Improvement in uncertainty of tuning fork-based force sensor stiffness calibration via the indentation method using direct determination of contact and machine compliance

Abstract

Noncontact-atomic force microscopy (NCAFM) combines atomic resolution imaging with the ability to measure forces at the atomic scale. Despite burgeoning applications for this method to measure force at the atomic scale, the metrology necessary to interpret the frequency shifts occurring in NCAFM sensors from tip-sample interactions is still in a very early stage of development. A key parameter in this measurement is the stiffness of the sensor being used in the measurement. Here we outline an improvement in the procedure for measuring the spring constant of a tuning fork-type sensor using an instrumented indenter. Instead of using models and materials properties to estimate the effect of contact and machine compliance, these quantities are directly measured by indenting the base of the tuning fork. This decreases the uncertainty in the measurement by nearly a factor of two. © The Society for Experimental Mechanics, Inc. 2014.