Nanowire thermocouple

Nanowire

Thermocouple

Characterization platform

GOKUL G NAIR

REG NO: 10429023

Overview

• Introduction

• Characterization platform layout

• Fabrication and Measurement

• Summary and Conclusion

• References

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Introduction

If I want something small,I need some measuring thing small…

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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.4

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

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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Drawback

Nanometer scaled dimensions exhibit altered

Seebeck coefficients

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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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• Characterization platform featuring differential temperature measurement setup

• A spatially confined heat source - raise the temperature of hot junctions only

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

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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• 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%

Calibration

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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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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 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.


• 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

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

Thank you !

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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…

Engineering

Nanowire thermocouple