A1258150263sCrPM

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Pyroelectric sensors

• What is Pyroelectricity?
• Detectors
• Operation principles
• Fabrication technology
• Competing technology
• Future outlook and summary

Ana López Cabezas André Hallan Tobias Övergaard
IM2654 Smart Electronic Materials
By
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What is Pyroelectricity?
Spontaneous Polarization occurs with heat changes.
?Q p x A x ?T
dT 0 dP 0
dT ? 0 dP ? 0

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But When and Where?
A Tourmaline crystal, one of the first Materials
to be identified with the Pyroelectric property.
Asymmetry affects the coupled effects.
Large heat capacity Small electrical time
constant Easy integration
Ten valid crystal symmetries.
Bulk
Needs polarity, Tc important.
NETD Vn ?T / Vs
Higher performance Small thermal time
constant Interface problems
Thin films
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Applications
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Detectors
Single-element detector
Detector arrays
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Point detectors

• Intruder detection and burglar alarms
• Flame detector and fire detector
• Temperature measurement
• Automatic door switch
• IR spectrometer
• Pollution monitors
• Light control

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Detector arrays

• 1-D linear arrays
• infrared gas detectors arrays capnography
• 2-D arrays
• high quality IR images
• fire fighting
• land mine detection
• process control
• facial recognition
• traffic control

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Operation principle
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Separated with different fields
But if we do not define different fields
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Fabrication technology

• Two main concepts
• Hybride assembly
• Thermal insulation ? cantilever formed using
  micromachining techniques
• Micromachining techniques
• Bulk micromachining ? linear arrays
• Surface micromachining ? 2D arrays

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Example of the fabrication process of a
pyroelectric TFFE (thin film ferroelectric) pixel
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Competing Technologies

• Quantum Detectors
• Concept Applications
• Comparison
• Microbolometers
• Concept Applications
• Comparison

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Quantum Detectors

• Concept
• Photovoltaic
• Cryogenic
• Indium Antimonide, Mercury cadmium telluride

• Applications
• Nightvision systems
• Other military sensors
• IR Astronomy

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Quantum DetectorsComparison

• Needs cryogenic cooling
• Expensive

• Much higher sensitivity
• Getting more mobile

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Microbolometers

• Concept
• 2D-Array
• Variable resistor
• VOX

• Applications
• Uncooled IR Cameras
• Civilian
• Military

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MicrobolometersComparison

• Much easier to produce (MEMS)

• Not as good theoretical sensitivity

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Future outlook Summary

• Single-element detectors
• Work on fabrication issues with 2D-arrays
• Space applications

• Polarization with heat change
• Good sensitivity
• Cheap single-element applications
• Good future potential

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References

• Nanoelectronics and Information Technology
  Rainer Waser
• Pyroelectricity From Ancient Curiosity to Modern
  Imaging Tool Physics Today, August 2005, page
  31
• Picture references
• Slide 5 Physics Today Article
• Slide 6,9 http//www.fuji-piezo.com/prodpyro.htm
• Slide 7,11 Nanoelectronics and Information
  technology
• Slide 8 http//www.glolab.com/pirparts/infrared.
  html
• Slide 12,13 www.flir.com
• Slide 15 www.infraredsolutions.com/html/technolog
  y/microbolometerF.shtml
• Slide 17 http//www.ig.utexas.edu/research/projec
  ts/mars/web_photos/orbiters/athena.jpg