Friction force microscopy (FFM) with ultrasharp probing tips in liquid environments is a promising technique for relating mechanical and crystallographic properties of mineral surfaces at the nanoscale. Here we will present lattice resolved FFM images of calcite, dolomite, and kyanite cleavage surfaces in water [1, 2] and show how the stick-slip mechanism detected in this way can be interpreted within a well-established model for atomic scale friction. Interestingly, the same technique is capable of identifying the orientation of large organic molecules in ultrathin films self-assembled on dolomite (Fig. 1) [3] and even on the exposed surfaces of bulk organic crystals. The improved resolution achieved in water, as compared to similar measurements in ambient conditions, is consistent with the results of original molecular dynamics simulations of the stick-slip process in water, which have been performed by the group of Prof. Ruben Perez [4]. In the second part of the talk we will discuss the application of FFM to the controlled detachment of mineral islands formed by heteroepitaxial growth. This will be done on the examples of calcite/dolomite and calcite/kutnahorite systems [5]. Not so surprisingly, the shear stress required to detach the adsorbates turns out to be larger when the lattice mismatch is lower. This quantity can be measured by FFM in a straightforward way, by dividing the friction peak observed when an island is being detached by the area of the same island, as estimated from previous FFM images. [1] C.M. Pina et al., Phys. Rev. B 85 (2012) 073402 [2] C. Pimentel et al., Surf. Sci. 635 (2015) 123 [3] P. Nita et al., Nanoscale 6 (2014) 8334 [4] G. Vilhena et al., under review [5] C. Pimentel et al., Cryst. Growth Des. 13 (2013) 2557

Friction force microscopy in water: A powerful technique for mechanical-crystallographic investigations

251st National Meeting (2016)

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