Program and Abstract Book - SRON

19 th International Symposium on Space Terahertz Technology
Experimental detection of terahertz radiation in bundles of single wall carbon
nanotubes
K.S. Yngvesson, K. Fu, R. Zannoni, C. Chan, S.H.Adams, J. Nicholson, and E. Polizzi
Department of Electrical and Computer Engineering, University of Massachusetts, Amherst, MA 01003, USA
11-1
We report the experimental detection of
terahertz radiation at five frequencies from 0.69
THz to 2.54 THz in devices consisting of bundles
of carbon nanotubes, containing metallic single
wall carbon nanotubes (m-SWNTs). The CNTs
are quasi-optically coupled through a
lithographically fabricated antenna, and a silicon
lens. The measured data are consistent with a
bolometric detection process in the m-SWNTs
and the devices show promise for operation well
above 4.2 K. The maximum responsivity at
present is about 10 V/W but analysis shows how
this may be increased by two to three orders of
magnitude in the future.
Itkis et al. [1] have reported a sensitive
bolometric Near Infrared detector based on a
Carbon Nanotube (CNT) film. Microwave
detection using CNT Schottky barriers, CNT-
FETs and CNT bundles has been extended to 110
GHz [2]. The question thus arises whether
SWNTs could be useful as terahertz detectors, as
we proposed in [3]. We reported microwave
detection in single m-SWNTs at a previous
ISSTT [4]. For the present work we have
fabricated bundles containing m-SWNT devices
by the Dielectrophoresis (DEP) method. We
performed microwave measurements on CNTs
contacted to CPWs and terahertz measurements
on CNTs coupled to a log-periodic antenna, the
latter with an 8 μm gap. The terahertz source was
a gas laser. Each metallic SWNT tube is assumed
to be modeled by the equivalent circuit
introduced and analyzed by P. Burke [5] based
on which we estimated the average coupling loss
to be 12 dB. It is significant that the microwave
measurements indicate a large enough contact
capacitance that effectively shunts the contact
resistance at terahertz frequencies.
Our hypothesis is that the detection process
at terahertz frequencies is of the bolometric type,
similar to that in ref. [1], in contrast with the
diode-like detection mechanism at microwaves
[4]. To support this hypothesis we have
measured the temperature-dependence of the
device resistance. When using this data to predict
the voltage responsivity as a function of bias
voltage we find very good agreement. The CNT
bolometer then effectively is similar to a phononcooled
HEB, that potentially has a shorter
thermal time constant than superconducting
HEBs.
Ab initio simulations are also being
performed to model contact and transport effects
in the CNTs. Preliminary results of these
simulations have been published in [6].
Future work will concentrate on improved
fabrication and simulation methods for m-SWNT
devices, optimizing the device coupling, and
demonstration of heterodyne detection.
This work was supported by NSF grants ECS-
0508436 and ECS-0725613.
References
[1] M.E. Itkis, F. Borondics, A. Yu and R.C.
Haddon, Science, 312, 413 (2006).
[2] M. Tarasov, J. Svensson, L. Kuzmin, and E.
E. B. Campbell, Appl. Phys. Lett., 90, 163503
(2007).
[3] K.S. Yngvesson, Appl. Phys. Lett. 87,
043503 (2005).
[4] K.S. Yngvesson et al., 17th ISSTT, Paris,
France, May 2006.
[5] P.J. Burke, IEEE Trans. Nano Technol. 1,
129 (2002).
[6] D. Zhang and E. Polizzi, J. Comp.
Electronics, 2007, accepted.
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