Supplementary Information
Application of three-dimensionally area-selective atomic layer
deposition for selectively coating the vertical surfaces of standing
nanopillars
Wenjing Dong1, Kenan Zhang1, Yun Zhang1, Tiaoxing Wei1, Yan Sun1, Xin Chen1&
Ning Dai1
1
National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics,
Chinese Academy of Sciences, Shanghai 200083, China
(a) Au
(b) Au+DAT+ALD
(c) Si+DAT+ALD
(d) ZnO on planar Si
Figure S1 SEM images and EDS analysis of the planar Si samples with different
processes: (a) planar Si after sputtering of Ti/Au (step 2 in Figure 1); (b) planar Si
after sputtering of Ti/Au, and then modification of
DAT SAMs and then ALD under
90 oC for 300 cycles, indicating that DAT can be used as molecular resist for ALD
under our deposition condition and no ZnO has formed on its surface; (c) planar Si
after immersing in DAT solution and then for ALD under 90 oC for 300 cycles, the
surface has been covered by ZnO which can also be proved by EDS. The results
suggested that self-assembled DAT monolayer on Au films can be used as molecular
resist and ALD will not happen on such surfaces, and for the areas with no Au
presented the ALD process will not be influenced. (d) The thickness of ZnO thin films
grown by ALD on planar Si substrate under 90 oC versus the number of ALD cycles,
the growth rate of ZnO under 90 oC is ~0.12 nm/cycle.
(a)
(b)
(c)
(d)
Figure S2. SEM images of Si nanorod arrays: (a) without modification, (b) after
deposition of Au, the horizontal surfaces are covered by compact Au films and the
vertical surfaces are covered by Au particles, (c) after removing the Au on vertical
surfaces, Au particles on the vertical surfaces have been removed and the Au films on
the horizontal surfaces remain, (d) with area-selectively deposited ZnO on the vertical
surfaces, the area-selective ALD can also realize on the sharp edges of the gathered
nanorods. It is worth noting that, for the Ti films on the vertical surfaces would also
be not so compact just like Au films, some of the Au particles may probably deposited
directly on Si substrate. Though there may be a very thin Si oxide layer in between,
but HF will not easily bring the Au particles away by corroding the thin SiO2 layer.
However, as the interaction between Au and Si is not very tight, Au will easily detach
with Si substrate once immersing in solutions. Consequently, the Au particles on the
vertical surfaces that were not removed by HF would detach from the Si substrate
during the formation of SAMs when they were immersed in the ethanol solution of
DAT for enough time.
(a)
(b)
Figure S3. SEM images of (a) the original Si stripes (step 1) and (b) stripes with only
horizontal surfaces coated with Au (step 2). Due to the Au particles at the upper edges
of the vertical surfaces were a little thicker than that at the other part of the walls and
some of them were linked with the thin film on the top, the borderlines between Au
and Si were not perfect after HF immersing, however, they will not affect the
area-selective ALD on vertical surfaces.
Figure S4. EDS elemental line scan of Si strips with both vertical and horizontal
surfaces covered by ZnO when no hydrophobic SAMs were used on the stripes. To
get more information of the surfaces, a low accelerating voltage of 10KV were used.
No sharp peaks on the edges in comparison with Figure 4b as all the surfaces were
uniformly coated by ZnO. Due to the detecting angle, the Zn/O signals were a little
lower at the bottom part. As the signals also involved some information of the
environment within the diffusion depth of the injected electrons, the Si signals on the
top were a little lower than at the bottom for the strips contain less Si than the
substrate.
(a)
(b)
(c)
Figure S5. SEM images of (a) 3D stripes and (b) nanorods with their vertical surfaces
selectively covered by 300 cycles and 250 cycles of ALD ZnO, respectively, the
edges of horizontal surfaces are partly covered by ZnO. (c) Schematics show the
area-selective ALD with increasing the number of ALD cycles.