Drift Compensation in AFM-Based Nanomanipulation by Strategic Local Scan

The drift distorts the atomic force microscopy (AFM) images as the time taken to acquire a complete AFM image is relatively long (a few minutes). As the AFM image is used as a reference for most manipulation mechanisms, the image distorted by drift will cause problems for AFM-based manipulation because the displayed positions of the objects under nanomanipulation do not match their actual locations. The drift during manipulation, similarly, will further exacerbate the mismatch between the displayed positions and the actual locations. Such mismatch is a major hurdle to achieve automation in AFM-based nanomanipulation. Without proper compensation, manipulation based on a wrong displayed location of the object often fails. In this paper, we present an algorithm to identify and eliminate the drift-induced distortion in the AFM image by applying a strategic local scan method. Briefly, after an AFM image is captured, the entire image is divided into several parts along vertical direction. A quick local scan is performed in each part of the image to measure the drift value in that very part. In this manner, the drift value is calculated in a small local area instead of the global image. Thus, the drift can be more precisely estimated and the actual position of the objects can be more accurately identified. In this paper, we also present the strategy to constantly compensate the drift during manipulation. By applying local scan on a single fixed feature in the AFM image frequently, the most current positions of all objects can be displayed in the augmented reality for real-time visual feedback.