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Park Announces New AFM Method for Accurate Sample Topography Without Piezo Creep Error

Published on January 28, 2013 at 4:29 AM

Park Systems announces True Sample Topography™ describing Park technology that eliminates piezoelectric creep errors, resulting in the extremely accurate profile of a sample surface. True Sample Topography™ features an industry-leading Z-detector with a noise level low enough to use it for the AFM topography signal.

In conventional AFM scanning, the application of a calibrated voltage causes the expansion and contraction of a piezoelectric actuator, which moves the scanner accordingly. In this approach, the voltage provides the measuring signal to profile the surface topography. Unfortunately, piezoelectric materials have a tendency to produce creep (continue moving in the same direction) and hysteresis effect (retain properties of a previous state) that introduce positioning errors into the signal. Some AFM systems use closed-loop feedback from additional position detectors to adjust the scanner position and compensate for the errors. However, the feedback applies usually to the X and Y (horizontal) directions and not to the Z direction (vertical, height) because of the typical high level of noise in the Z-direction detector. As a result, when the measuring signal is the applied voltage to the Z-scanner, errors known as edge overshoot and trailing edges often occur.

With True Sample TopographyTM Park AFM overcomes the Z-scanner errors with its industry-leading low-noise (0.2 angstrom) Z-position detector. This detector is so accurate that it provides the topography signal for the closed-loop system. It enables extremely accurate height (topography) recording of sample surface features even during high-speed scanning.

Dr. Sang-il Park, the founder and CEO of Park System notes, “Piezo creep is caused by the intrinsic materials property of a piezoelectric actuator that drives the Z scanner. The only way to correct this artifact is to use an independent position sensor that directly measures the topography. In True Sample TopographyTM, piezo creep error is corrected by independent position sensors, and their noise level is low enough to be a topography signal.”

The Z detector is the key technical advance of the new Park NX product line, which includes the Park NX10, a premium research-grade small sample AFM, and the Park NX20, a high-end large-sample AFM designed for failure analysis and quality assurance applications. The NX technology builds on Park’s leadership in AFM data accuracy with features such as True Non-Contact ModeTM and Crosstalk EliminationTM that add up to the most accurate and reliable atomic force microscopes on the market. For more details and information, please visit us at www.parkAFM.com.

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