The strength of van der Waals interactions in layered materials is commonly described through the Hamaker constant, although experimental values often exhibit substantial dispersion due to environmental contamination, capillary forces, probe geometry, and differences in data analysis. In this work, adhesion measurements were performed on few-layer graphene, MoS₂, and SiO₂ using calibrated atomic force microscopy probes under ultrahigh-vacuum conditions and after in situ thermal cleaning. Measurements obtained by static force spectroscopy were compared with noncontact frequency-modulation AFM, providing a complementary assessment of the interaction strength. The resulting mixed Hamaker constants were consistent with dielectric-response and Lifshitz-based theoretical estimates. Controlled humidity cycles showed that adsorbed water and capillary condensation produce a strong and reversible increase in adhesion, even at relatively low humidity. These results define experimental reference conditions for the quantitative characterization of van der Waals interactions in two-dimensional materials. [Full Article]
