Methods for vertical drift measurements of scanning probe microscopes.

Time stability plays an important role in the applications of scanning probe microscopes (SPMs). Although SPMs integrated with a closed-loop control system could reduce the drift greatly, drift would still exist. The SPM drift in the lateral direction has been well studied, and several measurement methods have also been developed. However, due to coupling of the lateral drift, it is still difficult to determine the drift in the vertical direction. In this paper, we propose a method to measure the vertical drift of an SPM based on scanned topography images. This method considers the influence of the lateral drift. Experimental results show that the vertical drift of the SPM is non-negligible, and the vertical drift on each pixel of one scanned image is different from each other. By such a method, instability in the vertical direction of the SPM instrument could be revealed and evaluated.