Novel Image Restoration Method Using Spherical Nano-particles for Atomic Force Microscopy Topography Data Containing Tip-induced Distortions

Abstract

  The most common use of the SPM, especially AFM, is the topography imaging. Therefore, the establishment of accurate imaging of surface microstructures is strongly demanded. The most significant distortion in AFM image is induced by the tip shape whenever the sample surface contains features with aspect ratios comparable to the tip apex size. The acquired AFM image is a convolution or dilation between the tip shape and the sample topography. To restore the original profile, a numerical deconvolution or erosion procedure using a precise tip shape function is required. In this study, we propose a new technique for restoration of AFM images using certified particle size standards or standard nano-spheres. First, AFM topography images of the nano-spheres dispersed on flat substrates such as Si(001) wafers are taken. Then, tip shape function is determined by numerical calculation. Next, surface topography of unknown sample can be restored by using the experimentally determined tip shape function. Assuming that the nano-particles are perfect spheres, the tip shape function can be determined. The real surface topography of an unknown sample surface is dilated to the scanned surface topography image by the tip shape function. Therefore, it is possible to extract the most probable surface morphology from the observed AFM topography image using the tip shape function. The experimental demonstration was performed by using 100 nm diameter standard nanospheres.