Theoretical and experimental investigation of vacancy-based doping of monolayer MoS${}_2$ on oxide

Abstract

Monolayer transition metal dichalcogenides are novel, gapped two-dimensional materials. Toward device applications, we consider MoS${}_2$ layers on dielectrics, in particular in this work, the effect of vacancies on the electronic structure. In density-functional based simulations, we consider the effects of near-interface O vacancies in the oxide slab, and Mo or S vacancies in the MoS${}_2$ layer. Band structures and atom-projected densities of states for each system and with differing oxide terminations were calculated, as well as those for the defect-free MoS${}_2$-dielectrics system and for isolated dielectric layers for reference. Among our results, we find that with O vacancies, both the Hf-terminated HfO${}_2$-MoS${}_2$ system, and the O-terminated and H-passivated Al${}_2$O${}_3$-MoS${}_2$ systems appear metallic due to doping of the oxide slab followed by electron transfer into the MoS${}_2$, in manner analogous to modulation doping. The n-type doping of monolayer MoS${}_2$ by high-k oxides with oxygen vacancies then is experimentally demonstrated by electrically and spectroscopically characterizing back-gated monolayer MoS${}_2$ field effect transistors encapsulated by oxygen deficient alumina and hafnia.

Updated author list to reflect journal version

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• Large enhancement of infrared absorption due to trimer comprised of doping-N and S-S divacancies in the imperfect monolayer MoS2: A first-principles study