The electronic properties of layered materials are directly determined based on their thicknesses. Remarkable progress has been carried out on synthesis of wafer-scale atomically Molybdenum disulfide (MoS2) as a two dimensional material in the past few years in order to transform them into commercial products. Although chemical/mechanical exfoliation techniques are enable to obtain high quality monolayer of MoS2, the lack of suitable control in the thickness, and lateral size of the flakes restricts their benefits. As a result, a straightforward, effective, and reliable approach is widely demanded to achieve large area MoS2 flake with control in its thickness for opto-electronics applications. In this study, thick MoS2 flakes are obtained by a short time bath sonication in dimethylformamide (DMF) solvent and thinned with the aid of a sequential plasma etching process using H2, O2 and SF6 plasma. A comprehensive study has been carried out on MoS2 flakes based on SEM, AFM, Raman, Tem, and XPS measurements, which ultimately leads to a two-cyclic plasma thinning method. In this approach, H2 does as a passivation step in the first sub-cycle, and O2:SF6 plasma acts as an etching step for removing the MoS2 layers in the second sub-cycle. Finally, we show that this technique can be enthusiastically used to fabricate MoS2 based photodetectors with a considerable photoresponsivity of 1.39 A/W and response-time of 0.45 s under laser excitation of 532 nm.
