Influence of quantum confinement on the electronic structure of the transition metal sulfide<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>T</mml:mi></mml:mrow></mml:math>S<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow/><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>

Abstract

Bulk MoS${}_{2}$, a prototypical layered transition-metal dichalcogenide, is an indirect band gap semiconductor. Reducing its slab thickness to a monolayer, MoS${}_{2}$ undergoes a transition to the direct band semiconductor. We support this experimental observation by first-principle calculations and show that quantum confinement in layered $d$-electron dichalcogenides results in tuning the electronic structure. We further studied the properties of related $T$S${}_{2}$ nanolayers ($T=$ W, Nb, Re) and show that the isotopological WS${}_{2}$ exhibits similar electronic properties, while NbS${}_{2}$ and ReS${}_{2}$ remain metallic independent of the slab thickness.