Abstract
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 1.10×10
22 to 7.15×10
22
m
−3 for devices tested in situ and after exposure to dry air for 120 h, respectively.