Accurate AFM Solutions

Non-Linear XY Scan

The conventional AFM uses a piezoelectric tube for the x-y-z scanner, where x-y motion relies on the bending of the tube. The bending motion, however, introduces background curvature and causes a high-order and non-linear scan, which is the primary cause for inaccurate and processed images. Software flattening is usually needed for conventional systems to hide the background curvature. A "flat surface" obtained through software flattening, however, cannot produce a truly flat image since the amount of curvature depends on various parameters including scan size, scan speed, x-y offset, z position, etc. Through software flattening, the scan also fails to display orthogonality, and produces significant X and Y shifting.

High background curvature
Software processing required (processed data)
Results highly dependent on scan location

Park AFM Solution: Flat Orthogonal XY Scanning Without Scanner Bow

Park's Crosstalk Elimination removes scanner bow, allowing flat orthogonal XY scanning regardless of scan location, scan rate, and scan size. It shows no background curvature even on scans of the flattest samples such as that of an optical flat, even with various scan offsets. This enables very accurate height measurement and precision nanometrology for the most challenging problems in research and industry.

Difficulty in Tip and Sample Preservation

Conventional AFM uses a tube scanner with a slow actuator that has highly limited Z-scan bandwidth of only 500 Hz or so. The Z-servo response is too slow to implement Non-Contact Mode, a critical requirement for preservation of tip sharpness and non-destructive imaging of soft biological samples.

Quick tip wear = Blurred low-resolution scan
Destructive tip-sample interaction = Sample damage and modification
Highly parameter-dependent

Park AFM Solution: Non-destructive Scanning by Non-Contact AFM

Park's development of Crosstalk Elimination and high force Z-scanner with large Z-servo bandwidth enables True Non-Contact Mode^TM. It minimizes tip and sample damage and prolongs high-resolution imaging, ultimately producing the most
accurate and reproducible AFM results.

Position Error by Piezo Creep

Conventional AFM calibrates the applied voltage to the Z scanner and uses it for the Topography signal. However, the hysteresis of piezoelectric actuators in the Z scanner causes positional errors, especially when the cantilever moves in the direction perpendicular to the surface, resulting in edge overshoots at the leading and trailing edges. Hence, the piezo creep affects the accuracy of the height measurement. Moreover, the initial calibration will change over time as the piezoelectric material ages and requires laborious recalibration.

Applied voltage to Z scanner is used for Topography
Hysteresis of piezoelectric actuators causes errors
Edge overshoot at the leading and trailing edges
Requires regular calibrations as the piezoelectric actuator ages

Park AFM Solution: Sample Topography Measured by Low Noise Closed-Loop Sensors

Piezo creep error can only be corrected by independent position sensors, whose noise level is low enough to be used as the topography signal. The Park's advanced XYZ closed-loop scanning is based on industry-leading low-noise Z position sensor. By using a Z position sensor to monitor the real-time extension of the Z scanner, the true heights of sample surface features are recorded, even during high-speed scanning, without the effects of piezo creep or edge overshoot. With its advanced closed-loop scanning design, True Sample Topography^TM is obtained without any need for frequent and cumbersome recalibration.