Journal of Materials Research


Metal-insulator transition in highly disordered carbon fibers

K. Kuriyamaa1 c1 and M.S. Dresselhausa1

a1 Center for Materials Science and Engineering, Departments of Electrical Engineering and Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139


The electronic transition from localized to delocalized states of carriers in a disordered carbon material is investigated by photoconductivity measurements. Phenol-derived activated carbon fibers, where the carriers are strongly localized due to disorder, are heat treated in the range 300–2500 °C to give rise to the insulator-metal transition. Dark conductivity, Raman spectra, and x-ray diffraction patterns are also measured to characterize their structural changes. As a result, the transition temperature was determined to be rather low, around 1000 °C, considering the rapid decrease in the photoconductivity above this temperature. This decrease was ascribed to a fast recombination between the photoexcited carriers and the delocalized carriers generated by heat treatment.

(Received May 13 1991)

(Accepted December 11 1991)


c1 Permanent address: R & D Division, Sumitomo Metal Industries Ltd., Fuso 1-8, Amagasaki, Hyogo, 660 Japan.