Raman scattering and disorder effect in Cu₂ZnSnS₄

Abstract

The Raman spectra of surface regions of bulk Cu2ZnSnS4 (CZTS) samples with different Cu and Zn cation content were obtained and the differences in the spectra are attributed to statistical disorder effects in the cation sublattice. This disorder in the Cu and Zn sublattices may initiate a change of the crystal symmetry from kesterite‐type $({I\bar 4})$ to $({I\bar 42m})$ space group. The investigated CZTS crystals grown at high temperature are characterised by the co‐existence of regions with different composition ratio of Cu/(Zn + Sn) which results in kesterite and disordered kesterite phases. The presence of a disordered phase with ${I\bar 42m}$ symmetry is reflected in the appearance of a dominant broadened A‐symmetry peak at lower frequency than the peak of the main A‐symmetry kesterite mode at 337 cm–1. We suppose that due to a small energy barrier between these phases the transition from one phase to the other can be stimulated by optical excitation of Cu2ZnSnS4. The analysis of the Raman spectra measured under different excitation conditions has allowed obtaining first (to our knowledge) experimental evidence of the existence of such optically induced structural transition in CZTS. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Non-stoichiometry effect and disorder in Cu2ZnSnS4 thin films obtained by flash evaporation: Raman scattering investigation

“…The problem of non-stoichiometry in crystalline CZTS samples obtained by Bridgman method and solid-state reaction of pure elements has been studied by means of Raman spectroscopy in our previous reports [10][11][12]. This issue was also discussed for CZTS films grown by pneumatic spray pyrolysis in [13].…”

A low-temperature order-disorder transition in Cu2ZnSnS4 thin films

“…13 Beside this, in the 532 nm spectrum, fitting for VF revealed a small peak at 332 cm À1 . This has been tentatively attributed to Cu/Zn disorder, 17,18 but quantitative analysis is difficult because of the overlap and variable asymmetry of the dominating A mode at $339 cm À1 . In the 785 nm spectra, the differences between VS and VF are more dramatic.…”

The synthesis and characterization of Cu2ZnSnS4 thin films from melt reactions using xanthate precursors

“…The p-XRD data show that the films prepared at 400-450°C are KS-CZTS too, and the downshifted peak is due to disorder in Cu and Zn atoms in the sublattice. This is because the Cu and Zn atoms have a similar size and the difference between binding energy of the cations in the sublattice is small [65,66].…”