Nano Letters, DOI:10.1021/acs.nanolett.5c00928 (2025)
Yating Li, Mengmeng Niu, Junpeng Zeng, Quan Zhou, Xu Wu, Wei Ji, Yeliang Wang, Ren Zhu, Jingsi Qiao, Jianbin Xu, Yi Shi, Xinran Wang, and Daowei He
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 Density Functional
Theory (DFT) calculations. The comparison between experiments and theory allows us to describe ML MoTe2 as a semiconductor with direct gap at 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 display 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 moir´ e heterostructures. Organic semiconductors are highly promising as channel materials for energy-efficient, cost-effective, and flexible electronics. However, grain boundaries (GBs) can cause significant device performance variation, posing a major challenge for the development of high-performance organic circuits. In this work, we effectively passivated GB-induced traps in monolayer organic thin-film transistors (OTFTs) via p-type doping with the organic salt TrTPFB. The doping strategy broadens the mobility edge, effectively shielding GB-induced energy barriers and Coulomb scattering, and promotes deeper nonlocalized hybridization states for conduction. Consequently, the charge transport mechanism transitions from multiple trapping and release (MTR) to a more band-like behavior, even when GBs are present within the device channel. The doped OTFTs demonstrate ultralow mobility variation (1.4%) and threshold voltage variation (4.9%), as well as record-low contact resistant of RC = 0.6 Ω·cm, outperforming most single-crystal technologies. These performance metrics render doped monolayer polycrystalline films highly promising candidates for industrial-scale organic electronics.
DOI: 10.1021/acs.nanolett.5c00928
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