Investigation of the AFM contact-mode force calibration with simulation

Force-curves measured by Atomic Force Microscopy (AFM) are frequently used to determine the local Young's Modulus of the sample. Originally the AFM (Atomic Force Microscopy) instruments measure the cantilever deflection as a voltage signal; however the natural unit of the deflection is nanometer. In general, the V/nm conversion factor is determined from the force-curve of a hard sample. Since this conversion is highly affects the value of the Young's modulus, the accuracy of this method was investigated experimentally and using a finite element simulation of the cantilever motion. It was found, that the position of the laser spot significantly modify the conversion factor and in case of the sample with steep surface, the error of this calibration method can be significant.