Figure 10.

Atom tracking measurement with the FastSPM system in a UHV-STM: (left) Treble clef pattern generated by the matrix SPM controller via a MATE script, applied as tip offset. The pattern is defined as linear segments of different speeds (50 and 100 nm/s, color coded); start point and direction are indicated by an arrow. (center and right) Resulting tracking measurements (lateral PI feedback outputs) with an STM tip locked on a magnetite-supported Pt₅ cluster at a rotation frequency of 4.74 kHz and measured with a 500 µs time resolution. The two measurements differ in the PI parameter settings, demonstrating the importance of proper parameter tuning for features that propagate at high speeds. Two red circles indicate cluster shape changes that shift the detected cluster position of the trace back and forth by the same amount. The trace between these discontinuities therefore appears to be shifted to higher y-values. With appropriate PI parameters, reliable tracking can be achieved down to a fraction of an Å.