The microstructure of CuInS 2 ͑CIS 2 ) polycrystalline films deposited onto Mo-coated glass has been analyzed by Raman scattering, Auger electron spectroscopy ͑AES͒, transmission electron microscopy, and x-ray diffraction techniques. Samples were obtained by a coevaporation procedure that allows different Cu-to-In composition ratios ͑from Cu-rich to Cu-poor films͒. Films were grown at different temperatures between 370 and 520°C. The combination of micro-Raman and AES techniques onto Ar ϩ -sputtered samples has allowed us to identify the main secondary phases from Cu-poor films such as CuIn 5 S 8 ͑at the central region of the layer͒ and MoS 2 ͑at the CIS 2 /Mo interface͒. For Cu-rich films, secondary phases are CuS at the surface of as-grown layers and MoS 2 at the CIS 2 /Mo interface. The lower intensity of the MoS 2 modes from the Raman spectra measured at these samples suggests excess Cu to inhibit MoS 2 interface formation. Decreasing the temperature of deposition to 420°C leads to an inhibition in observing these secondary phases. This inhibition is also accompanied by a significant broadening and blueshift of the main A 1 Raman mode from CIS 2 , as well as by an increase in the contribution of an additional mode at about 305 cm Ϫ1 . The experimental data suggest that these effects are related to a decrease in structural quality of the CIS 2 films obtained under low-temperature deposition conditions, which are likely connected to the inhibition in the measured spectra of secondary-phase vibrational modes.