solutions: the role of S and Se electronic states

Abstract

A comprehensive Raman resonance scattering study of ZnSxSe1-x (ZnSSe) solid solutions over the whole compositional range (0 ≤ x ≤ 1) has been carried out using 325 and 455 nm excitation wavelengths. The Raman scattering intensities of LO ZnS-like and ZnSe-like phonon modes, corresponding to pure S and Se vibrations, respectively, are revealed to be significantly enhanced when excited with 325 nm excitation in the case of S vibrations, and with 455 nm in the case of Se vibrations. This behavior is explained by the interaction of the excitation photons with the corresponding S or Se electronic states in the conduction band, and further confirmed by first principles simulations. These findings advance the fundamental understanding of the coupling between the electronic transitions and photons in the case of Raman resonance effects, and provide inputs for further studies of lattice dynamics, especially in the case of chalcogenide materials. Additionally, the coexistence of modes corresponding to only S vibrations and only Se vibrations in the ZnSSe alloys makes these results applicable for the compositional assessment of ZnSSe compounds.

Advanced Raman Spectroscopy of Methylammonium Lead Iodide: Development of a Non-destructive Characterisation Methodology

“…This coupling of the 532 nm photons with the 2.4 eV band induces a selective enhancement of the peaks related to vibrations where these atoms are involved, while it should not take place at an excitation with 633 nm (1.9 eV). Similar effects have been reported for different materials such as Cu 2 ZnSnSe 4 40, MoS 2 41 and are explained in detail for the Zn(S, Se) system43.…”

“…Similar analyses of how parameters such as composition, degradation, process temperature, layer thickness, etc. affect the Raman spectra and correlate with optoelectronic properties and device performance have been performed extensively in other photovoltaics material systems such as Si49, CIGSSe24, CZTSSe4043. It has to be stressed, however, that a meaningful interpretation of these correlations always requires a careful calibration of the measured Raman parameter with the optoelectronic properties to be evaluated.…”

How small amounts of Ge modify the formation pathways and crystallization of kesterites

“…At the surface, Cu x Se is clearly detected with all three excitation wavelengths, 22 in agreement with the EDX and XRD analysis. At the back side, ZnSe is observed when using 488 nm excitation 23 together with Sn-Se phases, 24 and a very weak and broad band that is tentatively attributed to amorphous CZTSe. In any case, no evidences of Cu-Sn-Se phases are present, in agreement with the in-depth physical separation of Cu and Sn observed by EDX.…”

Raman scattering quantitative assessment of the anion composition ratio in Zn(O,S) layers for Cd-free chalcogenide-based solar cells

“…Raman scattering is a powerful nondestructive tool very sensitive to both the atomic composition and the crystal quality of the layers, and has already been reported for the quantitative composition analysis of chalcogenide semiconductors, including the assessment of the S/(S + Se) content ratio in sulfo-selenide alloys from the CIGS, CZTS and Zn(S,Se) systems. [9][10][11] Raman scattering analysis of Zn(O,S) solid solutions has already been reported in ref. [12][13][14][15].…”