Carbonization and graphitization of Kapton-type polyimide film having boron-bearing functional groups Original Research Article

Kapton-type polyimide film having boron-bearing functional groups in the molecule was synthesized and its carbonization/graphitization behavior was investigated by XPS, SEM, XRD, Raman spectrometry, and the measurements of electronic properties. It was found that >B–N< bonds started to form in the films around 800°C, and these bonds were broken above 1200°C and boron atoms started to substitute carbon atoms in the turbostratic structure. Graphitization was recognized at 2600°C for both boron-doped and undoped films but the boron-doped film had smaller Lc by XRD and more disordered structure which was revealed by Raman spectroscopy. The electronic measurements confirmed that boron could be substituted even in turbostratic structure. The boron-doped film formed at 2600°C showed two-carrier (holes and electrons) type conduction similar to HOPG, but hole carriers were predominant to electrons because of the doping of boron. The boron doping decreases d002 of graphite film but it does not contribute to the development of graphite structure and reduces electric conduction.