High-speed Lissajous-scan atomic force microscopy: Scan pattern planning and control design issues
Review of Scientific Instruments
An atomic force microscopy-based method for line edge roughness measurement J. Appl. Phys. 113, 104903 (2013) Atomic force microscope infrared spectroscopy on 15 nm scale polymer nanostructures Rev. Sci. Instrum. 84, 023709 (2013) Bias controlled capacitive driven cantilever oscillation for high resolution dynamic force microscopy Appl. Phys. Lett. 102, 073110 (2013) Friction measurement on free standing plates using atomic force microscopy Rev. Sci. Instrum. 84, 013702 (2013) A correlation
... ) A correlation force spectrometer for single molecule measurements under tensile load J. Appl. Phys. 113, 013503 (2013) Additional information on Rev. Sci. Instrum. Tracking of triangular or sawtooth waveforms is a major difficulty for achieving high-speed operation in many scanning applications such as scanning probe microscopy. Such non-smooth waveforms contain high order harmonics of the scan frequency that can excite mechanical resonant modes of the positioning system, limiting the scan range and bandwidth. Hence, fast raster scanning often leads to image distortion. This paper proposes analysis and design methodologies for a nonlinear and smooth closed curve, known as Lissajous pattern, which allows much faster operations compared to the ordinary scan patterns. A simple closed-form measure is formulated for the image resolution of the Lissajous pattern. This enables us to systematically determine the scan parameters. Using internal model controllers (IMC), this non-raster scan method is implemented on a commercial atomic force microscope driven by a low resonance frequency positioning stage. To reduce the tracking errors due to actuator nonlinearities, higher order harmonic oscillators are included in the IMC controllers. This results in significant improvement compared to the traditional IMC method. It is shown that the proposed IMC controller achieves much better tracking performances compared to integral controllers when the noise rejection performances is a concern.