Graphitization behavior of Kapton-derived carbon film related to structure, microtexture and transport properties Original Research Article

Graphitization behavior of the carbonized film of commercially available aromatic polyimide film Kapton 25 μm in thickness was studied by X-ray diffractometry, measurements of the transport properties such as the electrical resistivity, Hall coefficient and magnetoresistance, and scanning electron microscopy. The specimens were films carbonized at 900 °C and heat-treated at temperatures between 1000 and 3000 °C with a step of 100 °C. For the specimens carbonized and heat-treated below 2000 °C, the average lattice constant a0 was measured to be lower than that of the single crystal of graphite. Changes related to the transformation from the turbostratic structure to the graphitic occurred at a heat treatment temperature around 2200 °C in the microtexture on the fracture surface and the resistivity at liquid nitrogen temperature. The changes also appeared in the ratio of the resistivity at room temperature to that at liquid nitrogen temperature, and the Hall coefficient and magnetoresistance at liquid nitrogen temperature. The dependences of the resistivity ratio and also the Hall coefficient on HTT for the specimens with turbostratic structure can be related to the average crystallite size L0(110) along the a-axis. The results of the resistivity, Hall coefficient and magnetoresistance were analyzed by a simple model.