Interband Transitions in Monolayer and Few-Layer WSe2 Probed Using Photoexcited Charge Collection Spectroscopy.

Transition-metal dichalcogenides are currently under rigorous investigation because of their distinct layer-dependent physical properties originating from the corresponding evolution of the band structure. Here, we report the highly resolved probing of layer-dependent band structure evolution for WSe2 using photoexcited charge collection spectroscopy (PECCS). Monolayer, few-layer, and multilayer WSe2 can be probed in top-gate field-effect transistor platforms, and their interband transitions are efficiently observed. Our theoretical calculations show a great coincidence with the PECCS results, proving that the indirect Γ-K and Γ-Λ transitions as well as the direct K-K transition are clearly resolved in multilayer WSe2 by PECCS.