Use of a fibre-based light sensor for the calibration of scanning probe microscopy piezos

Scanners for Scanning Probe Microscopes (SPM) are generally built of piezos, which are used to move the sample with respect to the tip in x-, y- or z-direction or vice versa. These piezoelectric scanners are usually calibrated by the manufacturer with laser interferometry, with a calibration grid or with the crystallographic or artificial step of a known height standard. However, the displacement depends on the voltage history of the piezoelectric device. In order to avoid this effect for the x- and y-positions, SPM data are generally collected in one lateral direction to minimize the divergence between commanded position and true position. The aim of this work is to present the usefulness of a cheap and easy-to-use fibre optic displacement sensor. The sensor can be used to measure static and dynamic displacement of a z-piezo in order to find a calibration procedure or at least an error look-up table for open-loop systems. The collected data of two different piezo scanner types can be used to characterize their nonlinearity and hysteresis.