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Abstract-Photoluminescence and X-ray diffraction are used to investigate 2H and 3R polytypes of MoS2 layered crystals intercalated with Cl2 molecules. The spectral structure of the observed bound excitons emission is individual for each polytype, that can be used for unambiguous identification of the 2H and 3R polytypes. The DFT band structure calculations have been done for three molecular layers of 2H-MoS2 and 3R-MoS2 polytypes without and with intercalation of Cl2 molecules. The spectroscopic experimental results confirmed theoretical calculations performed for both cases and it has been demonstrated that halogen intercalation completely changes the local band structure of 2H-and 3R-MoS2 polytypes.

A systematic optical characterization of transition metal dichalcogenide layered crystals grown by chemical vapour transport method as well as of natural molybdenite were carried out by using piezoreflectance (PzR) measurements. From a detailed lineshape fit of the room-temperature PzR spectra over an energy range from 1.6 to 5.0 eV, the energies of the band-edge excitonic and higher lying interband direct transitions were determined accurately. The possible assignments of the different origins of excitonic transitions are discussed. The near direct band edge A and B excitonic transitions detected in PzR spectra show a linear red-shift with the temperature increasing up to 525 K. The values of temperature-dependent energies of the excitonic transitions A and B are evaluated and discussed.