A novel method for surface coverage spectroscopy with atomic force microscope: theory, modeling and experimental results for cylindrical nanostructures

Abstract

A novel method for measuring the surface coverage of randomly distributed cylindrical nanoparticles such as nanorods and nanowires, using atomic force microscopy (AFM), is presented. The method offers several advantages over existing techniques such as particle beam and x-ray diffraction spectroscopy. These include, subnanometer vertical and lateral resolution, non destructive interaction with the sample surface allowing repeated measurements, user-friendly setup and ambient operating conditions. The method relies on the use of a statistical model to describe the variations of the nanoparticles aggregates height as a function of x,y position on the sample surface measured by AFM. To verify the validity of the method we studied two types of randomly oriented networks of carbon nanotubes (CNTs) and silver nanowires (Ag NWs) both processed from solution phase. Experimental results are found to be in excellent agreement with model predictions whilst analysis of the measured surface height density, together with the nanoparticle diameter statistical distribution, allow the extraction of the coverage coefficients for all detected nanoparticle aggregates as well as for the total surface coverage. The method can be seen as a new powerful tool for the quantitative surface coverage analysis of arbitrary nanoscale systems.