Environmental effects on the electronic states of MoS2 flakes probed by micro-ARPES

Abstract

A spatially resolved angle-resolved photoelectron spectroscopy investigation at the micron scale reveals the effects of the external environment on exfoliated MoS₂ multilayers. The electronic band dispersion and related parameters were measured on MoS₂ samples that were exfoliated and transferred in a controlled air-free atmosphere. Notably, these samples exhibited a more defined band structure and a higher spectral density of states compared to those prepared and transferred in air. In the latter case, surface contamination resulted in band broadening, particularly in the density of states linked to out-of-plane orbitals in the low binding energy region near the valence band maximum. Slight p-doping is also observed for the non-protected sample, which can be associated with tiny effects of ambient oxygen during transport. These findings underscore the necessity of air-protected exfoliation and transfer to accurately capture the fundamental properties of transition metal dichalcogenides.