Thickness dependent Raman spectroscopy in 1T-TaS$_{2}$

Much attention has been paid recently to layered transition metal dichalcogenides (TMDs), which exhibit unique optical properties as their thickness is reduced from the bulk down to a monolayer. Here, we study Raman spectra of mono-and few-layered 1T-TaS$_{2}$, a metallic TMD, which is known to exhibit temperature-dependent commensurate and incommensurate charge density waves. We measure the low frequency Raman spectra of mechanically exfoliated 1T-TaS$_{2}$ on SiO$_{2}$ substrates with thicknesses ranging from 100 nm down to 1 nm. The room temperature Raman spectra exhibit numerous sharp peaks with frequencies below 100 cm$^{-1}$, which evolve with reducing thickness. Temperature and polarization dependence of the low frequency modes reveals the emergence of new in-plane and out-of-plane modes. Density functional theory calculations suggest the origin of these peaks to zone folding of the 1T-TaS$_{2}$ Brillouin zone. Acknowledgement: This work is based upon research supported by the National Science Foundation under Grant No. 0955625.