Thermal measurements using multiple frequency atomic force microscopy
View Patent ↗Apparatus and techniques for extracting information carried in higher eigenmodes or harmonics of an oscillating cantilever or other oscillating sensors in atomic force microscopy and related MEMs work are described. Similar apparatus and techniques for extracting information from piezoelectric, polymer and other materials using contact resonance with multiple excitation signals are also described.
1. A method of operating an atomic force microscope which includes a cantilever probe specialized for thermal measurements through providing two separate legs culminating at a tip and allowing a current to heat the tip, comprising:
heating the tip of the cantilever probe until the onset of local melting;
using a feedback loop to control a distance between a base of said cantilever probe and a surface of a sample to maintain the tip of the cantilever probe in contact with the surface in the Z direction;
exciting a chip of the cantilever probe at two or more different synthesized frequencies that have been summed together by a circuit element;
providing each synthesized frequency as a reference signal to a lock-in amplifier; and
measuring amplitude, frequency and/or phase of the cantilever at the different excitation frequencies.
2. The method according to claim 1 , comprising: displaying the measured amplitude, frequency and phase of the cantilever.