Raman scattering in orthorhombic CuInS₂ nanocrystals

Abstract

We report the results of non‐resonant and resonant Raman scattering in orthorhombic nanocrystalline CuInS2 semiconductor, supported by density functional first principle lattice dynamics calculations. A larger number of dominant phonon modes in comparison with standard tetragonal CuInS2 phases is shown to be associated with peculiarities of cation sublattice ordering and is the “fingerprint” of the corresponding structural polymorph. Good overall agreement is found between theoretical and experimental phonon mode frequencies.

Ultra-small aqueous glutathione-capped Ag–In–Se quantum dots: luminescence and vibrational properties

“…Note, however, that in the case of non-stoichiometric Cu-In-S QDs, 52 the trend in A 1 /LO intensity ratio with l exc was opposite to the one observed for bulk or stoichiometric QD samples. 61 Based on this fact and the present dependence of the Raman spectra on l exc (Fig. 7), we can conclude that the Raman spectra of the strongly non-stoichiometric QDs are determined not only by the lattice structure but even more strongly by the details of the electronic band structure and concomitant resonances with l exc , as well as by the details of the electron-phonon coupling.…”

“…54 On the other hand, the heating-induced changes of the Raman spectra of AISe QDs are generally similar to those we previously observed for CuInS 2 , 52 and attributed to increased relative intensity of the highest-frequency LO modes, situated at 340-350 cm À1 for CuInS 2 (ref. 61) and, presumably, at 230-240 cm À1 for present AISe QDs. This assumption is in good qualitative agreement with the position of these modes obtained from the (only reported) experimental study of IR phonons in AgInSe 2 (ref.…”

“…This is contrary to related compounds like CuInS 2 and CuInSe 2 , 57-59 phonon spectra of which were addressed theoretically [60][61][62] and experimentally by Raman 57,58 and IR spectroscopies, 60 including QDs. 61 The strongest Raman active mode of tetragonal (chalcopyrite) CuInSe 2 is the A 1 -symmetry mode at 175 cm À1 , observed both in bulk samples 57,58 and QDs. 63 Besides, the so-called CuAu structural modication can exist in both CuInSe 2 and CuInS 2 , predominantly in Cu-poor samples, which has a characteristic A 1 mode at about 185 cm À1 .…”

Raman and Infrared Phonon Spectra of Novel Nonlinear Optical Materials PbGa2GeS6 and PbGa2GeSe6: Experiment and Theory

“…One can notice from Figure 2 a drastic difference in the relative peaks' intensities of several modes of PbGa 2 GeSe 6 at nonresonant (514 nm or 2.41 eV) and resonant (near-bandgap) excitation (671 nm or 1.85 eV). Based on numerous previous studies, including those of the authors, [14,19,20] such a difference is most likely related to the enhancement of the longitudinal optical (LO) modes in resonant conditions due to the Fröhlich electron-phonon interaction. However, as the calculation of the LO/TO splitting (where TO is the transversal optical phonon) for the compounds under study in this work is rather resource demanding, we also did not discuss in detail the experimental resonant effects related to the polar modes.…”

Crystal structure and vibrational properties of Cu2ZnSiSe4quaternary semiconductor

“…It is worth pointing out, that the calculated difference in the enthalpy of formation of kesterite and wurtzstannite polymorphs is rather small (2.4 kJ mol −1 ), so that the structure of CuZnSiSe could be very sensitive to growth conditions. Consequently, a high probability of coexistence of two polymorphs or even formation of new crystal structures has to be taken into account, as was recently established for CuZnSn(S,Se) and related ternary compounds .…”