Determination of the Radii of Coated and Uncoated Silicon AFM Sharp Tips using Height Calibration Standard Grating and Nonlinear Regression Function

Abstract

AFM sharp tips have been used to characterize nanostructures and quantify the mechanical properties of the materials in several areas of research. The analytical results can show unpredicted errors if we do not know the exact values of the AFM tip radius. There are many techniques of in-situ measurements for determining the actual AFM tip radius but limited to uncoated tips. This paper presents an alternative and simple method to determine the radii of coated tips and the uncoated tip. The Pt-coated, Cr-Au coated, and Si uncoated tips were used to scan on the calibration standard grating in AFM contact mode with sub-nano loading to get the curved scan profile of the edge corner of the grating structure. The data points of the curved profile of each tip were fitted with the nonlinear regression function to estimate the curvature radius of the tip. The results show that the estimated radius of the coated tips is in the range of nominal values provided by the tip manufacturer while the estimated radius of the Si uncoated tip is bigger than the nominal radius due to tip blunting during the scan. However, this method yields an accurate estimate of the tip radius with the low value of root mean squared error from curve fitting results.