Method Development for Scanning Probe Microscopy

To push the limits of what information can be extracted from experiments, our group strives to continuously improve on existing measurement schemes for high-resolution scanning probe microscopy. Here, we are giving three examples: First, in 2009, we introduced three-dimensional atomic force microscopy (3D-AFM), which allows to quantify the three-dimensional force field over the surface as experienced by the tip with piconewton and picometer resolution. This technique is ideal to characterize interactons at defects and active sites. Subsequently, we demonstrated in 2016 how high-resolution noncontact atomic force microscopy (NC-AFM) imaging can become more robust using tuned-oscillor atomic force microscopy (TO-AFM). Since TO-AFM uses only one feedback loop during imaging, as opposed to the three loops employed in the so-called 'frequency modulation' mode mode of NC-AFM, data acquisition is significantly simplified. As a result, NC-AFM becomes more user friendly, which not only lowers the hurdles for beginners to successfully employing the technique, but also allows to speed up data acquisition in particular for larger surface scans. To make this measurement scheme available to the broader public, it has been patented and licensed to Scienta Omicron, the largest manufacturer of ultrahigh vacuum scanning probe instrumentation, which has commerciallized this mode under the trademark QSpeed. Finally, current efforts are directed towards the controlled manipulation of individual molecules on surfaces, which allows to characterize every step of surface reactions induced along pathways of choice while quantifying energy barriers between individual surface potential minima.