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Appl. Phys. Lett., Vol. 78, No. 19, 7 May 2001
Djenizian, Santinacci, and Schmuki
lead to more satisfactory results than longer exposure at less
cathodic values. This is consistent with a 3D island growth
mode and a Volmer–Weber approach, suggesting a higher
number of activation sites being triggered with a higher ov-
ervoltage. This leads to a coalescence of islands in an earlier
growth stage, and thus a finer grain size, and to a higher
achievable lateral resolution.
The principle demonstrated in this work should be appli-
cable to essentially a large palette of materials that can be
electrodeposited from an aqueous environment ͑such as met-
als, semiconductors, polymers͒. Therefore, this technique
may be employed to create patterned surfaces of a wide
range of materials with a lateral resolution in the 100 nm
range. Additionally, the principle bears the potential to be
used on any conductive substrate and thus to be useful to
locally functionalize different substrate materials.
FIG. 3. SEM image of a 70 nm wide gold line between two masking C
lines. Au deposition was carried out in 10 mM KAu͑CN͒ ϩ1 M KCN by a
2
potential step to Ϫ1.6 V ͑Ag/AgCl͒ for 10 s.
semiconductor surface is typically weak and hence the depo-
sition follows a 3D-island growth mechanism21 and the
growth kinetics can be described in terms of the Volmer–
The authors would like to acknowledge the Swiss Na-
tional Science Foundation for financial support of this work.
For help with the experiments the authors would like to
thank Nicolas Xanthopoulos ͑EPFL͒ for AES measurements.
2
2
Weber approach. This implies that the number of success-
fully triggered nucleation sites for growing a metal cluster is
potential dependent. In order to grow a coherent film with a
maximum local resolution it is desired to trigger as high as
possible number of initiation sites. This leads to coalescence
of deposit island in an early growth state ͑small feature size͒
and therefore improves the resolution of the deposition pro-
cess. ͑If the size of the nuclei becomes large compared with
the spacing between masking carbon lines, the crystallite size
limits the lower resolution of the process.͒ According to the
Volmer–Weber approach, the density of nuclei increases
also with time. However, as the size distribution of clusters
triggered early and late in the process becomes wide and
diffusion phenomena become increasingly important with
time, it is clearly preferable to achieve coalescence of islands
by a high potential/short exposure time parameter combina-
tion than by a low potential/long exposure time combination.
In summary, the results clearly demonstrate that electron
beam-induced C masking of a semiconductor surface can be
exploited for a subsequent selective electrochemical metal
deposition in the submicrometer range.
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Ϫ6
the pressure range of 3ϫ10 mbar, C masks of a thickness
1
1
2
2
8
9
0
1
of less than one nanometer can be produced. Even this low
layer thickness can be sufficient to efficiently and selectively
block charge transfer with the electrolyte and thus prevent a
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22
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