The effect of temperature and excitation energy on Raman scattering in bulkHfS2.

Raman scattering (RS) in bulk hafnium disulfide (HfS2) is investigated as a function of temperature (5 K - 350 K) with polarization resolution and excitation of several laser energies. An unexpected temperature dependence of the energies of the main Raman-active (A1gand E) modes with the temperature-induced blueshift in the low-temperature limit is observed. The low-temperature quenching of a mode(134 cm) and the emergence of a new mode at approx. 184 cm, labeled, is reported. The optical anisotropy of the RS inHfS2is also reported, which is highly susceptible to the excitation energy. The apparent quenching of the A1gmode at = 5 K and of the Emode at= 300 K in the RS spectrum excited with 3.06 eV excitation is also observed. We discuss the results in the context of possible resonant character of light-phonon interactions. Analyzed is also a possible effect of the iodine molecules intercalated in the van der Waals gaps between neighboringHfS2layers, which inevitably result from the growth procedure.