Photoconductivity has been observed in vapor grown graphite fibers with a high quantum efficiency of carriers generated by photons. The photocurrent varies approximately as the square root of the intensity of illumination. No change in the growth or decay time of the photocurrent is observed as a function of illumination intensity or of the temperature. The photocurrent observed in semi-metallic graphite fibers is attributed to transitions between localized defect states which act as traps for photo-exited carriers. As the heat treatment temperature is raised above 1500 Kelvin, vapor grown graphite fibers show a decrease in the photocurrent due to the annealing of defects and an increase in the electron-hole recombination time. Keywords Photoconductivity, graphite fibers, Effect of heat treatment temperature.
Rept. for 1 Sep 86-31 Aug 87,
Prepared in cooperation with Bell Communications Research, Murray Hill, NJ.