Quantitative atom-resolved force gradient imaging using noncontact atomic force microscopy

Abstract

Quantitative force gradient images are obtained using a sub-angström amplitude, off-resonance lever oscillation method during scanning tunneling microscopy imaging. We report the direct observation of short-range bonds, and the measured short-range force interaction agrees well in magnitude and length scale with theoretical predictions for single bonds. Atomic resolution is shown to be associated with the presence of a prominent short-range contribution to the total force interaction. It is shown that the background longer-range interaction, whose relative magnitude depends on the tip structure, has a significant effect on the contrast observed at the atomic scale. © 2001 American Institute of Physics

Measurement of energy dissipation between tungsten tip and Si(1 0 0)-(2×1) using sub-Ångström oscillation amplitude non-contact atomic force microscope

“…Measurement of tip-sample forces and dissipation of energy as a function of separation [5][6][7] is also possible and will probably shed light into a number of interesting problems like atomic manipulation, atomic scale friction, etc. We have recently built a highly sensitive nc-AFM using small oscillation amplitudes (0.25 Å ) [8] for imaging [9][10][11] and force/dissipation-distance spectroscopy [12]. Employment of sub-Å ngström oscillation amplitudes has a number of advantages over large oscillation amplitudes used by most of other groups and simplifies the analysis considerably.…”

Sub-Angstrom oscillation amplitude non-contact atomic force microscopy for lateral force gradient measurement

“…Simultaneous lateral stiffness and STM topography images on Si(1 1 1)-(7 Â 7) surface are obtained. We also present the direct measurement of lateral forces as we vary the tip-sample separation, similar to our earlier experiments using ultra small amplitude non-contact AFM/STM [12][13][14][15] in normal forces.…”

“…The microscope employs a sensitive fibre optic interferometer [12] for high force resolution. Sub-Angstrom oscillation amplitudes can be used for imaging as well as performing direct lateral force-distance spectroscopy.…”

Small‐Amplitude Atomic Force Microscopy

“…Since first experiments with small amplitude AFM in 1993, [33] this technique has been successfully used to measure chemical bonding forces, [34,35] few-atom contact mechanics, [20,35] atomic-scale dissipation, [20] and to achieve atomic [36] and sub-atomic [11] resolution in ultra-high vacuum, as well as to investigate molecular ordering [37] and nanotribology in liquids, including water. [38] 2.…”