Unveiling Boundary-Localized Interfacial Interactions in Temperature-Controlled Au-Assisted Exfoliation of MoS2 Monolayers

Gold-assisted exfoliation is an effective approach to obtain clean and large-area monolayers of transition metal dichalcogenides, yet the microscopic evolution of interfacial adhesion remains poorly understood. Here, we investigate temperature-controlled exfoliation of MoS₂ between 30 and 170 °C. Based on optical microscopy image analysis, mild heating slightly improves the exfoliation yield, which is associated with the release of interfacial contaminants and trapped gases-these substances enhance the adhesion between gold and molybdenum disulfide (Au-MoS₂). Unexpectedly, as revealed by AFM, SEM-EDS, and Raman analyses, parts of the Au film start to peel off from the underlying Ti adhesion layer at approximately 100 °C. This Au film detachment, resulting from the surprisingly weak Au-Ti adhesion, serves as a unique probe for interfacial strength: it preferentially occurs at the boundaries of MoS₂ flakes, indicating that the reinforcement of the Au-MoS₂ interaction originates at the edges rather than being uniformly distributed. At higher temperatures (>130 °C), Au detachment expands to larger areas, indicating that boundary-localized adhesion progressively extends across the entire interface. Additional STM/STS measurements further confirm that thermal annealing improves local Au-MoS₂ contact by removing interfacial species and enabling surface reconstruction. These findings establish a microscopic picture of temperature-assisted exfoliation, highlighting the dual roles of interfacial contaminant release and boundary effects, and offering guidance for more reproducible fabrication of high-quality 2D monolayers.