Synthetic Metals and Semiconductors

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Synthetic Metals and Semiconductors
DAE Developing our collective vision meeting
Sub-committee Physical
Sciences
IGCAR, Kalpakkam April 29, 2004

• G. Amarendra,
• Materials Science Division,
• Indira Gandhi Centre for Atomic Research,
• Kalpakkam 603 102, T.N

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Electrical conductivity
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Polymer backbone - Charge transport
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Band formation- Effect of chemical ligands
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Polymers and the effect of doping on electrical
conductivity
Doped Polyacetylene
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Change - 1010
Emeraldine Effect of protonic acid doping
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Control of Microstructure Anisotropy
Thin films
(3 5 ?m)
(25 30 ?m)
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Various polymers being considered for
conductivity applications
Polyacetylene -(CH)-dopantn
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(No Transcript)
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APPLICATIONS
Conductivity
Electrical activity

• Electrostatic materials
• Conducting adhesives
• Electromagnetic shielding
• Printed circuit boards
• Artificial nerves
• Antistatic clothing
• Piezoceramics
• Active electronics (diodes, transistors)
• Aircraft structures

• Molecular electronics
• Electrical displays
• Chemical, biochemical and thermal sensors
• Drug release systems
• Optical computers
• Ion exchange membranes
• Electromechanical actuators
• Smart structures
• Switches

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Organic Light Emitting Diode
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OPEN/ CHALLENGING PROBLEMS

• Mechanisms for s
• Band picture (?), 1-D metal -
  Anisotropy in conductivity
• Interplay between chemical
  doping/carriers vs. disorder
• Invoking e-- phonon/e- - lattice distortion
• (Correlation length gtgt atomic spacing)
• Simultaneous presence of crystallinity disorder
  
• (Control of microstructure)
• Thermal stability/ Integrity long
  term performance
• Magnetic ordering Para, Ferro, AF
• Phase transitions I M Reversible
  (photoexcitation)
  
  
  
  

I
SC
Metal
Parameters - Doping, control of
disorder (T, P)
s
parameter
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Summary

• Conducting polymers offer the possibility of
  synthesizing semiconductors and metals in a more
  cost-effective and simple means.
• Distinct applications exist in wide areas.
• (Synthesis of metallic polymer comparable
  to Cu)
• Experimental expertise exists for the
  characterization of the chemical doping and
  microstructure (disorder and defects).
• Formation of coherent programme with specialists
  drawn from various research areas can give a
  thrust and fillip to this activity.
• References
• 1 Noble lecture "Synthetic metals A novel
  role for organic polymers"
• A.J. Heeger , Rev. Mod. Phys. 73, 681 (2001)
  Alan G. MacDiarmid, ibid., p. 701H.
  Shirakawa, ibid., p.713.