blocks notwithstanding there are good examples of effective nanomanipulation
that have made this field progress.
Early reports on AFM-based nanomanipulation, which showed the feasibility of
such a process, appeared as far back as 1995 [92, 93]. Subsequent publications also
addressed the modeling and simulation of such a process and the issue of manipulation forces [94–97].
The process of nanomanipulation involves control of a number of forces. The
main two forces are the force of adhesion (F a
tp ) between the AFM tip and the adsorbate particle which will be manipulated and that between the particle and the
substrate (F a
ps ). These forces are mediated by the surface forces [98] and depend
on the formation of a meniscus on the substrate. While F a
ps stabilizes the particle
on the substrate, F a
tp makes the particle stick to the tip. The contact force between
the tip and the particle F c makes the particle move. The movement of the cantilever from its equilibrium position and the force constant of the cantilever determine
the contact force in turn. In addition, since the experiments are carried out in
ambient air, there are capillary forces between the tip and the particle as well as the
van der Waal forces between the tip and the particle and between the particle and
the substrate. It is the balance of these forces that determines the final dynamics of
the particle movement.
As a simple model we consider F a
tp A 4pR eff g sv and F a
ps A 4pR p g sv where
R t ¼ radius of curvature of the tip and R p ¼ radius of curvature of the particle and
R eff ¼ ð1=R t þ 1=R p Þ
À1 . g sv ¼ surface energy at the solid/vapor interface. In order
to move the particle from one place to another it is important to ensure (1) that the
particle does not adhere to the tip and also (2) that the component of the contact
force between the tip and the particle parallel to the surface (F
c
k ) is larger than the
force of friction so that the particle can be moved. As a rough estimate of the force
Fig. 21.17. Using an AFM tip to place a nanoparticle between two e-beam fabricated electrodes.
21.6 Use of Scanning Probe Microscopy in Nanomanipulation 717
that have made this field progress.
Early reports on AFM-based nanomanipulation, which showed the feasibility of
such a process, appeared as far back as 1995 [92, 93]. Subsequent publications also
addressed the modeling and simulation of such a process and the issue of manipulation forces [94–97].
The process of nanomanipulation involves control of a number of forces. The
main two forces are the force of adhesion (F a
tp ) between the AFM tip and the adsorbate particle which will be manipulated and that between the particle and the
substrate (F a
ps ). These forces are mediated by the surface forces [98] and depend
on the formation of a meniscus on the substrate. While F a
ps stabilizes the particle
on the substrate, F a
tp makes the particle stick to the tip. The contact force between
the tip and the particle F c makes the particle move. The movement of the cantilever from its equilibrium position and the force constant of the cantilever determine
the contact force in turn. In addition, since the experiments are carried out in
ambient air, there are capillary forces between the tip and the particle as well as the
van der Waal forces between the tip and the particle and between the particle and
the substrate. It is the balance of these forces that determines the final dynamics of
the particle movement.
As a simple model we consider F a
tp A 4pR eff g sv and F a
ps A 4pR p g sv where
R t ¼ radius of curvature of the tip and R p ¼ radius of curvature of the particle and
R eff ¼ ð1=R t þ 1=R p Þ
À1 . g sv ¼ surface energy at the solid/vapor interface. In order
to move the particle from one place to another it is important to ensure (1) that the
particle does not adhere to the tip and also (2) that the component of the contact
force between the tip and the particle parallel to the surface (F
c
k ) is larger than the
force of friction so that the particle can be moved. As a rough estimate of the force
Fig. 21.17. Using an AFM tip to place a nanoparticle between two e-beam fabricated electrodes.
21.6 Use of Scanning Probe Microscopy in Nanomanipulation 717