Atomic Layer Etchings of Transition Metal Dichalcogenides with Post Healing Procedures: Equivalent Selective Etching of 2d Crystal Hetero-Structures

The atomic layer etchings of molybdenum disulfide (MoS2) and tungsten disulfide (WS2) are demonstrated in this paper. By using the oxygen plasma etching and the following re-sulfurization procedures, a mono-layer MoS2 sample with an enhanced photoluminescence intensity is obtained from the sample originally with bi-layer MoS2, which suggests that atomic layer etching of MoS2 can be achieved and the following re-sulfurization procedure can recover the partially oxidized MoS2 remained on the substrate back to a complete MoS2 film. By repeating oxygen plasma etchings and a final re-sulfurization procedure, multi-layer WS2 can be selectively etched off from the WS2/MoS2 hetero-structure. A top-gate WS2/MoS2 hetero-structure transistor is fabricated with source/drain electrodes contacted directly to the MoS2 channel by using the repeated atomic layer etching technique. The results have revealed that the equivalent selective etching effect for 2D crystal heterostructures can be achieved by repeating the atomic layer etching procedure, which is an important step for the device fabrication of 2D crystal hetero-structures.