Low frequency capacitance characterization of α-phase nickel phthalocyanine/lead interfaces: effects of temperature and oxygen doping Original Research Article

The Schottky barrier characteristics of evaporated α-phase nickel phthalocyanine/lead (α-NiPc/Pb) structures were investigated using the small AC signal capacitance–voltage (C–V) technique. It was established that for junctions fabricated and tested in situ at room temperature detection of the barrier depletion layer is not possible. Voltage-dependent capacitance characteristics are detected only upon heating or after exposure of the devices to dry air for prolonged periods of time. The C–V response is attributed to the increase of carrier concentration, first due to increased temperature and second due to p-type doping induced by oxygen absorption within the α-NiPc layer. The acceptor state density was determined to be in the range 1.10×1022 to 7.15×1022 m−3 for devices tested in situ and after exposure to dry air for 120 h, respectively.