lines at a relative distance of d = 160 nm. In order to make the surface conductive, AuPd is evaporation-deposited on top. From these measurements scaling factors of 30 . 0 nm/V for ± x movement and 43 . 1 nm/V for ± y movement are obtained. HOPG is used for the calibration of the piezo positioning elements, as is often done as a standard procedure for two reasons: First, it is relatively easy to get atomic resolution on HOPG, and second, the preparation of a clean surface is very simple. As HOPG has a layered structure, a fresh surface can be obtained by using adhesive tape to remove some of the top layers. The lattice parameters are well known from literature: the nearest neigh- bor distance is 0 . 142 nm, whereas the in-plane lattice constant is 0 . 246 nm [10]. To achieve 10 FIG. 6: Raw data of the atomic resolution on HOPG ( V$_{bias}$ = 76 mV, I = 2 nA) at room tem- perature and ambient pressure. The lower graph shows the line profile marked in the scan. The well-known lattice constant was used to calibrate the scan head for room temperature and small scanning areas.