A PRESCAN METHOD IMPROVING THE REPRODUCIBILITY OF FORCE-DISTANCE CURVES OBTAINED WITH A PIEZOELECTRIC TUBE SCANNER

We present a method based on pre- and postscanning a piezoelectric tub e scanner used in a force probe that improves the reproducibility of t he scan lengths. Instead of prescanning in the same direction as when acquiring data (the z direction), which could destroy a sensitive surf ace, we perform lateral (x/y direction) prescans. As lateral motions o f the tube scanner involve out of phase elongations and compressions o f the tube in the z direction, these kinds of prescans will have a sta bilizing effect on the z motion as well. By adding an additional posts can in the +/-z directions, we reduce the piezoelectric creep followin g the data acquisition scan. When comparing the lengths of z scans wit h and without the pre/postscan procedure, preceded by a z voltage step 60 s before data acquisition, the deviation between four consecutive scans improved from 12% to 1.4%. (C) 1996 American Institute of Physic s.