Vibrational and crystalline properties of polymorphic CuInC2 C S, Se chalcogenides

This paper deals with the analysis of the vibrational and crystalline properties of CuInC2 C S, Se chalcogenides. Experimentally, evidence on the coexistence in epitaxial layers of domains with different crystalline order corresponding to the equilibrium chalcopyrite CH and to CuAu CA has been obtained by cross section transmission electron microscopy and high resolution TEM HREM . Electron diffraction and HREM images give the crystalline relationship [1 10]CH II [100]CA and 112 CH II 011 CA, observing the existence of a 112 CH II 001 CA interphase bertween different ordered domains. The vibrational properties of these polytypes have been inverstigated by Raman scattering. Raman scattering, in conjunction with SCR, has allowed identifying the presence of additional bands in the Raman spectra with vibrational modes of the CA ordered phase. In order to interpret these spectra, a valence field force model has been developed to calculate the zone center vibrational modes of the CA structure for both CuInS2 and CuInSe2 compounds. The results of this calculation have led to the identification, in both cases, of the main additional band in the spectra with the total symmetric mode form the CuAu lattice. This identification is also supported by first principles frozen phonon calculations. Finally, the defect structure at the interphase boundaries betwen different polymorphic domains has also been investigate