Optimizing Au-Assisted Exfoliation of Layered Materials with (3-Aminopropyl)triethoxysilane (APTES) for Large-Area Monolayers

Two-dimensional (2D) materials have gained significant scientific interest owing to their exceptional properties and potential applications. Recently, Metal-assisted exfoliation technique has emerged as a valuable method for obtaining large and high-quality 2D monolayers. However, the process efficiency can be hampered by poor adhesion between the metal foil and the substrate. In this study, we address this issue by investigating surface functionalization of the target substrate using (3-Aminopropyl)triethoxysilane (APTES). The introduction of APTES significantly enhances adhesion between monolayers and hydrophilic substrates, overcoming delamination issues associated with the Au-exfoliation method. We perform a comprehensive comparison between APTES-functionalized Au-exfoliated flakes and those obtained through conventional scotch tape exfoliation, evaluating process yield and monolayer quality. Characterization techniques, including ellipsometry, AFM, XPS, Raman spectroscopy, and photoluminescence spectroscopy, confirm the method's effectiveness and superior outcomes in terms of yield and crystal quality. Additionally, we successfully apply this method to obtain high-quality monolayers of other materials, such as BiTeI, which we were able to characterize in terms of SHG, as theoretically predicted. Additionally, we recently refined a Metal-assisted modified exfoliation protocol, allowing for the transfer of the exfoliated flakes onto various flat substrates. This demonstrates the feasibility of achieving extensive exfoliation on rigid substrates (Si, SiO2, ITO, Al2O3) as well as flexible substrates (PET, Kapton).