The effect of temperature and excitation energy on Raman scattering in bulk HfS${}_2$

Abstract

Raman scattering (RS) in bulk hafnium disulfide (HfS${}_2$) 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${}_{\text{1g}}$ and E${}_{\text{g}}$) modes with the temperature-induced blueshift in the low-temperature limit is observed. The low-temperature quenching of a mode $\ddot{I}{‰}_1$ (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 HfS${}_2$ is also reported, which is highly susceptible to the excitation energy. The apparent quenching of the A${}_{\text{1g}}$ mode at $T$=5 K and of the E${}_{\text{g}}$ 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 HfS${}_2$ layers, which inevitably result from the growth procedure.

9 pages, 7 figures +SI