Recyclable free-polymer transfer of nano-grain MoS₂ film onto arbitrary substrates

Clean transfer of transition metal dichalcogenides (TMDs) film is highly desirable, as intrinsic properties of TMDs may be degraded in a conventional wet transfer process using a polymer-based resist and toxic chemical solvent. Residues from the resists often remain on the transferred TMDs, thereby causing a significant variation in their electrical and optical characteristics. Therefore, an alternative to the conventional wet transfer method is needed—one in which no residue is left behind. Herein, we report that our molybdenum disulfide (MoS₂) films synthesized by plasma-enhanced chemical vapor deposition can be easily transferred onto arbitrary substrates (such as SiO₂/Si, polyimide, fluorine-doped tin oxide, and polyethersulfone) by using water alone, i.e. without residues or chemical solvents. The transferred MoS₂ film retains its original morphology and physical properties, which are investigated by optical microscopy, atomic force microscopy, Raman, x-ray photoelectron spectroscopy, and surface tension analysis. Furthermore, we demonstrate multiple recycling of the resist-free transfer for the nano-grain MoS₂ film. Using the proposed water-assisted and recyclable transfer, MoS₂/p-doped Si wafer photodiode was fabricated, and the opto-electric properties of the photodiode were characterized to demonstrate the feasibility of the proposed method.