Tip selection for the resonance frequency / the force constant

For C-AFM utilization, tip parameters are most important to determine the image quality and I-V characteristic correctness.

For example, tip choice about tapping mode at our lab, the cantilevers are made from monocrystalline silicon. Therefore the resonance frequency and the force constant are very precisely determined by the geometry of the cantilever requiring no calibration. The thickness of the cantilever is measured with an interferometric microscope. Length and width are measured with an optical microscope.

Resonance frequency and force constant are calculated with these measured values taking the approximate mass of the tip into account. The measurement errors and the simplifaction used in the calculation lead to the following error values for the resonance frequency and the force constant: In the tip sell market, approximately 10% error for cantilevers 450µm in length, Approximately 20% error for cantilevers 125µm or 225µm in length.

Of course, there are many kinds of tip for vary application areas. One could select suitable tip parameters before try these tips.