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Abstract Manipulation and structural modifications of 2D materials for nanoelectronic and nanofluidic applications remain obstacles to their industrial‐scale implementation. Here, it is demonstrated that a 30 kV focused ion beam can be utilized to engineer defects and tailor the atomic, optoelectronic, and structural properties of monolayer transition metal dichalcogenides (TMDs). Aberration‐corrected scanning transmission electron microscopy is used to reveal the presence of defects with sizes from the single atom to 50 nm in molybdenum (MoS₂) and tungsten disulfide (WS₂) caused by irradiation doses from 10¹³to 10¹⁶ions cm⁻². Irradiated regions across millimeter‐length scales of multiple devices are sampled and analyzed at the atomic scale in order to obtain a quantitative picture of defect sizes and densities. Precise dose value calculations are also presented, which accurately capture the spatial distribution of defects in irradiated 2D materials. Changes in phononic and optoelectronic material properties are probed via Raman and photoluminescence spectroscopy. The dependence of defect properties on sample parameters such as underlying substrate and TMD material is also investigated. The results shown here lend the way to the fabrication and processing of TMD nanodevices. 

Abstract The large‐scale growth of semiconducting thin films on insulating substrates enables batch fabrication of atomically thin electronic and optoelectronic devices and circuits without film transfer. Here an efficient method to achieve rapid growth of large‐area monolayer MoSe₂films based on spin coating of Mo precursor and assisted by NaCl is reported. Uniform monolayer MoSe₂films up to a few inches in size are obtained within a short growth time of 5 min. The as‐grown monolayer MoSe₂films are of high quality with large grain size (up to 120 µm). Arrays of field‐effect transistors are fabricated from the MoSe₂films through a photolithographic process; the devices exhibit high carrier mobility of ≈27.6 cm²V^–1s^–1and on/off ratios of ≈10⁵. The findings provide insight into the batch production of uniform thin transition metal dichalcogenide films and promote their large‐scale applications.