ResearchFields

A Compact XYZ Scanner for Fast Atomic Force Microscopy

This project focuses on the design and characterization of a flexure-based XYZ scanner for fast atomic force microscopy. The scanner consists of a XY nanopositioner, a Z nanopositioner, a base, three piezoelectric stack actuators, two capacitive sensors and a sensor target. The assembly and exploded views of the scanner are shown in Fig. 1. The scanner has resonant peaks at 10kHz for all three axes. It is designed to fit into a NT-MDTNTEGRA scanning probe microscope (SPM) shown in Fig. 2. The XYZ scanner is driven by three external voltage amplifiers PiezoDrive PDL200. This amplifier has a gain of 20 and selectable maximum output voltages of 60V, 150V and 200V.

To evaluate the performance of the scanner, it was installed into a commercial AFM to obtain images. An area of a calibration grating was scanned at 10Hz, 200Hz, 312.5Hz and 625Hz. Oscillations were not observed in the images and time signals. Simulations show that the scanner can be operated at 1025Hz with no scan-induced vibrations observed in the fast axis. However, an image was not recorded at this rate due to the bandwidth limitation of the data acquisition system and the vertical feedback controller. In the future, these two limiting factors will be improved to facilitate high-speed scanning.

Fig. 1
CAD models of the XYZ scanner

Fig. 2
NT-MDT NTERGA scanning probe microscope with the original scanner replaced by the fast flexure-based XYZ scanner.

Fig. 3 - Scan images of the XYZ scanner in 2D and 3D
(a) An area of 3.5um x 3.5um at line rate of 312.5Hz (128 x 128 lines)

(b) An area of 1.5um x 1.5um at line rate of 625Hz (64 x 64 lines)