We have constructed a noise measurement setup for high impedance carbon
nanotube samples. Our setup, working in the frequency range of 600 - 900 MHz,
takes advantage of the fact that the shot noise power is reasonably large for
high impedance sources so that relatively large, fixed non-matching conditions
can be tolerated.Comment: 2 pages, 2 figures, published on AIP conference proceedings 200

Hakonen, Pertti

Paalanen, Mikko

Roschier, Leif

Tsuneta, Taku

Wang, Taihong

Wu, Fan

English

arXiv

Fan Wu

Leif Roschier

Taku Tsuneta

Mikko Paalanen

Taihong Wang

Pertti Hakonen

Crossref

This is an electronic reprint of the original article.
This reprint may differ from the original in pagination and typographic detail.
Author(s): Wu, F. & Roschier, L. & Tsuneta, T. & Paalanen, M. & Wang, T. H. &
Hakonen, Pertti J.
Title: Setup for shot noise measurements in carbon nanotubes
Year: 2006
Version: Final published version
Please cite the original version:
Wu, F. & Roschier, L. & Tsuneta, T. & Paalanen, M. & Wang, T. H. & Hakonen, Pertti J.
2006. Setup for shot noise measurements in carbon nanotubes. 24th International
Conference on Low Temperature Physics. AIP Conference Proceedings. 850.
1482-1483. ISBN 0-7354-0347-3 (printed).
Rights: © 2006 AIP Publishing. Copyright of AIP Conference Proceedings is the property of American Institute of
Physics and its content may not be copied or emailed to multiple sites or posted to a listserv without the
copyright holder's express written permission. However, users may print, download, or email articles for
individual use.
All material supplied via Aaltodoc is protected by copyright and other intellectual property rights, and
duplication or sale of all or part of any of the repository collections is not permitted, except that material may
be duplicated by you for your research use or educational purposes in electronic or print form. You must
obtain permission for any other use. Electronic or print copies may not be offered, whether for sale or
otherwise to anyone who is not an authorised user.
Powered by TCPDF (www.tcpdf.org)
Setup for shot noise measurements in carbon nanotubes 
Fan Wu*, Leif Roschier*, Taku Tsuneta*, Mikko Paalanen*, Taihong Wang1* and 
Pertti Hakonen* 
*Low Temperature Laboratory, Helsinki University of Technology, P.O. Box 2200, 02015 TKK, Finland 
^Institute of Physics, Chinese Academy of Sciences, Beijing 100080, China 
Abstract. We have constructed a noise measurement setup for high impedance carbon nanotube samples. Our setup, working 
in the frequency range of 600 - 900 MHz, takes advantage of the fact that the shot noise power is reasonably large for high 
impedance sources so that relatively large, fixed non-matching conditions can be tolerated. 
Keywords: Carbon nanotubes, microwave frequency, shot noise 
PACS: 73.23.-b,73.23.Hk, 85.25.Cp 
Noise measurements in out-of-equilibrium conditions 
can be employed to acquire extra information on top 
of that obtained from ordinary conductance measure-
ments, the data of which are related to equilibrium noise 
by the fluctuation dissipation theorem. Such noise mea-
surements, however, are hindered by the ubiquitous 1/f 
noise, in respect to which carbon nanotube devices make 
no exception[l —9]. Collins et al. measured \lf noise 
of several samples of single-walled nanotubes (SWNT), 
and found them to be so noisy that their use as electronic 
components is compromisedfl], at least at room temper-
ature. On the contrary, extremely good low-frequency 
noise properties have been achieved for single electron 
transistors made out of multiwalled carbon nanotubes 
