Spectro-Microscopic Perceptions into Oxidation Behavior of Large-Scale Molybdenum Disulfide and its Photoelectrical Correlation.

Despite the encouraging properties and research of 2D MoS 2 , an ongoing issue associated with the oxidative instability remains elusive for practical optoelectronic applications. Thus, in-depth understanding of the oxidation behavior of large-scale and homogeneous 2D MoS 2 is imperative. Here the structural and chemical transformations of large-area MoS 2 multilayers by air-annealing with altered temperature and time via combinatorial spectro-microscopic analyses (Raman spectroscopy, X-ray photoelectron spectroscopy, and atomic force microscopy) are surveyed. The results gave indications pertaining to temperature- and time-dependent oxidation effects: i) heat-driven elimination of redundant residues, ii) internal strain stimulated by the formation of MoO bonds, iii) deterioration of the MoS 2 crystallinity, iv) layer thinning, and v) morphological transformation from 2D MoS 2 layers to particles. Photoelectrical characterization of the air-annealed MoS 2 is implemented to capture the link between the oxidation behavior of MoS 2 multilayers and their photoelectrical properties. The photocurrent based on MoS 2 air-annealed at 200 °C is assessed to be 4.92 µA, which is 1.73 times higher than that of pristine MoS 2 (2.84 µA). The diminution in the photocurrent of the photodetector based on MoS 2 air-annealed above 300 °C in terms of the structural, chemical, and electrical conversions induced by the oxidation process is further discussed.