ELECTRONIC-PROPERTIES OF NITROGEN-DOPED GRAPHITE FLAKES

Thermolyses of several nitrogen-containing heteroaromatic compounds were carried out at 800-degrees-C, utilizing the identical experimental conditions under which benzene forms graphite flakes, to yield nitrogen-doped graphitic flakes (NDGs) having similar disordered structures. Heat treatment of the NDGs in the range 1000-1600-degrees-C results in an increase of the graphitic order with some retention of significant nitrogen content (between 0.5 and 6.4%). These NDGs show low-temperature electronic behavior strikingly different from the benzene-derived carbons: (a) a strong decrease in low-temperature resistivity (rho) with decreasing temperature and (b) negative magnetoresistance at low magnetic fields applied parallel to the c axis. In these ways NDGs resemble doped semiconductors in their electronic properties, whereas the pure benzene-derived carbons can best be treated in terms of a variable-range hopping mechanism.