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Design, Characterization, and Control of a High-Bandwidth Serial-Kinematic Nanopositioning Stage for Scanning Probe Microscopy Applications
AuthorKenton, Brian J.
AdvisorLeang, Kam K
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This thesis focuses on the development of a new three-axis serial-kinematic nanopositioning stage for high-bandwidth applications. Particularly, the nanopositioner is designed to be integrated with commercial scanning probe microscopes (SPMs), such as scan-by-probe atomic force microscopes (AFMs), for video-rate imaging and highthroughput probe-based nanomanufacturing. The positioning stage employs uniquely designed compliant flexures for guiding the motion of the sample platform to minimize parasitic motion (runout) and off-axis effects compared to previous designs. Finite element analysis (FEA) predicts the dominant resonances along the fast (x-axis) and slow (y-axis) scanning axes at 25.9 and 5.96 kHz, respectively. The first mechanical resonance modes for each stage are axial (i.e. piston). A monolithic prototype is fabricated from aluminum alloy using the wire electric discharge machining process. The performance of the positioning stage is evaluated and the measured dominant lateral resonances in the fast and slow scanning directions are 24.2 and 6.00 kHz, respectively, which are in good agreement with the FEA predictions. In the vertical (z) direction, the measured dominant resonance is approximately 70 kHz. The lateral and vertical positioning range is measured at approximately 9×9 μm and 1 μm, respectively. Four approaches to control the lateral motion of the stage are evaluated for precision tracking at high-scan rates: (1) open-loop smooth inputs, (2) PID feedback, (3) discrete-time repetitive control implemented using FPGA hardware, and (4) model-based feedforward control. Atomic force microscope imaging and tracking results are presented to demonstrate the performance of the stage. It is shown that the stage can be utilized for video-rate AFM imaging with line rates in excess of 7,000 Hz. Compared to the positioning stage found on a basic commercial AFM system (e.g. NanoSurf EasyScan AFM), the newly developed nanopositioner offers an improvement in the line rate by a factor of 700 (10 Hz to 7,000 Hz).