First-principles study on charged vacancies in MoS2

Charged vacancies of MoS2 are theoretically studied based on the first-principles calculation. The results for the freestanding single-layer MoS2 show that almost all of vacancies are more stable when they are more negatively charged. Lager vacancies can become high negative charge states. Formation energies of larger vacancies also more drastically change with the Fermi energy variation. The anion vacancies are easily formed. By the comparison with the results for vacancies of hexagonal boron nitride (h-BN), it is found that some special features for vacancies of MoS2. These are thought to come from the rather strong ionic bonding nature of MoS2. Supporting effects on vacancies are also theoretically studied. Vacancy formation is generally more suppressed for the supported cases than the freestanding case in non-negatively-charged conditions. It is suggested that MoS2 should be processed in the S-rich and non-negatively-charged conditions to prevent the formation of vacancies. It is also suggested that the choice of supporting substrate is important to process MoS2 and to obtain better quality electronic devices. (C) 2018 The Japan Society of Applied Physics