System positioning error compensated by local scan in atomic force microscope based nanomanipulation

Atomic force microscopy (AFM) has been used as a nanomanipulation tool for a decade taking advantage of its high precision and resolution. But due to thermal drift, nonlinear and hysteresis of piezo scanner, a lot of spatial uncertainties associates with the motion of AFM tip, which makes it difficult to move the tip to a desired position accurately. A lot of work has been carried out to improve the positioning accuracy of AFM tip. But most of them only compensate the positioning error in horizontal space, seldom paper pays attention to the vertical positioning error caused by the system structure. To enhance the positioning precision in 3-D space, this paper mainly addresses what causes the position error in vertical direction and how to on-line compensates it. It reveals that when the tip is mounted with an offset to the tube axis, the bow-effect of the piezo scanners will increase the position error seriously. In addition, a local scan based method is proposed to compensate this error. The experimental results are presented to demonstrate the effectiveness of the proposed method