1918 K
36 pp.
 
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TitlePhotoconductivity of Activated Carbon Fibers
Author(s)Kuriyama, K.; Dresselhaus, M. S.
Publication DateAugust 1990
Report NumberUCRL-CR-104934
Unique IdentifierACC0419
Other NumbersLegacy ID: DE91000814; OSTI ID: 6824682
Research OrgLawrence Livermore National Laboratory (LLNL), CA (USA)
Contract NoW-7405-ENG-48
Sponsoring OrgU.S. Department of Energy, Assistant Secretary for Defense Programs (DOE/DP)
Subject36 Materials Science; Activated Carbon; Photoconductivity; Carbon Fibers; Electrical Properties; Phenols; Temperature Dependence; Adsorbents; Aromatics; Carbon; Electric Conductivity; Elements; Fibers; Hydroxy Compounds; Nonmetals; Organic Compounds; Physical Properties
Related Web PagesMildred [Millie] Dresselhaus and her Impacts on Science and Women in Science
AbstractThe photoconductivity is measured on a high-surface-area disordered carbon material, namely activated carbon fibers, to investigate their electronic properties. Measurements of decay time, recombination kinetics and temperature dependence of the photoconductivity generally reflect the electronic properties of a material. The material studied in this paper is a highly disordered carbon derived from a phenolic precursor, having a huge specific surface area of 1000--2000m{sup 2}/g. Our preliminary thermopower measurements suggest that this carbon material is a p-type semiconductor with an amorphous-like microstructure. The intrinsic electrical conductivity, on the order of 20S/cm at room temperature, increases with increasing temperature in the range 30--290K. In contrast with the intrinsic conductivity, the photoconductivity in vacuum decreases with increasing temperature. The recombination kinetics changes from a monomolecular process at room temperature to a biomolecular process at low temperatures. The observed decay time of the photoconductivity is {approx equal}0.3sec. The magnitude of the photoconductive signal was reduced by a factor of ten when the sample was exposed to air. The intrinsic carrier density and the activation energy for conduction are estimated to be {approx equal}10{sup 21}/cm{sup 3} and {approx equal}20meV, respectively. The majority of the induced photocarriers and of the intrinsic carriers are trapped, resulting in the long decay time of the photoconductivity and the positive temperature dependence of the conductivity.
1918 K
36 pp.
 
View Document 
  


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