Atomic force microscope with improved scan accuracy, scan speed, and optical vision

Abstract

We have developed a new atomic force microscope (AFM), with a z scanner independent of the xy scanner. Unlike conventional AFM systems, our xy scanner moves only the sample in the xy plane, while the z scanner controls the AFM probe along the z axis. The xy scanner is a single module parallel-kinematics flexure stage that guarantees high orthogonality and minimum out-of-plane motion. The z scanner is a one-dimensional flexure stage with negligible out-of-axis motion. Separating the z scanner from the xy scanner practically eliminates the x–z cross coupling problem inherent in conventional AFMs. Furthermore, the z servo response is no longer limited by the xy scanner characteristics, allowing us to make full use of our high performance z scanner. Our system uses the laser beam bounce detection method, and only the cantilever and the photodetector are mounted on the z scanner to realize a lightweight probing unit. We have devised a unique design such that the photodetector signal measures only the cantilever deflection and not the z-scanner motion. Our new AFM provides fast z servo response and high scan accuracy.