Calibration of surface stress measurements with atomic force microscopy

An accurate method to calibrate a commercial atomic force microscope (AFM) with commercial cantilevers for surface stress measurements was investigated. The bending of commercial rectangular cantilevers of the AFM was measured by laser beam deflection under a concentrated load mode and a bending moment mode. Good agreement between the experimental results and the theoretical predictions was obtained. The accurate calibration of the deflection angle for Δσ was possible with the rectangular cantilever by taking into account the dependence of the deflection angle on the laser spot position, $\mathrm{a,}$ on the cantilever. The cyclic voltammogram and the electrocapillary curve were measured in the double layer region of a gold thin film on the rectangular cantilever. In addition, it was concluded that a fairly good measurement of Δσ by triangular cantilevers was also possible as long as the deflection angle measurement was carried out with the same triangular cantilever at the same laser spot position $\mathrm{a.}$ The change in surface stress due to electrochemical oxygen and hydrogen adsorption was also studied on gold and platinum deposited on rectangular cantilevers. In these cases, the change in reflectance of the cantilevers by electrochemical reactions had to be taken into account for accurate calibration. The discussion described here will be also useful for other stimuli, such as pH, that cause the cantilever bending.