Experimental and Computational Assessment of Adsorbates in Ultraclean 2D MoS

Two-dimensional semiconductor-transition-metal dichalcogenide (2D-STMD) based semiconductors have emerged as promising materials for future spintronic and optoelectronic applications, including photodetectors and transistors. Transferring high-quality chemical vapor deposition (CVD)-grown monolayer 2D-STMDs and their alloys to the target substrate is very challenging for fabricating efficient devices. Unfortunately, current post-transfer methods struggle to completely remove unwanted contamination residues during wet-transfer processes, which adversely affects material quality and intrinsic properties. In this work, the effect of ethanol cleaning on the qualitative and quantitative assessment of molecular adsorbates is demonstrated, based on atomic-resolution high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) image analysis supported by X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), and density functional theory (DFT) calculations, which showcases ultraclean material structures. We estimate the unidentified molecular adsorbates in the proximity of molybdenum (Mo) and chalcogen (S, Se) atomic sites, which are tentatively assigned as 'C