Growth, characterization, and Raman spectra of the 1T phases of TiTe₂, TiSe₂, and TiS₂

High-quality large 1T phase of TiX 2 (X = Te, Se, and S) single crystals have been grown by chemical vapor transport using iodine as a transport agent. The samples are characterized by compositional and structural analyses, and their properties are investigated by Raman spectroscopy. Several phonon modes have been observed, including the widely reported A 1g and Eg modes, the rarely reported Eu mode (∼183 cm−1 for TiTe2, and ∼185 cm−1 for TiS2), and even the unexpected K mode (∼85 cm−1) of TiTe2. Most phonons harden with the decrease of temperature, except that the K mode of TiTe2 and the Eu and “A 2u /Sh” modes of TiS2 soften with the decrease of temperature. In addition, we also found phonon changes in TiSe2 that may be related to charge density wave phase transition. Our results on TiX 2 phonons will help to understand their charge density wave and superconductivity.