(MWNT) by Roschier et al. [2]. 
Altogether, on the basis of the noise measurements 
performed so far, it has become apparent that standard 
low-noise experimental techniques, reaching only up to 
10 kHz due to RC cut-off problems, are not sufficient to 
study shot noise phenomena in carbon nanotubes. One 
approach to circumvent the limitations due to RC cut-off 
is to use resonant techniques to compensate the lead ca-
pacitance. Alternatively, microwave techniques with im-
pedance matching may be employed. Both methods call 
for high-frequency, low temperature amplifiers, working 
in either the MHz or even the GHz regime. Our new noise 
measurement setup employs microwave techniques but 
differs slightly from the standard solution by allowing 
for unmatching conditions for the sample. 
The heart of our setup is a cooled, home-made HEMT 
preamplifier that operates in the frequency range of range 
of 600 - 950 MHz[10]. The average noise temperature 
of this low-noise amplifier (LNA) over the measure-
ment bandwidth of 600-900 MHz is about 4 K. Under 
strong unmatching conditions, the back action noise of 
the preamplifier is fully reflected back to the amplifier, 
independent of the sample impedance, and therefore this 
G = 70dB 
RFIN 
FIGURE 1. Principle of the shot noise measurement setup. 
A microwave frequency switch is employed to select either 
the studied object or a tunnel junction noise source. The noise 
integrated over the bandwidth 600 - 900 MHz is read either 
from the output of the Schottky diode detector or from the 
output of the lock-in amplifier if AC-modulation of current is 
applied. For further details, see text. 
gives only a constant shift in the level of integrated noise 
at the output. The setup is illustrated in Fig. 1. 
The main goal in our setup is to measure reliably the 
Fano-factor F which relates the measured noise Sj to 
the full shot noise 2e < I > of a Poissonian process: 
F = Si/(2e < I > ) , where < / > is the average current. 
This is a characteristic number for mesoscopic samples 
in general [11]. The Fano-factor is connected to quantum 
partition noise, which for a single transport channel is 
given by 
< ( < 5 / ) 2 > = 2 e < / > ( l - T ) , (1) 
where transmission coefficient is denoted by T. In a 
multichannel system, sum over the transmission channels 
is taken. For example, for a mesoscopic diffusive wire, 
one obtains F = 1/3 without interaction or hot electron 
effects. For a tunnel junction, F = 1. In fact, by having a 
CP850, Low Temperature Physics: 24th International Conference on Low Temperature Physics; 
edited by Y. Takano, S. P. Hershfield, S. O. Hill, P. J. Hirschfeld, and A. M. Goldman 
© 2006 American Institute of Physics 0-7354-0347-3/06/$23.00 
1482 
high impedance tunnel junction and a microwave switch, 
this latter fact is employed to calibrate the sensitivity of 
our noise setup. 
In our setup, bias-tees are used to allow voltage bias-
ing of the sample and to measure the IV-characteristics 
while the noise measurement at microwave frequencies 
is going on. The amplification by the 4.2 K amplifier en-
hanced by three room-temperature amplifiers in series in 
order to make the signal level sufficient for a Schottky-
diode power detector. Band width limitation is employed 
before the detector in order to cut off the extra noise due 
to the rather wide band width of the room temperature 
amplifiers (6 GHz for MITEQ SMC03 and 20 GHz for 
SMC05). Small AC-modulation is typically applied on 
top of the DC-bias so that drift in the noise level is elim-
