Calibration of Atomic Force Microscope Tips Using Biomolecules

Atomic force microscope (AFM) images of surfaces and samples mounted on substrates are subject to artifacts such as broadening of structures and ghost images of tips due to the finite size and shape of the contacting probe. Therefore, knowledge of the radius of the AFM probe tip is essential for the interpretation of images. We have deduced the shape of the AFM tip by imaging cylindrical biological molecules of various diameters such as deoxyribonucleic acid (DNA), tobacco mosaic virus (TMV), tobacco etch virus (TEV) and bacteriophage M-13 (M-13). Using a paraboloidal tip model and numerically solving equations of contact, the curvatures of the tip and lithographically sharpened tip were ascertained.