2020). Large area, patterned growth of 2D MoS2 and lateral MoS2-WS2 heterostructures for nano-and opto-electronic applications. Nanotechnology, 31(25), [255603]. https://doi. AbstractThe patterned growth of transition metal dichalcogenides (TMDs) and their lateral heterostructures is paramount for the fabrication of application-oriented electronics and optoelectronics devices. However, the large scale patterned growth of TMDs remains challenging. Here, we demonstrate the synthesis of patterned polycrystalline 2D MoS 2 thin films on device ready SiO 2 /Si substrates, eliminating any etching and transfer steps using a combination of plasma enhanced atomic layer deposition (PEALD) and thermal sulfurization. As an inherent advantage of ALD, precise thickness control ranging from a monolayer to fewlayered MoS 2 has been achieved. Furthermore, uniform films with exceptional conformality over 3D structures are obtained. Finally, the approach has been leveraged to obtain in-plane lateral heterostructures of 2D MoS 2 and WS 2 thin films over a large area which opens up an avenue for their direct integration in future nano-and opto-electronic device applications.Supplementary material for this article is available online

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The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/aelm.202100781.

Despite the extensive ongoing research on MoS 2 field effect transistors (FETs), the key role of device processing conditions in the chemistry involved at the metal-to-MoS 2 interface and their influence on the electrical performance are often overlooked. In addition, the majority of reports on MoS 2 contacts are based on exfoliated MoS 2 , whereas synthetic films are even more susceptible to the changes made in device processing conditions. In this paper, working FETs with atomic layer deposition (ALD)-based MoS 2 films and Ti/Au contacts are demonstrated, using current–voltage ( I – V ) characterization. In pursuit of optimizing the contacts, high-vacuum thermal annealing as well as O 2 /Ar plasma cleaning treatments are introduced, and their influence on the electrical performance is studied. The electrical findings are linked to the interface chemistry through X-ray photoelectron spectroscopy (XPS) and scanning transmission electron microscopy (STEM) analyses. XPS evaluation reveals that the concentration of organic residues on the MoS 2 surface, as a result of resist usage during the device processing, is significant. Removal of these contaminations with O 2 /Ar plasma changes the MoS 2 chemical state and enhances the MoS 2 electrical properties. Based on the STEM analysis, the observed progress in the device electrical characteristics could also be associated with the formation of a continuous TiS x layer at the Ti-to-MoS 2 interface. Scaling down the Ti interlayer thickness and replacing it with Cr is found to be beneficial as well, leading to further device performance advancements. Our findings are of value for attaining optimal contacts to synthetic MoS 2 films.

2D metallic TiSx can be grown at low temperatures using atomic layer deposition (ALD). Herein, we show that ultrathin films of 2D TiSx (∼1.2 nm) prepared by ALD can be used as contacts to 2D MoS2 in field-effect transistors (FETs) and improve the overall device metrics.