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. 
David B. Lioi, David J. Gosztola, Gary P. Wiederrecht, Goran   Karapetrov
cond-mat.str-el cond-mat.mes-hall