A Novel Methodology of Using Nonsolvent in Achieving Ultraclean Transferred Monolayer MoS2

Abstract The transfer of monolayer molybdenum disulfide (1L‐MoS 2 ) onto any target substrates is inevitable for the next generation of optoelectronic devices such as flexible electronics. However, the existing post‐transfer treatments are ineffective for the complete removal of poly(methyl methacrylate) (PMMA) polymer, which is usually used as carrier polymer in the wet‐transfer method. The presence of PMMA residues seriously degrades the intrinsic properties of any 2D materials. Several new cleaning methods such as annealing, ozone cleaning, and acetone treatment adopted in this report are found to be ineffective for the complete removal of PMMA residues on the transferred 1L‐MoS 2 film. A new chemical route is developed and demonstrated with a PMMA nonsolvent, ethanol, and ultraclean transferred 1L‐MoS 2 is obtained after 96 h hot ethanol treatment. An interfacial diffusion model is proposed for the mechanism of PMMA removal from the 1L‐MoS 2 surface. To observe the effect of cleaning process on electrical properties, 1L‐MoS 2 field‐effect transistor (FET) devices are fabricated. An enhancement of 80%–85% in the electron mobility is achieved for ultraclean 1L‐MoS 2 . One order improvement in the FET parameters such as ON/OFF ratio and the subthreshold slope is also observed. It is believed that this novel method can also be applicable for other 2D materials.