A Three Terminal Carbon Nanotube Relay

1
A Three TerminalCarbon Nanotube Relay
Experiment

• S. W. Lee (1,2)
• M. Sveningsson (2)
• Y. W. Park (1)
• E. E. B. Campbell (2)
• J. Kinaret (2)
• M. Jonsson (2)

Theory
1 School of Physics and Nano Systems
Institute-National Core Research Center,
Seoul National University, Seoul 151-747,
Korea 2 Department of Physics, Göteborg
University, SE-41296 Göteborg, Sweden
2
Outline

• Motivation
• Fabrication method of CNT relay structure
• Electromechanical measurements
• (1) Contact mode
• (2) Non contact mode
• Summary and future prospect

3
Motivation

• CNT based Nano electromechanical system (NEMS)

CNT based rotational actuator
Conductance changes according to strain
Nature 424, 408 (2003)
PRL 90, 156401 (2003)
Tunable CNT electromechanical oscillator
CNT tweezers
Science 286, 2148 (1999)
Nature 431, 284 (2004)
4

• CNT based nano relay New NEMS

Kinaret et. al, APL 82, 1287 (2003)
5
Equation of motion
Cantilever deflection
Electrostatic force
Van der Waals force
Short range interaction
Kinaret et. al, APL 82, 1287 (2003) first
theoretical modeling of nano relay
6
Fabrication method ofCNT relay structure
(a)
(e)
(b)
(d)
(c)
10?m
AC
Acid free method to make suspended structure S.
W. Lee et. al Appl. Phys. A 78, 283 (2004)
7
SEM images of CNT relay structures
8
Relation between diameter and suspended length of
CNT
9
Critical point dry after lift off process
Liquid effect due to surface tension of water
After critical point dry process
10
Force-distance measurement of relay structure
10nN of mechanical force is necessary to push
CNT down to the drain electrode
S. W. Lee et al. Nano Lett. 4, 2027 (2004)
11
Estimating electrostatic voltage to make 10nN of
force for dragging CNT
d
x
Approximation parallel plate capacitor
where C0 ?0A/d 10-18 F
Height from the substrate 80 nm
Voltage to make 10nN of dragging force 30V
12
I-Vg characteristics of relay structures (contact
mode)
VSD500mV
contact
S. W. Lee et al. Nano Lett. 4, 2027 (2004)
13
S. W. Lee et al. Nano Lett. 4, 2027 (2004)
14
Theoretical calculation for non contact mode of
relay structure
M. Jonsson, lic. Thesis (2004)
15
I-V characteristics of relay structures
(non-contact mode)
No hysteresis
Studied for shorter structures where contact with
the drain electrode cannot occur
Qualitative agreement with theory
Current modulation with gate voltage
M. Sveningsson, S. W. Lee, E. E. B. Campbell
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Summary Future Prospect

• Controllable arrays of 3-terminal CNT relay
  structures were made using ac dielectrophoresis
  method and E-beam lithography processes.
• The force-distance measurement was done.? The
  mechanical force to pull CNT down to the
  substrate was estimated.
• Electromechanical properties of relay structures
  measured.
• (both contact and non-contact mode were observed
  from transport measurement)
• High frequency measurement to observe resonance
  of relay and switching time is on going

17
Acknowledgements

• This work was supported by the Swedish Foundation
  for Strategic Research (SSF CMOS integrated
  carbon-based nanoelectromechanical systems) and
  EC FP6 funding (contract no. FP6-2004-IST-003673,
  CANEL).
• The Korean co-authors were supported by a STINT
  collaboration project between Göteborg University
  and Seoul National University and the Nano
  Systems Institute - National Core Research Center
  (NSI-NCRC) program of KOSEF and BK21 of MOE, KOREA

18
Critical point dryer (CPD 030, BAL-TEC Co.)

• Processes of critical point dry method
• After lift off with acetone, the sample was
  transferred to an acetone filled critical point
  dryer (CPD 030, BAL-TEC Co.) chamber.
• The chamber was cooled down below 10?C. By
  injecting liquid phase CO2 and discharging the
  media in chamber for several times, CO2 was
  substituted for acetone.
• Then the temperature and pressure of chamber was
  increased simultaneously up to critical point of
  CO2 (T 31?C and P 73bar).
• At this point the phase change from liquid to gas
  was occurred without density change in the
  chamber.
• The drying process was completed when pressure
  was decreased isothermally down to the
  atmospheric.