Biomedical Engineering Reference
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surface. By using this technique, organic monolayers can be directly
written on the surface with no additional steps, and multiple inks
can be used to write different molecules on the same surface. By
coupling electrochemical techniques, the DPN are not limited to
deliver organic molecules to the surface. Electrochemical “dip-
pen” nanolithography (EC-DPN) technique can be used to directly
fabricate metal and semiconductor nanostructures on surfaces.
Figure 1.4
Schematic sketch of the EC-DPN experimental setup.
The tiny water meniscus on the AFM tip was used as a nano-
sized electrochemical cell, in which metal salts can be dissolved,
reduced into metals electrochemically and deposit on the surface
as shown in Fig. 1.4. In a typical experiment, an ultrasharp silicon
cantilever coated with H
is scanned on a cleaned p-type Si
(100) surface with a positive DC bias applied on the tip. During
this lithographic process, H
PtCl
6
2
dissolved in the water meniscus
is electrochemically reduced from Pt(IV) to Pt(0) metal at the
cathodic silicon surface and deposits as Pt nano-features as shown
in Fig. 1.
5
[106].
PtCl
2
6
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