Resolving Deep Quantum-Well States in Atomically Thin 2H-MoTe₂ Flakes by Nanospot Angle-Resolved Photoemission Spectroscopy.

Abstract

Transition-metal dichalcogenides exhibit strong quantum confinement effects, and their electronic structure is strongly dependent on the number of layers. Resolving the thickness-dependent electronic structure is important. While the electronic structure of atomically thin 2H-MoSe₂ or 2H-MoS₂ have been explored, information on the experimental electronic structure of 2H-MoTe₂ is still missing. Here, by using nanospot angle-resolved photoemission spectroscopy (nanoARPES), we reveal the experimental electronic structure of exfoliated 2H-MoTe₂ thin flakes with different thickness (three, five, and seven monolayers). Well-separated quantum-well states are clearly observed in thin 2H-MoTe₂ flakes at deep valence bands at energies between -3 to -5 eV, while those at the top of the valence band between -1 and -2 eV are much more closely spaced compared with those from 2H-MoSe₂ and 2H-MoS₂. First-principles calculation shows that the main difference is attributed to the weaker hybridization and smaller energy difference between Mo 4d _z² and Te 5p _z orbitals as compared with Se 4p _z and S 3p _z orbitals. Our work demonstrates the power of nanoARPES in resolving the electronic structure of atomically thin exfoliated flakes.