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Photon-Induced Selenium Vacancies in TiSe2

TiSe2 is a member of transition metal dichalcogenide family of layered van-der-Waals materials that exhibits some distinctive electronic and optical properties. Here, we perform Raman spectroscopy studies on single crystal TiSe2 to investigate photon-induced defects associated with formation of selenium vacancies. Two additional Eg phonon peaks are observed in the laser-irradiated regions, consistent with Raman spectra of selenium deficient TiSe2. Temperature dependent studies of the threshold laser intensity necessary to form selenium vacancies show that there is a linear dependence. We extract the relevant activation energy for selenium vacancy nucleation. The impact of these results on the properties of strongly correlated electron states in TiSe2 are discussed.