The effect of temperature and excitation energy on Raman scattering in bulk HfS2

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 (A(1g) and E-g) modes with the temperature-induced blueshift in the low-temperature limit is observed. The low-temperature quenching of a mode omega(1) (134 cm(-1)) and the emergence of a new mode at approx. 184 cm(-1), labeled Z, is reported. The optical anisotropy of the RS in HfS2 is also reported, which is highly susceptible to the excitation energy. The apparent quenching of the A1g mode at T = 5 K and of the Eg mode at T = 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 neighboring HfS2 layers, which inevitably result from the growth procedure.