Atomic Force Microscopy Utilizing SubAngstrom Cantilever Amplitudes

Abstract

A major problem of dynamic mode atomic force microscopy has been the necessity to employ relatively large amplitude of drive of the cantilever in the few Angstrom to the nm range to allow for sustaining self-excitation, and to obtain sufficient signal to noise ratio for frequency or amplitude shift measurement. The use of laser Doppler interferometery and super heterodyne signal processing has enabled clear atomic resolution imaging using subAngstrom cantilever amplitudes in the MHz regime. Due to the small amplitude, and the fact that the tip apex was always within the field of force gradient, long life of the tip was obtained, and frequency shift could more readily be interpreted as that coming from the short range forces.