Interaction of commensurate charge density waves with anionic point defects in electron beam irradiated 1T-TaSe2 and 1T-TaS2

Low dimensional transition metal dichalcogenides (MX2, M = transition metal e.g Nb, Mo, Ti X= chalcogen e.g S, Te, Se) are of great interest due to some of their unique properties including metal-insulator transitions and charge density waves (CDW) observed as a function of temperature, pressure, and doping. Here we report on the interaction of commensurate charge density waves and anionic point defects in 1T-TaSe2 and 1T-TaS2. By using atomic resolved high resolution transmission microscopy (HRTEM) we show the loss of CDW long range order as a result of the interaction with S and Se vacancies generated by the electron beam irradiation. We discuss the loss of long range order as a result of the interaction between the CDW and the Friedel oscillations arising from the point defects.