Methods of operating atomic force microscopes to measure friction

• Main Author: ELINGS; VIRGIL B
• Format: Patent
• Language: English
• Published: 28.03.1995
• Edition: 6
• Subjects: APPLICATIONS OF SCANNING-PROBE TECHNIQUES, e.g. SCANNING PROBEMICROSCOPY [SPM]; MEASURING; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS; MEASURING LENGTH, THICKNESS OR SIMILAR LINEARDIMENSIONS; PHYSICS; SCANNING-PROBE TECHNIQUES OR APPARATUS; TESTING

A method of operating an atomic force microscope having a probe tip attached to a free end of a lever which is fixed at its other, wherein the probe tip is scanned in forward and reverse directions in a common scanline across the surface of a sample and either the deflection of the lever or the height of the sample is detected during the forward and reverse scans. The difference between the deflection of the lever or the sample height in the forward and reverse scans is determined as a relative measure of friction. A signal relating to the normal force applied to the sample, can be determined and based thereon, a coefficient of friction of the simple is determined. The signal relating to normal force is derived either from a force curve, or by scanning the probe at different force setpoints. To enhance accuracy of topographical data, the scanning angle is varied in order to minimize differences between the probe deflection (or sample height) during scanning in the forward and reverse directions. Once it is determined which angle results in minimum difference in data obtained during scanning in the forward and reverse directions in a common scanline, topographical data is obtained by scanning the sample at that angle. Frictional data is obtained by scanning at that angle which maximizes the difference between data obtained in forward and reverse scanning directions in a common scanline.