DC CONDUCTANCE OF CUPC FILMS PREPARED BY PLASMA ACTIVATED EVAPORATION

A CuPc film with good mechanical and gas sensing properties was prepar ed by the plasma activated evaporation method. The conductivity of the CuPc film approximately satisfies the following equation: sigma = sig ma (o) exp(-E/kT) where E is the activation energy. The activation ene rgies of the films deposited at high pressures (200 and 300mtorr) are 0.7 similar to 0.8eV which are almost the same with Eg/2 of the sublim ated CuPc film. For the films deposited at low pressures (20 and 100mt orr), the activation energies are 0.1 similar to 0.4 eV depending on t he gas environment. As the deposition pressure of the CuPc film decrea ses, the porosity of the film increases and thus the surface area wher e NOx gas molecules can be adsorbed increases. This results in the inc reases of the DC conductivity and the NOx gas sensing sensitivity with decreasing CuPc deposition pressure.