At the heart of the instrument, a tip is mounted on a tuning-fork similar to the one found in wrist-watches.
The tuning fork is mounted on a scanner to position the tip in all directions by piezo motors.
The tuning fork acts like a mass connected to a spring and oscillates at its resonance frequency which can be disturbed by a force gradient.
The very small oscillation amplitude allows detecting the frequency shift and the tunneling conductance simultaneously.
The conductance increases exponentially until it saturates into the point contact regime.
Background forces and forces between tip and adsorbate can be discriminated.
The vertical force and the potential can be determined from the cantilever frequency shift.
Simultaneously recorded atomic resolution on CuN in the STM (current) and the AFM (force) channel.
The forces measured on CuN depend on the atom below the tip and its environment.
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