The atomic layer etching of molybdenum disulfides using low-power oxygen plasma

The layered removal mechanisms of molybdenum disulfides (MoS2) using low-power oxygen plasma are investigated in this paper. After the low-power oxygen plasma treatment, the topmost MoS2 layer is completely oxidized. The weaker adhesion of Mo oxides with MoS2 surfaces would lead to the detachment of the topmost oxidized MoS2 layer from the underlying MoS2 films. Since MoS2 is insoluble and Mo oxides are soluble in water, an additional dipping procedure of the sample in de-ionized water will help with the complete detachment of the topmost oxidized MoS2 layer. With a re-sulfurization procedure after the removal process, the partially oxidized MoS2 film remaining on the substrate can be recovered back to a complete MoS2 film. Both optical and electrical characteristics of the MoS2 films can be maintained after the removal procedure. By repeating the same procedure, a layer-by-layer removal of MoS2 is demonstrated, which provides an easy and fast approach to determine the number of layers of the 2D material.