Accurate Monitoring of Distance Between Two Probes Via Mechanical Interactions
A method to monitor the distance between two tips of tuning fork-based AFM/NSOM systems is described. The distance monitoring is performed by recording the crosstalk signal which characterizes the interaction strength between the two oscillating tuning forks and tips.
|( a) Two Probes Schematic setup. (b) and (c) are images of topographic and Crosstalk (respectively) interactions of the two probes with one scanning probe and a second stationary probe. (d) and (e) are line profiles represent topography and crosstalk signal along the dashed line (d). (e) is integrated signal values along the fast scanning axis.|
The measurements are based on aerodynamic and shear force interactions between the tips. Both interactions increase with decreasing distance between the tips. The shear force interaction is a short-range effect and it is observed within a region of several tens of nanometers. This interaction leads to a sharp increase in the crosstalk signal once the scanning tip comes into the immediate vicinity of the stationary one. This effect is a reliable tool to detect the mechanical interactions between two tips and thus prevent them from colliding during scanning. (Klein et al)
Published: Appl. Phys. B. DOI 10.1007/s00340-012-5182-7 (2012)