Carbon nanotubes: a promising standard for quantitative evaluation of AFM tip apex geometry.

The direct contact between tip and sample in atomic force microscopy (AFM) leads to demand for a quantitative knowledge of the AFM tip apex geometry in high-resolution AFM imaging and many other types of AFM applications like force measurements and surface roughness measurements. Given, the AFM tip apex may change continuously during measurements due to wear or during storage due to oxidation, it is very desirable to develop an easy and quick way for quantitative evaluation of AFM tip radius when necessary. In this study, we present an efficient method based on Zenhausern model (Scanning 14 (1992) 212) by measuring single-wall carbon nanotubes deposited on a flat substrate to reach this goal. Experimental results show the method can be used for routine quantitative evaluation of AFM tip apex geometry for tips with effective radii down to the nanometer scale.