inated by using lock-in techniques after detection. The 
full noise can then be obtained by numerical integration. 
This scheme, however, does not eliminate the drift in the 
gain of the amplifiers. Temperature stabilization of the 
LNAs, especially the room temperature ones, has been 
found to decrease this drift substantially. 
The noise power of a source having an impedance R is 
given by 
eV 
Pnoise = SiR = 4kBT(l -F) + F2eIRcoth — . (2) 
KBI 
This formula shows that the thermal noise and the shot 
noise are intermixed in a manner depending on the Fano-
factor, which makes a separation of the contributions of 
thermal and shot noise complicated. Since the pream-
plifier is matched to a transmission line having the im-
pedance of Zo = 50 Q, the coupling from the source to 
the preamplifier is governed by the mismatch between 
the transmission line and the source. This is governed by 
reflection coefficient T = (R — ZQ)/{R — Zo) in which R 
denotes the small-signal resistance of the sample at the 
operating point. Thus, the noise power Pmeasure coupled 
to the preamplifier becomes 
Pmeasure = Pnoise(l ~ \T\2) ~ FSeIZ0j (3) 
where the latter form is valid in the regime FeV » RBT. 
Therefore, for samples with only weakly non-linear IV-
curves, the Fano factor can be obtained directly as the 
ratio of the slopes of the noise vs. current curves mea-
sured for the tunnel junction and the nanotube samples. 
Fig. 2 illustrates the resolution achieved on a tunnel 
junction sample of resistance RT = 7.7 kQ. The signal to 
noise ratio is clearly so good that the main limitation of 
our method comes from the requirement of FeV »ksT. 
As worked out by Spietz et al [12], the cross-over regime 
between thermal and shot noise can be employed to 
determine absolute temperature of the sample, and by 
using the fitted lines we get T = 4.2 K as expected. 
- 8 - 6 - 4 - 2 0 2 4 6 8 
V(mV) 
FIGURE 2. Noise vs. bias current measured on a tunnel 
junction with RT = 7.7 kQ. The tunnel junction was made of 
A1/A10X/A1 using standard two-angle shadow evaporation. 
ACKNOWLEDGMENTS 
It is a pleasure to thank T. Lehtinen, L. Korhonen, M. 
Sillanpaa, and R. Tarkiainen for valuable help. This 
work was supported by Academy of Finland, and by the 
Vaisala foundation. 
REFERENCES 
1. P. G. Collins, M. S. Fuhrer, and A. Zettl, Appl. Phys. Lett. 
76, 894 (2000). 
2. L. Roschier, R. Tarkiainen, M. Ahlskog, M. Paalanen, and 
P. Hakonen, ,4/?/?/. Phys. Lett. 78, 3295 (2001). 
3. M. Ahlskog, R. Tarkiainen, L. Roschier, and P. Hakonen, 
Appl. Phys. Lett. 11, 4037 (2000). 
4. H. W. Ch. Postma, T. F. Teepen, Z. Yao, and C. Dekker, 
in Electronic Correlations: from meso- to nanophysics, 
Proc. XXXVIth Rencontres de Moriond, ed. by T. Martin, 
G. Montambaux, and J. Tran Thanh Van, EPD Sciences, 
France, 2001, pp. 433-436. 
5. P.-E. Roche, M. Kociak, S. Gueron, A. Kasumov, B. 
Reulet, and H. Bouchiat, Eur. Phys. J. B 28, 217 (2002). 
6. H. Ouacha, M. Willander, H. Y. Yu, Y W. Park, M. S. 
Kabir, S. H. M. Persson, L. B. Kish, and A. Ouacha, Appl. 
Phys. Lett. 80, 1055 (2002). 
7. E. S. Snow, J. P. Novak, M. D. Lay, and F. K. Perkins, 
Appl. Phys. Lett. 85, 4172 (2004). 
8. R. Vajtai, B. Q. Wei, Z. J. Zhang, Y Jung, G. Ramanath, 
and P. M. Ajayan, Smart Mater. Struct. 11, 691 (2002). 
9. R. Tarkiainen, L. Roschier, M. Ahlskog, M. Paalanen, and 
P. Hakonen, Physica E 28, 57 (2005). 
10. L. Roschier and P. Hakonen, Cryogenics, 44,783 (2004). 
11. Ya.M. Blanter, M. Biittiker, Phys. Rep. 336, 1 (2000). 
12. L. Spietz, K. W. Lehnert, I. Siddiqi, and R. J. Schoelkopf, 
Science 300, 1929(2003). 
1483 



