Nanowire Thermocouple- Characterization platform

1. Nanowire
Thermocouple
Characterization platform
GOKUL G NAIR
REG NO: 10429023

2. Overview
• Introduction
• Characterization platform layout
• Fabrication and Measurement
• Summary and Conclusion
• References
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3. Introduction
If I want something small,
I need some measuring thing small…
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4. Nanowires
• Solid, rod-like materials with diameters
in the 5-100 nm range
• Made from metals or semiconducting
metal oxides.
• Mainly used as sensors
• Silicon nanowires for Electrical
applications.
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5. Thermocouple
• Electrical transducer – Convert Thermal Energy into Electrical Energy
• Two Wires - Different materials
• Different Seebeck coefficients
• Hot & Cold junctions
• Voc = [SA − SB ]ΔT
• Temperature upto 1400˚C
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Temperature emf curve for thermocouple

7. Nanowire Thermocouple
• Used as thermal sensors
• High spatial resolution for few nanometers
• Fast response time
• Wide range of applications
 Temperature monitoring in IC fabrication
 Used as thermal sensors in Nuclear & thermal power generators
 etc
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8. Drawback
Nanometer scaled dimensions exhibit altered
Seebeck coefficients
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9. Calibrate the Nanowire thermocouple
• To accurately characterize their relative Seebeck coefficients (SA−SB )
• Precise knowledge of the temperature difference between the hot and cold
junctions of the thermocouple
• Precise knowledge of the generated open-circuit voltage
• Commonly temperature difference is made - cold junction is placed in an ice bath
while its hot junction is heated
• Nanowire thermocouple, a hot or cold bath would uniformly change the
temperature of the entire structure.
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10. • Characterization platform featuring differential temperature measurement setup
• A spatially confined heat source - raise the temperature of hot junctions only
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resistive
• Thermometers located near the hot and cold junctions of the thermocouple
• For demonstrate the operation of this characterization platform
A palladium-gold nanowire thermocouple
75 × 40 nm² cross section

11. Characterization platform layout
• Consists
 of a palladium-gold nanowire thermocouple
 a resistive palladium heater
 two resistive palladium thermometers
 located on a SiO2 layer on a Si substrate
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Calibration
• A straight (6 μm long) wire
• Temperature measured by resistive thermometer -
average temperature between its inner most terminals
• Resistive thermometer and the hot junction of the
thermocouple equidistant on either side of the heater
• Cold junction of the thermocouple is separated from
the heater by approximately 50 μm
• Response to 300 μA of current through the heater
• Error is 14.2%

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Modified design platform
• For reducing error
 Both thermocouple &
thermometer have Four
terminals
• Error reduced to 2%
• Error is independent of the
current in the heater, between 50
and 300 μA.

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15. Fabrication And Measurements
• Fabricated on top of 640-nm-thick thermally grown SiO2 on a silicon wafer
• Measuring of temperature and open-circuit voltages, are patterned by optical
lithography
• Finer structures of the characterization platform are patterned by electron-beam
lithography.
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Fabrication
• Heater, thermometers, and First half
of the thermocouple are metallized
with 40-nm thick palladium
• Remaining half of the thermocouple
metallized with 40 nm of gold
• Widths of the wires of the heater,
thermometers, and thermocouple are
75nm each
• Scanning Electro microscope shows
the entire device

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Determining the relative Seebeck coefficient of
Pd-Au nanowire thermocouple
• Voc = [SA − SB ]ΔT
• Voc for known temperature difference between the hot and
cold junctions
• Resistive thermometers and the heater have to be calibrated

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Calibration of resistive palladium thermometers
• A reference IC temperature transducer (AD590)
• Heated by heated air ambience.
• Temperatures from 240 to 310 K of each of the four-terminal thermometers
is measured using a resistance bridge
• A temperature coefficient of resistance ,∝ is find out
• ∝ for the resistive palladium thermometers was measured: ∝(294 K) =
0.199%/K
• The temperature of the thermometers can be calculated from their measured
resistance

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Calibration of heater
• Small ac current i with frequency in the
range of f = 20–200 Hz is passed
• Power dissipated in the heater is
proportional to i²
• Resistance of the thermometers was
measured with a four-terminal resistance
bridge for various magnitudes of currents
• Corresponding temperatures of the hot and
cold junctions of the thermocouple is
calculated.

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Seebeck coefficient of the palladium-gold
nanowire thermocouple
• Voc & ΔT find out at around 3–300
μA of current passing through the
heater
• open-circuit voltage across the
thermocouple was measured at 2f
using a low noise differential amplifier
• Seebeck coefficient is calculated.
• Voc = [SA − SB ]ΔT
• the relative Seebeck coefficient:
SPd-Au(294 K) = 2.963 ± 0.004 μV/K.

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Advantages
• Small in size
• 84% more efficient than a bulk-sized normal thermocouple
• Can used in both large and nano scaled equipment's
• High spatial resolution
• Very high response time due to their small size and thermal volume
• Errors will be less than 2%
• etc.

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Applications
• Temperature monitoring in IC
fabrication
• Thermal sensors in Nuclear &
Thermal power generators
• Thermal sensors in space
utility vehicles
• Bio- Sensors
• Etc

23. Summery and Conclusion
• Small in size - High spatial resolution - High response time
• Physical properties such as the Seebeck coefficient alters due to nano size
• An improved characterization platform.
• Palladium – gold nanowire
• A resistive heater, a nanowire thermocouple, and resistive thermometers
• Characterization platform was designed to ensure an accurate temperature
measurement.
• 84% more efficient 23

24. Thank you !

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25. Reference
• Nanowire Thermocouple Characterization Platform Gergo P. Szakmany, Peter M. Krenz,
Member, IEEE, Louisa C. Schneider, Alexei O. Orlov, Gary H. Bernstein, Fellow, IEEE, and
Wolfgang Porod, Fellow, IEEE EE TRANSACTIONS ON NANOTECHNOLOGY, VOL. 12,
NO. 3, MAY 2013
• http://en.wikipedia.org/wiki/nanowire
• http://en.wikipedia.org/wiki/Thermocouple
• http://en.wikipedia.org/wiki/Seebeck_effect#Seebeck_effect
• http://en.wikipedia.org/wiki/Lithography
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I’ll be happy to answer your
Questions…