J. Clark
Auburn University,
United States
Keywords: AFM, calibration, atomic force microscope
Summary:
We present a method to calibrate the atomic force microscope (AFM) cantilever by measuring its stiffness and deflection with quantifiable uncertainty. The AFM cantilever stiffness and deflection are measured with a calibrated microelectromechanical system (MEMS) device. The MEMS device is calibrated by electro-micro-metrology (EMM), which is an accurate and precise metrology technique that extracts mechanical properties through electrically probed measurands. Without precise and accurate measurements, reliable science is not possible. Precision is a measure of how tightly-spaced a cluster of data points are to each other, where tighter clusters imply better precision; and accuracy is a measure of distance between the average and true value, where smaller distances imply better accuracy. Since the AFM is widely used in nanoscience and nanoengineering for new discoveries and innovations, it is important that AFM measurements are both accurate and precise. There have been several efforts by others to calibrate the AFM; however, prior methods have yet to achieve an uncertainty smaller than 10%, which results in just one significant digit. For instance, several of these calibration methods are reviewed in [1]. What is different about our method is the significant reduction of uncertainty by the elimination of unknowns. Conversely, other techniques often involve the use of quantities that are either poorly measured, have large uncertainties, or found in a lookup table. In the full paper we will explain and demonstrate the calibration method and describe how accuracy is determined, how uncertainty is determined, and show how the method is both repeatable and reliable. [1] N. A. Burnham, X. Chen, C. S. Hodges, G. A. Matei, E. J. Thoreson, C. J. Roberts, M. C. Davies, and S. J. B. Tendler, "Comparison of calibration methods for atomic-force microscopy cantilevers", Nanotechnology 14, 2003, pp. 1-6.