Complex impedance measurements of capacitor structures on silicon with copper phthalocyanine dielectric

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Abstract
Measurements were made of the capacitance and the conductance of several capacitor structures with a copper phthalocyanine (CuPc) dielectric at different voltages and in the frequency range of 102–106 Hz. A thermally evaporated CuPc film about 1300 Å thick was fabricated in a parallel-plate capacitor between gold and aluminum electrodes (Al‖CuPc‖Au). Two distributions of relaxation times are observed in this frequency range. At low frequencies voltage-dependent polarization (possibly interfacial polarization) appears to be the dominant mechanism of current conduction. At high frequencies a relatively voltage-independent hopping within and/or between molecules appears to be dominant. The CuPc remains polarized for a long time. Measurements were also made of the capacitance-voltage (C-V) characteristic of a Al‖CuPc‖SiO2‖Si capacitor at 104, 105, and 106 Hz for different scanning rates. The basic features of the device’s C-V characteristics are discussed.