Theoretical realization of half-metallicity in two-dimensional monolayered molybdenum dinitride by Mo vacancy tuning

In experiment, defect-doping has been an efficient method to engineer the properties of materials. Motivated by the experimental synthesis of bulk MoN2 and theoretical exfoliation of two-dimensional monolayered counterpart, here we explore the possibility of realization of half-metallicity in T-type monolayered MoN2 by introducing vacancies on Mo sites via density-functional calculations. The results show that, once vacancies is introduced on Mo sites, T-type monolayered MoN2 would transfer from semiconductor to half-metal, and the half-metallicity is robust in the whole vacancy content range employed in this work. Besides, the half-metallicity is insensitive to N vacancies. Further study reveals that the half-metallicity is originated from the magnetic state on N sites. For the metastable H-type monolayered MoN2, it would also turn into half-metal, however, the vacancy rate should be beyond 25%. Such a relative large rate is due to the metallic property in vacancy-free H-type MoN2. Based on this work, we think that introducing vacancies on metal sites in nitrogen rich metal nitrides perhaps is a practicable way to search for half-metals.