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CNT as Thermal Resistive Sensor

CNT as Thermal Resistive Sensor. April 30, 2010. Yu ZHANG Directed by Prof. Wen J. LI. Measurement Noise. 100dB -. 80dB -. CD Player 2. 90dB -. MEMS Accelerometer 4 (Maximum Value). 70dB -. SNR upper limit of the SMU. 60dB -. MEMS microphone 5 Analog Devices ADMP404. 50dB -.

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CNT as Thermal Resistive Sensor

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  1. CNT as Thermal Resistive Sensor April 30, 2010 Yu ZHANG Directed by Prof. Wen J. LI

  2. Measurement Noise 100dB - 80dB - CD Player2 90dB - MEMS Accelerometer4 (Maximum Value) 70dB - SNR upper limit of the SMU 60dB - MEMS microphone 5 Analog Devices ADMP404 50dB - Cassette Player2 40dB - CCD Camera1 Improving sampling accuracy of the SMU • Weakened signal due to small Resistance • Increased noise due to over-heating 30dB - WIFI: Excellent signal 20dB - 10dB - WIFI: Lowsignal MEMS Accelerometer3 (Maximum Value) WIFI: No signal RFID Reader6 • References • Steven W. Smith, The Scientist and Engineer's Guide to Digital Signal Processing, Chapter 25 • http://en.wikipedia.org/wiki/Audio_system_measurements • J. Silva etc, Systematic characterisation of silicon-embedded accelerometers for mechanomyography, in Journal of Medical and Biological Engineering and Computing, 2006 • T. Kajita etc, A Two-Chip Interface for a MEMS Accelerometer, in IEEE Transactions on Instrumentation and Measurement, Vol. 51, NO. 4, pp853-858, AUGUST 2002 • Analog Devices Datasheet of ADMP404 Omnidirectional Microphone with Bottom Port and Analog Output, 2010 • Z. Fan etc., Signal descriptions and formulations for long range UHF RFID readers, in Progress In Electromagnetics Research, PIER 71, 109–127, 2007

  3. Origin of Research Aconductive thermal flux density to substrate and electrodes thermal flux density to the air caused by convection How to explain the relationship between current and response? 1 CNT is more sensitive to temperature change at low current • References • M. Elwenspoek and R. Wiegerink, Mechanical Microsensors, 2001

  4. Temperature Coefficient of Resistance R0is the sensor’s resistance at T0 R is the sensors resistance at T Testing current = 10uA CNT temperature Ambient temperature

  5. Measurement-induced Joule Heating • Any electrical tests will introduce measuring current to the Device Under Test (DUT) • Nano/Micro structures have very low heat capacitance • Test-induced current will heat up the nano DUT To what level?

  6. Resistance vsCurrent 1nA to 10uA sweep tests at Tamb from 20 ℃ to 80 ℃ with 5 ℃ steps T (℃) ΔR～70kΩ ΔT=?℃ ΔR～10kΩ ΔT=60℃ 420 ℃ • The declination of the R/I curve indicates: • RCNT drops significantly when testing current augments from1nA to 100nA • Higher testing current means higher CNT temperature Unable to determine the temperature increment

  7. Conclusion on TCR Test • The Joule Heating phenomena of the CNT bundle occurs from nA level (or even smaller) • Unable to obtain R0 and T0 unless • The calculated TCR at different testing current cannot be used to judge the thermal resistive properties of CNTs

  8. Proposed Future Work • Explain the Response-Current curve through other approaches • Test and compare the R-I curve of different configurations

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