Improving the Accuracy of AFM Measurements: The Thermal Tune Solution (AN90)

The atomic force microscope (AFM) is a sensitive force measurement instrument. But sensitivity and measurement accuracy are two different issues. This application note describes a solution for improving the accuracy of AFM force measurements through more precise calibration of the
AFM cantilever spring constant. There are several well-documented methods for calibrating the spring constant, but the one described here offers not only improved precision, but also ease of use and speed, because the procedure is straightforward, and relies only on the AFM's own hardware and software.

The typical Atomic Force Microscope (AFM) probe is a micro-fabricated cantilever with a sharp tip integrated into its free end (Figure 1). The AFM can directly probe a given location on the sample surface with the tip of this probe, which can sense the surface by either touching it, or by detecting long range forces without coming in direct contact with the surface. Measuring tip-sample forces at a given location on the sample surface is usually called force spectroscopy (see sidebar on next page.)