https://onlinelibrary.wiley.com/doi/10.1002/sstr.202400027

    The 2H-MoTe₂ is a well-known layered two-dimensional semiconductor that is considered as a promising material for next-generation microelectronic and optoelectronic devices. Te deficiency induced defective structures, like Te vacancy and mirror twin boundary (MTB), would be generated at elevated temperatures. However, the temperature dependent evolution of such defects and their influence on the macroscopic electrical transport property of 2H-MoTe₂ is unclear. Here, we report on the semiconductor-metal transition phenomenon in 2H-MoTe_2-x mediated by the evolving disordered mirror twin boundary network with increasing Te deficiency. The samples are grown by molecular beam epitaxy, while the Te deficiency is tuned by post-growth flash annealing in ultra-high vacuum. Low temperature scanning tunneling microscope investigation discloses the medium-range disorder evolution of the MTB network incorporated in the 2H-MoTe₂, which eventually transforms to an ordered metallic Mo₅Te₈ metastable phase. The scanning tunneling spectroscopy shows rich in-gap states localized at the MTBs, which provide a conducting channel in the semiconductor. The UHV in situ I-V measurement shows a gradual decrease of resistance of the sample upon flash annealing from 50 to 480℃, confirming the influence of Te deficiency on the transport property, which would play an essential role in the device performance and durability.

This work was mainly done by Yinuo Zhang and Xueyan Li.