Fabrication of high quality and large area graphite thin films by pyrolysis and graphitization of polyimides

Abstract

We have developed large-area, high-quality graphite thin films that are 0.5–3 μm thick. To prepare the graphite films, we used pyrolysis and graphitization of polyimide up to temperatures in the range 2900 °C-3300 °C, which is applicable to industrial-production processing. Given that the graphite layers of the films are highly oriented in the surface plane, they have good physical properties. The resulting electrical conductivity of graphite film of thickness 1.4 μm and area 10 × 10 cm2 that was treated at 3200 °C is 24,800 S/cm, and the electrical conductivity showed metallic temperature dependence. The carrier mobility of the film is 11,700 V/cm2, and the carrier concentrations of electrons (Ne) and holes (Nh) are 6.98 × 1018 cm−3 and 5.90 × 1018 cm−3, respectively. We consider the high electrical conductivity and mobility to have been derived from the homogeneous, highly oriented graphite layers. We found that graphitization of films less than 3 μm thick progresses uniformly throughout the film, and the resulting graphite films have structures with uniform, highly oriented layers. The produced graphite thin films have excellent physical properties and can be easily handled, so we believe that many industrial applications are possible.