Converting Z distance (see graphs!)

Definition of raw Z position or scanner height in AFM force curves

The total vertical position or displacement controlled by the piezoelectric actuator as it moves the probe towards or away from the sample

Definition of cantilever deflection d in AFM force spectroscopy

The physical vertical bending of the cantilever, calculated by multiplying the photodiode voltage signal by the deflection sensitivity in nanometers per volt

Definition of tip-sample separation D

The actual physical distance or gap between the apex of the AFM tip and the top surface of the sample

General mathematical relationship between Z position, cantilever deflection d, and tip-sample separation D

Tip-sample separation D equals Z position minus cantilever deflection d, written as D = Z - d

Significance of the contact point z0 and d0 on a force curve

The specific piezo position z0 and deflection d0 where the tip first touches the surface, establishing the zero reference for both tip-sample separation and sample indentation

Behavior of tip-sample separation D on an infinitely hard non-deformable surface after contact

Tip-sample separation D remains zero because every nanometer of downward piezo Z movement produces an equal one nanometer of upward cantilever deflection

Definition and equation for sample indentation depth delta on a soft deformable surface

Indentation depth delta equals the relative piezo movement minus the relative cantilever deflection, expressed as delta = (Z - z0) - (d - d0)

Procedure for converting a raw Force-versus-Z curve into a Force-versus-Indentation curve

First identify the contact point, then subtract baseline deflection and piezo position, convert deflection to force using spring constant, and plot force against calculated indentation delta