Setup for shot noise measurements in carbon nanotubes

This is an electronic reprint of the original article.This reprint may differ from the original in pagination and typographic detail.Author(s): Wu, F. & Roschier, L. & Tsuneta, T. & Paalanen, M. & Wang, T. H. &Hakonen, Pertti J.Title: Setup for shot noise measurements in carbon nanotubesYear: 2006Version: Final published versionPlease cite the original version:Wu, F. & Roschier, L. & Tsuneta, T. & Paalanen, M. & Wang, T. H. & Hakonen, Pertti J.2006. Setup for shot noise measurements in carbon nanotubes. 24th InternationalConference on Low Temperature Physics. AIP Conference Proceedings. 850.1482-1483. ISBN 0-7354-0347-3 (printed).Rights: © 2006 AIP Publishing. Copyright of AIP Conference Proceedings is the property of American Institute ofPhysics and its content may not be copied or emailed to multiple sites or posted to a listserv without thecopyright holder's express written permission. However, users may print, download, or email articles forindividual use.All material supplied via Aaltodoc is protected by copyright and other intellectual property rights, andduplication or sale of all or part of any of the repository collections is not permitted, except that material maybe duplicated by you for your research use or educational purposes in electronic or print form. You mustobtain permission for any other use. Electronic or print copies may not be offered, whether for sale orotherwise to anyone who is not an authorised user.Powered by TCPDF (www.tcpdf.org)Setup for shot noise measurements in carbon nanotubes Fan Wu*, Leif Roschier*, Taku Tsuneta*, Mikko Paalanen*, Taihong Wang1* and Pertti Hakonen* *Low Temperature Laboratory, Helsinki University of Technology, P.O. Box 2200, 02015 TKK, Finland ^Institute of Physics, Chinese Academy of Sciences, Beijing 100080, China Abstract. We have constructed a noise measurement setup for high impedance carbon nanotube samples. Our setup, working in the frequency range of 600 - 900 MHz, takes advantage of the fact that the shot noise power is reasonably large for high impedance sources so that relatively large, fixed non-matching conditions can be tolerated. Keywords: Carbon nanotubes, microwave frequency, shot noise PACS: 73.23.-b,73.23.Hk, 85.25.Cp Noise measurements in out-of-equilibrium conditions can be employed to acquire extra information on top of that obtained from ordinary conductance measure-ments, the data of which are related to equilibrium noise by the fluctuation dissipation theorem. Such noise mea-surements, however, are hindered by the ubiquitous 1/f noise, in respect to which carbon nanotube devices make no exception[l —9]. Collins et al. measured \lf noise of several samples of single-walled nanotubes (SWNT), and found them to be so noisy that their use as electronic components is compromisedfl], at least at room temper-ature. On the contrary, extremely good low-frequency noise properties have been achieved for single electron transistors made out of multiwalled carbon nanotubes (MWNT) by Roschier et al. [2]. Altogether, on the basis of the noise measurements performed so far, it has become apparent that standard low-noise experimental techniques, reaching only up to 10 kHz due to RC cut-off problems, are not sufficient to study shot noise phenomena in carbon nanotubes. One approach to circumvent the limitations due to RC cut-off is to use resonant techniques to compensate the lead ca-pacitance. Alternatively, microwave techniques with im-pedance matching may be employed. Both methods call for high-frequency, low temperature amplifiers, working in either the MHz or even the GHz regime. Our new noise measurement setup employs microwave techniques but differs slightly from the standard solution by allowing for unmatching conditions for the sample. The heart of our setup is a cooled, home-made HEMT preamplifier that operates in the frequency range of range of 600 - 950 MHz[10]. The average noise temperature of this low-noise amplifier (LNA) over the measure-ment bandwidth of 600-900 MHz is about 4 K. Under strong unmatching conditions, the back action noise of the preamplifier is fully reflected back to the amplifier, independent of the sample impedance, and therefore this G = 70dB RFIN FIGURE 1. Principle of the shot noise measurement setup. A microwave frequency switch is employed to select either the studied object or a tunnel junction noise source. The noise integrated over the bandwidth 600 - 900 MHz is read either from the output of the Schottky diode detector or from the output of the lock-in amplifier if AC-modulation of current is applied. For further details, see text. gives only a constant shift in the level of integrated noise at the output. The setup is illustrated in Fig. 1. The main goal in our setup is to measure reliably the Fano-factor F which relates the measured noise Sj to the full shot noise 2e < I > of a Poissonian process: F = Si/(2e < I > ) , where < / > is the average current. This is a characteristic number for mesoscopic samples in general [11]. The Fano-factor is connected to quantum partition noise, which for a single transport channel is given by < ( < 5 / ) 2 > = 2 e < / > ( l - T ) , (1) where transmission coefficient is denoted by T. In a multichannel system, sum over the transmission channels is taken. For example, for a mesoscopic diffusive wire, one obtains