Direct chemical discrimination at step edges and kink sites of sodium chloride by nc-AFM with an oxygen-terminated copper tip

Since the advent of scanning probe microscopy, elemental- and chemical discrimination on heterogeneous surfaces has been a major challenge. This is mainly due to complex contrast mechanisms, which require considerable indirect structural assumptions of tip and surface and related extensive theoretical modeling. Previously, noncontact atomic force microscopy with atomically defined copper oxide tips (CuOx-tips) showed elemental selectivity on even most complex metal-oxide surfaces [Hütner ., ]. Here we report an investigation of an ionic surface, which allows to directly identify the anionic- and cationic sub lattices even on aperiodic surface structures. In line with previous work on metal oxides [Wiesener ., ], the present results extend chemically selective imaging of CuOx-tips to a new class of heterogeneous materials.