Photoconductivity: A probe of defect states in carbon aerogels

Journal Article · Wed Jun 01 04:00:00 EDT 1994 · Physical Review, B: Condensed Matter; (United States)

DOI:https://doi.org/10.1103/PhysRevB.49.15027· OSTI ID:7207433

Reynolds, G A.M.; Wang, Z H; Dresselhaus, M S ^[1]; Fung, A W.P. ^[2]; Pekala, R W ^[3]

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1. Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)
2. Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)
3. Department of Chemistry and Materials Science, Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)

The photoconductivity and dark conductivity of carbon aerogels with various heat-treatment temperatures, [ital T][sub HT], and densities are studied. Unlike the trend for as-prepared samples, the magnitude of the photoconductivity for heat-treated ([ital T][sub HT][gt]1050 [degree]C) carbon aerogel samples decreaes as the sample density and heat-treatment temperature increase. We propose a model which quantitatively explains the observed temperature dependence of the photoconductivity data. Based on this model, we attribute the observed photoconductivity to photoholes present in the system. The number of defect states and their corresponding energy decrease with increasing [ital T][sub HT] and increasing density. The decrease in the energy is attributed to a decrease in the screening effect of the defects on trapped charges. The effect of increasing the heat-treatment temperature causes the structure of the carbon aerogel to become more graphitic, especially for aerogel samples with higher mass density.

• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 7207433
• Journal Information: Physical Review, B: Condensed Matter; (United States), Journal Name: Physical Review, B: Condensed Matter; (United States) Vol. 49:21; ISSN PRBMDO; ISSN 0163-1829
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360606* -- Other Materials-- Physical Properties-- (1992-)
CARBON
COLLOIDS
DISPERSIONS
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
ELEMENTS
GELS
HEAT TREATMENTS
NONMETALS
PHOTOCONDUCTIVITY
PHYSICAL PROPERTIES
TEMPERATURE DEPENDENCE
TEMPERATURE RANGE
TEMPERATURE RANGE 0000-0013 K
TEMPERATURE RANGE 0013-0065 K
TEMPERATURE RANGE 0065-0273 K