Effect of quantum confinement on electronic and dielectric properties of niobium dichalcogenides NbX2 (XÂ =Â S, Se, Te)

► Band structure remains metallic irrespective of quantum confinement effect. ► EELS for both E⊥c and E∥c shows red shift in energy as going from bulk to monolayer. ► The intensity of π(π+σ) plasmons peak increases (decreases) with decrease in number of layers. ► Interband transitions are mainly due to transition from chalcogens-p to Nb-d bands. ► Tunable dielectric properties of NbX2 can be useful for the applications in optoelectronic devices.