Synthesis and electronic structure of atomically thin 2H-MoTe2†

Abstract

An in-depth understanding of the electronic structure of 2H-MoTe₂ at the atomic layer limit is a crucial step towards its exploitation in nanoscale devices. Here, we show that millimeter-sized monolayer (ML) MoTe₂ samples, as well as smaller sized bilayer (BL) samples, can be obtained using the mechanical exfoliation technique. The electronic structure of these materials is investigated by angle-resolved photoemission spectroscopy (ARPES) for the first time and by density functional theory (DFT) calculations. The comparison between experiments and theory allows us to describe ML MoTe₂ as a semiconductor with a direct gap at the K point. This scenario is reinforced by the experimental observation of the conduction band minimum at K in Rb-doped ML MoTe₂, resulting in a gap of at least 0.924 eV. In the BL MoTe₂ system, the maxima of the bands at Γ and K show very similar energies, thus leaving the door open to a direct gap scenario, in analogy to WSe₂. The monotonic increase in the separation between spin-split bands at K while moving from ML to BL and bulk-like MoTe₂ is attributed to interlayer coupling. Our findings can be considered as a reference to understand quantum anomalous and fractional quantum anomalous Hall effects recently discovered in ML and BL MoTe₂ based moiré heterostructures.