A review of scanning methods and control implications for scanning probe microscopy

In a scanning probe microscope (SPM), the image is obtained by scanning a sample relative to a physical probe which captures the topography. The conventional scanning method is a raster pattern where a triangular or sawtooth waveform is applied to the x-axis while the y-axis position is incremented. In recent years the need for higher imaging speeds has motivated the investigation of novel scanning trajectories such as spiral, cycloid, and Lissajous patterns. Although the benefits of these approaches has been described in the literature, the lack of a comprehensive comparison makes the actual performance gains, if any, unclear. This article evaluates the efficacy of current scanning methods by comparing the required scan rate, signal bandwidth, sampling frequency, and probe velocity. In addition, the control implications of each method are also discussed qualitatively. Based on the prescribed performance metrics, the sinusoidal raster method significantly outperforms the raster, spiral, and Lissajous methods whilst being the simplest to implement. Therefore, it is concluded that the most suitable currently known method for high-speed or video-rate AFM imaging is sinusoidal raster scanning.