chematic drawing of the FM-AFM setup. A very small tip is mounted on an
oscillating cantilever 1 that is in vicinity of a sample. The oscillation of the cantilever
changes upon interaction between the tip and the sample and is detected with a laser beam
2 focussed on the back of the cantilever. The reflected beam travels via mirrors to a position
sensitive detector (PSD) 3 . The signal of the PSD is amplified by a preamplifier. An
amplitude control 4 measures the amplitude A of this signal and a feedback loop compares
it with a setpoint and determines the amplification (dissipation Γ) of the excitation signal
6 for the cantilever which is fed to a shaking piezo. To measure the current resonance
frequency, a phase-locked loop (PLL) 5 is used. Its voltage-controlled oscillator (VCO)
produces the excitation signal 6 for the cantilever. The detected frequency shift ∆f is
passed to another feedback loop 7 that keeps the frequency shift constant by changing the
distance between the tip and the surface (z position) by varying the voltage applied to the

piezo tube.
Own work
DeepKling