Resistivity, Hall coefficient, magnetoresistance, and microtexture of cellulose carbon films

Dense carbon films of about 20 μm in thickness were prepared from a commercially available cellulose film of 40 μm thick by heat treatment up to 900°C. Carbon films thus obtained were heat treated at temperatures between 1800 and 3000°C for 30–60 min. The heat-treated carbon films were investigated by the measurements of resistivity, Hall coefficient and magnetoresistance at liquid nitrogen temperature. Reflected and transmitted X-ray diffraction experiments and observations by a high-resolution scanning electron microscope (SEM) were also carried out. The results of the resistivity and Hall coefficient for high-temperature-treated specimens indicated that the carbonized film was more graphitizable than bulk glass-like carbons. The magnetoresistance and X-ray diffraction profiles for the high-temperature-treated specimens suggested that each of these specimens substantially consisted of the matrix of granular microtexture and the graphite layer skin. The skin was clearly observed by SEM for the specimens heat-treated at 2800 and 3000°C and their thickness was 100–300 nm.