Improved one-step zoom and Z-linearity with «Closed-Loop Equivalent» extension.

New Closed-Loop Equivalent (CLE) extension for NT-MDT SPMs allows controlling of actual X-, Y- and Z- position of the probe in the way similar to closed-loop scanners. This extension can significantly improve SPM performance for several important cases:

    One-step zoom and elimination of creep.

Usual open-loop scanners suffer from creep effect and other artifacts caused by nonlinear behavior of the piezotube. These effects usually make difficulties for fast and accurate zooming on small features from the large scan. With CLE extension one can perform one-step zoom with error less than 2% of whole scan range in any location of scan area (see Fig.1). Also it is possible to move scan area without any creep effects.

Fig. 1 Improved one-step zoom with CLE.

Sample – polyethylene microcrystals on mica substrate. This feature is also crucial for nanolithography applications, which require true linear scanning and for metrological measurements.

    Z-linearity.

CLE extension helps to improve Z-linearity of piezoscanners. Scanner nonlinearity in Z direction without correction can achieve 10%, which may cause noticeable artifacts. Usage of CLE decreases this nonlinearity down to 1-2% level.

    Increase of Z-range.

Also new extension enables to increase vertical range of scanning by a factor of ~2.3 without any loss of resolution. With CLE full Z-range of Solver P47H or Solver LS device equipped with standard 90x90x5 um scanner will come to more than 12 um. It is very useful for investigations of such objects as cells and tissues in biology (Fig.2) and for a number of other applications.

Fig. 2 SPM image of tissue section made with increased Z-range. 100x100x10 um scan.

The key feature of CLE is that each NT-MDT SPM can be upgraded with this extension. This unique approach enables any our device to show results that before were achievable only on closed-loop scanning systems.