Large-area high-speed scanning probe microscopy using legacy scanners.

Abstract

In scanning probe microscopy, the scanner dynamically positions the sample relative to the probe, and the upper limit of the imaging speed is governed primarily by the first eigenfrequency of the scanner. The mechanical oscillations of the scanner-even when it operates far from resonance-give rise to image artifacts and negatively affect the image resolution. This paper analytically and experimentally investigates the scanner's dynamics at high scan rates upon scanning over a large area. At slow scan speeds, the frequency spectra of the microcantilever's deflection signal exhibit only the excitation frequency and its harmonics; in contrast, at high scan speeds, the spectra exhibit sidebands centered around the excitation harmonics and separated from them by the scanner's eigenfrequency. Exploiting this phenomenon, a scanner dynamics-based method is proposed to reconstruct the surface topography, and, thereby, to reduce the oscillation-induced image artifacts. The method is proven for a variety of sample surfaces at very high scan rates up to 59.2 Hz (corresponding to a linear speed of 4.74 mm/s) upon scanning over a 40 μm × 40 μm area and is successfully demonstrated to be able to virtually eliminate any image artifacts. A nearly ten-fold increase in the scan rate is demonstrated using even a legacy scanner, with no changes required to the hardware.