Temperature-dependent diffusive to ballistic transport transition in
aligned double walled carbon nanotubes in the high frequency regime
George Chimowa, E. Flahaut and Somnath Bhattacharyya
Supplementary Material
Preparation of CNTs device involves the processes illustrated in Fig. S1 below: Schematic
diagram of the whole fabrication process of the devices and the measurement set up. It
consists of CNT alignment using dielectrophoresis.
(b) Nano-manipulation
(a) Dielectrophoresis
~ AC 1 V p-p
10 Mhz
(c) Bonding
G.I.S
(d) HF Measurements
ebe
a
m
G.
S.
G
Pr
o
b
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G.
S.
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Figure S1. (a), CNT selection using nano-manipulators (b) and CNT metal contact bonding
using a combination of e-beam lithography and gas injection system (GIS) (c). The HF
impedance is then measured using G-S-G probes with a 50 µm pitch size (d).
Figures [S2 (a), (b), (c)] below show SEM and TEM images of nanotubes aligned across the
gap of a coplanar waveguide.
(c)
(d)
Figure S2. SEM micrograph for DW2 (a) had eleven DWNTs but because of the scale only a few
can be seen, DW1 (b) had four on separate positions as shown. (c–d) TEM micrographs DWNTs
networks after catalyst removal and before alignment, showing good quality CNTs either isolated
or forming small-diameter bundles.
The extra data given in this section shows the rigorous test done to ensure measurement
(shown in Fig. S3 and S4) accuracy as outlined in the paper. Fig. S4 indicates that the solvent
that was used to disperse the CNTs does not affect the measurement accuracy. The inset
illustrates the reproducibility of the data and the care practiced to ensure that the probe
contact force is maintained the constant. This was made easier by the probe’s graduated
screw-gauges used to lower them down. Average error over the entire spectrum = 0.027 dB
-20
Mag S12 (dB)
-30
MW9 A
MW9 B
-40
Checking
drift
CheckingInstrumement
Instrument Drift
-50
-60
0
10
20
30
40
50
60
Frequency (GHz)
Figure S3. S - parameter data for a MWNT sample 9 measured at different times. MW9 B
was measured 30 minutes after MW 9 A. It clearly shows that there is insignificant
instrument drift with time. The above given data shows that the measurement done on the
samples are very much reproducible with negligible instrument drift affecting the result. It
further shows the accurate precise placements of the probe tips on the sample half an hour
later. Average error in the entire spectrum = 0.03 dB
-22
Open
Control
-24
-18
Reproducibility test
-20
Mag S12 (dB)
Mag S12 (dB)
Checking effect of solvent
-26
-22
-26
20
-28
MW9
MW9B
MW10
MW10B
-24
30
40
50
Frequency (GHz)
20
30
40
50
Frequency (GHz)
Figure S4: Shows the test done to check the effect of solvent on the S-parameter
measurement. The - Open data is for an open dummy waveguide with dichlorobenzene the
solvent used dispersed on the one micron gap. And the - Control is for the same dummy
without the solvent. Inset: Shows the test to check measurement reproducibility MWNT
samples 9 and 10 were measured repeatedly every time lifting up the probes. The graph
shows very good reproducibility.