The influence of chlorine on the electrical properties of lead phthalocyanine thin film gas sensors

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Abstract
Quantitative studies of changes in semiconductor behaviour of PbPc thin films as a function of exposure to chlorine, annealing in chlorine, and subsequently in vacuum, were made for a range of temperatures. It was found that Cl2 generates acceptor levels within the band gap of the PbPc. The acceptor level energy is a function of the concentration of chlorine incorporated into the bulk of the PbPc. The current-voltage characteristics at fixed temperatures and the variation of current as a function of temperature at constant bias voltage have been established. Both ohmic and space charge-limited conduction (SCLC) were identified and found to be controlled by the concentration of chlorine incorporated within the PbPc bulk. Optimized measuring conditions for the use of PbPc films as a viable chlorine sensor are also reported.