Akademik Veri Yönetim Sistemi
The Fourth Global Conference on Advanced Nanotechnology and Nanomaterials , Barcelona, İspanya, 19 - 20 Eylül 2024, cilt.1, sa.1, ss.1
Micro-cantilever flexural modes exhibit quite different deflection
sensitivities to tip-sample interaction forces near sample surfaces in Atomic
Force Microscopy (AFM) operations. Van der Waals forces act on the tips of AFM
micro-cantilevers externally driven under single- and multi-frequency
excitations at the separation distances below 20 nm. In numerical studies, the
tip-sample interaction force sensitivity significantly depends on multiple
factors such as excitation schemes, mechanical properties, and geometries of
micro-cantilevers. More interestingly, the tip radius significantly affects the
observable oscillation sensitivity to nonlinear Van der Waals forces. Considering
the tip radius effect, nonlinear dynamic models can be robustly used to predict
the behaviors of the micro-cantilever under heptamodal operations. The numerical
results indicate that the influence of tip radius on amplitude sensitivity at
the first flexural mode is quite larger for single-frequency excitations rather
than heptamodal-frequency excitations. As the tip radius increases, higher
phase shift responses ranging between 0 and 180 degrees are obtained on a wider
domain of separation distance. It is also worth mentioning that notable phase
shift sensitivity does not exist for heptamodal operations. Larger driving
forces at multiple eigenmode frequencies hinder variations in phase shift
responses. Additionally, the AFM micro-cantilever with the tip radius of 80 nm
exhibits much more frequency shift sensitivities for the lower separation
distances. Based on theoretical calculations, selecting a proper tip radius can
bring notable improvements in observable sensitivity to Van der Waals forces
under heptamodal-frequency experiments.