Clean Transfer of MoS₂ by Eutectogels Prepared via In Situ Photopolymerization

Two-dimensional materials and their van der Waals heterostructures have demonstrated enormous potential for advancing technological innovations in electronics, optoelectronics, catalysis, and energy storage. The methods used to synthesize these heterostructures play a crucial role in determining their final applications. In this context, atmospheric pressure chemical vapor deposition (APCVD) has been widely used to synthesize MoS₂ monolayers with tunable optoelectronic properties. However, the growth temperatures of these materials can exceed 700°C, which is incompatible with standard complementary metal oxide semiconductor (CMOS) microfabrication processes. One of the alternatives to this problem is to "transfer" these 2D materials after growth by placing them on substrates that are compatible with these processes without compromising the crystalline quality and uniformity of the 2D material.<br/>Currently, transfer methods are limited and have drawbacks such as introducing defects into the material structure or surface contamination. In addition, the methods are complex and in some cases require the use of sophisticated equipment. To overcome these drawbacks and to minimize residues and structural damage generated during the process, the use of polymers, such as cellulose acetate or PDMS, as support elements for the crystals during their transfer has been reported.<br/>On the other hand, deep eutectic solvents (DES) immobilized into non-aqueous gels, called eutectogels, have emerged as a sustainable alternative to flexible materials with tunable mechanical, thermal and adhesion properties. To achieve the clean transfer of MoS₂ crystals, this study proposes the use of eutectogels obtained from monomer-containing DES (DESm) to asiste in the 2D crystal transfer. By photopolymerizing DESm on MoS₂ crystals in situ, the crystals are transferred to target substrates.<br/>The results obtained by Raman and photoluminescence spectroscopy show that it is possible to transfer MoS₂ crystals without structural damage or impurities introduced during the transfer process.