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Description:
Combined scanning tunnelling and atomic force microscopy using a qPlus sensor enables the measurement of electronic and mechanic properties of two dimensional (2D) materials at the nanoscale. In this work we study hexagonal boron nitride ( h -BN) , an atomically thin 2D layer, that is van der Waals coupled to a Cu(111) surface. The system is of interest as a decoupling layer for functional 2D heterostructures due to the preservation of the h -BN bandgap and as a template for atomic and molecular adsorbates owing to its local electronic trapping potential due to in-plane electric field. We obtain work-function (Φ) variations on the h -BN/Cu(111) superstructure in the order of 100 meV using two independent methods, namely the shift of field emission resonances (FER) and contact potential difference (CPD) measured by Kelvin probe force microscopy (KPFM). Using 3D force profiles of the same area we determine the relative stiffness of the Moir\'e region allowing us to analyze both electronic and mechanical properties of the 2D layer simultaneously. We obtain a sheet stiffness of 9.4 ± 0.9 nm which is an order of magnitude higher than the one obtained for h -BN/Rh(111).Using constant force maps we are able to derive height profiles of the h -BN/Cu(111) showing that the system has a corrugation of 0.6 ± 0.2 Å which helps demystify discussion around the flatness of the h -BN/Cu(111) substrate.