Atomic force microscopy calibration methods for lateral force, elasticity, and viscosity

Due to huge uncertainties in the geometric dimensions of atomic force microscopy (AFM) probes, samples' rheological properties and lateral forces are difficult to measure and compare quantitatively. Hence, mathematical calibration methods fail to calibrate AFM probes accurately. To solve this problem, we will introduce in this paper `blind calibration methods' to determine quantitatively lateral forces, elastic constants and viscosity. For lateral force, a geometry factor is used to calibrate any cantilever using this `blind method'. The essential part of this method is a calibration standard sample that is commercially available. We have chosen silicon for our calibration standard sample and will discuss a cleaning procedure for reproducible lateral force measurements. We will provide an absolute friction value, which will serve as one of three parameters necessary to obtain the geometry factor. The other two components being the normal spring constant and the relative friction signal measured with the cantilever of interest. Further, we will discuss force modulation measurements and the problems that occur around resonances. We will provide a procedure to determine elastic constants also based on the silicon calibration standard. Finally, the `blind calibration method' will also be used to achieve kinematic viscosity values.