F = 1/3 without interaction or hot electron effects. For a tunnel junction, F = 1. In fact, by having a CP850, Low Temperature Physics: 24th International Conference on Low Temperature Physics; edited by Y. Takano, S. P. Hershfield, S. O. Hill, P. J. Hirschfeld, and A. M. Goldman © 2006 American Institute of Physics 0-7354-0347-3/06/$23.00 1482 high impedance tunnel junction and a microwave switch, this latter fact is employed to calibrate the sensitivity of our noise setup. In our setup, bias-tees are used to allow voltage bias-ing of the sample and to measure the IV-characteristics while the noise measurement at microwave frequencies is going on. The amplification by the 4.2 K amplifier en-hanced by three room-temperature amplifiers in series in order to make the signal level sufficient for a Schottky-diode power detector. Band width limitation is employed before the detector in order to cut off the extra noise due to the rather wide band width of the room temperature amplifiers (6 GHz for MITEQ SMC03 and 20 GHz for SMC05). Small AC-modulation is typically applied on top of the DC-bias so that drift in the noise level is elim-inated by using lock-in techniques after detection. The full noise can then be obtained by numerical integration. This scheme, however, does not eliminate the drift in the gain of the amplifiers. Temperature stabilization of the LNAs, especially the room temperature ones, has been found to decrease this drift substantially. The noise power of a source having an impedance R is given by eV Pnoise = SiR = 4kBT(l -F) + F2eIRcoth — . (2) KBI This formula shows that the thermal noise and the shot noise are intermixed in a manner depending on the Fano-factor, which makes a separation of the contributions of thermal and shot noise complicated. Since the pream-plifier is matched to a transmission line having the im-pedance of Zo = 50 Q, the coupling from the source to the preamplifier is governed by the mismatch between the transmission line and the source. This is governed by reflection coefficient T = (R — ZQ)/{R — Zo) in which R denotes the small-signal resistance of the sample at the operating point. Thus, the noise power Pmeasure coupled to the preamplifier becomes Pmeasure = Pnoise(l ~ \T\2) ~ FSeIZ0j (3) where the latter form is valid in the regime FeV » RBT. Therefore, for samples with only weakly non-linear IV-curves, the Fano factor can be obtained directly as the ratio of the slopes of the noise vs. current curves mea-sured for the tunnel junction and the nanotube samples. Fig. 2 illustrates the resolution achieved on a tunnel junction sample of resistance RT = 7.7 kQ. The signal to noise ratio is clearly so good that the main limitation of our method comes from the requirement of FeV »ksT. As worked out by Spietz et al [12], the cross-over regime between thermal and shot noise can be employed to determine absolute temperature of the sample, and by using the fitted lines we get T = 4.2 K as expected. - 8 - 6 - 4 - 2 0 2 4 6 8 V(mV) FIGURE 2. Noise vs. bias current measured on a tunnel junction with RT = 7.7 kQ. The tunnel junction was made of A1/A10X/A1 using standard two-angle shadow evaporation. ACKNOWLEDGMENTS It is a pleasure to thank T. Lehtinen, L. Korhonen, M. Sillanpaa, and R. Tarkiainen for valuable help. This work was supported by Academy of Finland, and by the Vaisala foundation. REFERENCES 1. P. G. Collins, M. S. Fuhrer, and A. Zettl, Appl. Phys. Lett. 76, 894 (2000). 2. L. Roschier, R. Tarkiainen, M. Ahlskog, M. Paalanen, and P. Hakonen, ,4/?/?/. Phys. Lett. 78, 3295 (2001). 3. M. Ahlskog, R. Tarkiainen, L. Roschier, and P. Hakonen, Appl. Phys. Lett. 11, 4037 (2000). 4. H. W. Ch. Postma, T. F. Teepen, Z. Yao, and C. Dekker, in Electronic Correlations: from meso- to nanophysics, Proc. XXXVIth Rencontres de Moriond, ed. by T. Martin, G. Montambaux, and J. Tran Thanh Van, EPD Sciences, France, 2001, pp. 433-436. 5. P.-E. Roche, M. Kociak, S. Gueron, A. Kasumov, B. Reulet, and H. Bouchiat, Eur. Phys. J. B 28, 217 (2002). 6. H. Ouacha, M. Willander, H. Y. Yu, Y W. Park, M. S. Kabir, S. H. M. Persson, L. B. Kish, and A. Ouacha, Appl. Phys. Lett. 80, 1055 (2002). 7. E. S. Snow, J. P. Novak, M. D. Lay, and F. K. Perkins, Appl. Phys. Lett. 85, 4172 (2004). 8. R. Vajtai, B. Q. Wei, Z. J. Zhang, Y Jung, G. Ramanath, and P. M. Ajayan, Smart Mater. Struct. 11, 691 (2002). 9. R. Tarkiainen, L. Roschier, M. Ahlskog, M. Paalanen, and P. Hakonen, Physica E 28, 57 (2005). 10. L. Roschier and P. Hakonen, Cryogenics, 44,783 (2004). 11. Ya.M. Blanter, M. Biittiker, Phys. Rep. 336, 1 (2000). 12. L. Spietz, K. W. Lehnert, I. Siddiqi, and R. J. Schoelkopf, Science 300, 1929(2003). 1483 

We have constructed a noise measurement setup for high impedance carbon nanotube samples. Our setup, working in the frequency range of 600 – 900 MHz, takes advantage of the fact that the shot noise power is reasonably large for high impedance sources so that relatively large, fixed non‐matching conditions can be tolerated.Peer reviewe

Wu, F.

Roschier, L.

Tsuneta, T.

Paalanen, M.

Wang, T. H.

Hakonen, Pertti J.

Aaltodoc Publication Archive

Aaltodoc

https://aaltodoc.aalto.fi:443/bitstream/123456789/18175/1/A4_wu_f_2006.pdf

Setup for shot noise measurements in carbon nanotubes

Abstract

Similar works

Full text

Available Versions

Crossref

Crossref

Crossref

Aaltodoc Publication Archive

Aaltodoc