SUPPLEMENTARY MATERIAL
Controllable growth of metallic nano-helices at room temperature conditions
José M. Caridad2, David McCloskey2, John F. Donegan2, Vojislav Krstić1,2*
1
Chair for Applied Physics, Department of Physics, Friedrich-Alexander-University
Erlangen-Nürnberg, Staudtstr. 7, 91058 Erlangen, Germany
2
School of Physics, CRANN and AMBER, Trinity College Dublin, College Green, Dublin
2, Ireland
Supplementary Figure 1
FIG. S1. (a) Regular-shaped and freestanding Ni nano-helices made with pre-patterned
substrate (dots) and the bi-layer heat-sink introduced in this work. (b) Regular-shaped
and freestanding Ag nano-helices made with pre-patterned substrate (dots) and the bilayer heat-sink introduced in this work. Ag nano-helices are not as regular as the Ni
counterpart since Ag has a higher surface diffusion length than Ni for a given
temperature. (c) Length test on Ni nano-helices. The structure starts to get more
deformed after ~ 500 nm height (total length of the helix ~ 1000 nm) due to a
combination of shadowing irregularities and surface diffusion effects.
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Supplementary Figure 2
FIG. S2. SEM image of Ni nano-helices under non-optimized growth on a transparent
substrate composed of SiO2 and a thin film (150 nm) of ITO as a heat-sink layer. Note
that this image was not taken at a normal angle with respect to the helical axis.
Supplementary Table S1
Sample
(Metal)
pitch, 𝑝
(nm)
diameter, 𝐷
(nm)
nano-helix
height, ℎ (nm)
no. of
turns, 𝑁
S1(Ni)
325 ± 9
169 ± 9
400 ± 20
1.23
S2 (Ni)
S3(Ni)
S4 (Ni)
S5 (Ni)
S6 (Ag)
S7 (Ag)
S8 (Ag)
S9 (Ag)
130 ± 6
128 ± 9
63 ± 6
128 ±10
130 ± 9
140 ± 11
127 ± 9
127 ± 10
102 ± 6
72 ± 9
59 ± 6
72 ± 7
75 ± 7
103 ± 9
72 ± 7
72 ± 6
242 ± 15
390 ± 16
234 ± 20
275 ± 15
300 ± 16
300 ± 13
268 ± 12
238 ± 11
1.86
3.04
3.70
2.3
2.3
2.1
2.11
1.88
Table S1 Structural helix parameters of the grown structures, showing a variation of
pitch and diameter below 10%.
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Optical activity measurements
The optical activity of the metallic nano-helices was acquired in transmission using a commercial
spectrometer with liquid nitrogen cooled CCD detector (Horiba Triax 180) to record the spectral
response of the sample in the range from 400 to 1000 nm. A Xe discharge lamp was used as a light
source and a linear polarizer and a Fresnel romb were inserted to produce circular right- or lefthanded polarized light, RHC and LHC respectively. The white light was focused on the sample
through a 20x NA=0.4 microscope objective and the areas of interest of the sample are selected
with a 2 axis variable slit installed in the set-up.
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