Partial carbonization of aromatic polyimide films

Aromatic polyimide films are partially carbonized between 700 and 1000°C in an atmosphere of hydrogen or nitrogeit electrical conductivity and Hall coefficient have been measured. Electrical conductivity is higher at higher measuring temperatures. The electrical conductivity σ can be expressed as $\text{σ=σ}{}_0\text{exp}\text{(−E/kT)}$, where k is the Boltzman constant; T is the absolute temperature; E depends upon the carbonized temperature. The experimental data show the Hall coefficient R_H is negative, and this implies the majority carriers are negatively charged, i.e. electrons. The specimens are n-type semiconductors. The carrier density η can be expressed by $\text{η=A}{}_1\text{exp}\text{(−E}{}_1\text{/kT)}$ and carrier mobility μ can be expressed by $\text{μ=A}{}_2\text{exp}\text{(E}{}_2\text{/kT)}$. E, E₁ and E₂ depend upon the carbonized temperature.