Low frequency capacitance characterization of α-phase nickel phthalocyanine/lead interfaces: Effects of temperature and oxygen doping

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 7.15×1022m-3 for devices tested in situ and after exposure to dry air for 120 h, respectively. © 2004 Elsevier Ltd. All rights reserved.