of very localized redox reactions by running a current through a conductive AFM tip. UV light can be used to control this localized redox
process because it affects electron-hole pairs in a way that changes their
resistance to current flow. This means that a low-voltage current running
through the tip will be able to oxidize a surface only when UV light is
shined on the surface at the same time. This method can produce smooth
surface features with a height of about 40 nm and a lateral length of about
1 μm. Surface-destructive AFM is thus fairly flexible, but its use can be
limited by expense and low production speed.
Other nanolithographic techniques that use AFM may be termed “constructive” because they build up the intended structure on the surface. As
with destructive AFM nanolithography, there are several different possible implementations. A common constructive method is the use of AFM
as a “dip pen.” The AFM tip is covered in some molecule to be used as
“ink,” which is then deposited on the surface at the meniscus between the
tip and the surface. A resolution below 50 nm is currently possible with
dip-pen methods.
Metals can be transferred to the tip by applying pressure to the tip on a
metal surface, heating it, and allowing it to cool. The substance can be
transferred from the tip to a surface by reheating the tip as it is dragged
over the surface. Using this technique with indium has been successful in the creation of conductive nanoscale wires, with widths as low as
50 nm.
There are many different molecules that can be used as ink for this
method, giving a great deal of flexibility in its uses for surface patterning.
For example, a surface can be patterned with chemicals that will protect it
against a later etching treatment, allowing for an interesting combination
of constructive and destructive lithographic techniques to make more
complex patterns. Another possible use of this method is the patterned
deposition of particles that can act as “seeds” for new pattern creation,
either by catalyzing reactions or by binding to other molecules with
interesting shapes that form the basis for a new pattern.
An advantage of dip-pen nanolithography is that the technique can also
be scaled up by using an array of several AFM tips instead of just one,
allowing something analogous to desktop printer functionality for
nanofabrication. Using an array of tips would allow for the creation of
patterns at greater speeds and over larger areas. This has shown great
potential for the use of AFM in the creation of nanoscale electronic
components such as transistors.
CHAPTER 10: Fabrication, Properties, and Applications of Thin Films
418
process because it affects electron-hole pairs in a way that changes their
resistance to current flow. This means that a low-voltage current running
through the tip will be able to oxidize a surface only when UV light is
shined on the surface at the same time. This method can produce smooth
surface features with a height of about 40 nm and a lateral length of about
1 μm. Surface-destructive AFM is thus fairly flexible, but its use can be
limited by expense and low production speed.
Other nanolithographic techniques that use AFM may be termed “constructive” because they build up the intended structure on the surface. As
with destructive AFM nanolithography, there are several different possible implementations. A common constructive method is the use of AFM
as a “dip pen.” The AFM tip is covered in some molecule to be used as
“ink,” which is then deposited on the surface at the meniscus between the
tip and the surface. A resolution below 50 nm is currently possible with
dip-pen methods.
Metals can be transferred to the tip by applying pressure to the tip on a
metal surface, heating it, and allowing it to cool. The substance can be
transferred from the tip to a surface by reheating the tip as it is dragged
over the surface. Using this technique with indium has been successful in the creation of conductive nanoscale wires, with widths as low as
50 nm.
There are many different molecules that can be used as ink for this
method, giving a great deal of flexibility in its uses for surface patterning.
For example, a surface can be patterned with chemicals that will protect it
against a later etching treatment, allowing for an interesting combination
of constructive and destructive lithographic techniques to make more
complex patterns. Another possible use of this method is the patterned
deposition of particles that can act as “seeds” for new pattern creation,
either by catalyzing reactions or by binding to other molecules with
interesting shapes that form the basis for a new pattern.
An advantage of dip-pen nanolithography is that the technique can also
be scaled up by using an array of several AFM tips instead of just one,
allowing something analogous to desktop printer functionality for
nanofabrication. Using an array of tips would allow for the creation of
patterns at greater speeds and over larger areas. This has shown great
potential for the use of AFM in the creation of nanoscale electronic
components such as transistors.
CHAPTER 10: Fabrication, Properties, and Applications of Thin Films
418