Enhancing chemiresistor-type NO gas-sensing properties using ethanol-treated lead phthalocyanine thin films

The gas-sensing properties of ethanol-treated lead phthalocyanine (PbPc) thin films, to be used in a chemiresistor-type nitric oxide (NO) gas sensor, are presented. The gas-sensing properties, including current transient, sensitivity, and response time, were studied. It was found in this study that the PbPc thin films post-treated with an ethanol (EtOH) vapor responded faster to NO gas both in adsorption and desorption processes, comparing to those PbPc thin films without any post-treatment. The sensitivity was also enhanced with the post-treatment. A nonlinear diffusion-adsorption model, proposed in the literature for gas-sensing with a semiconductor thin film, has been used to fit our experimental data. The results obtained from the fitting revealed that the EtOH-treated PbPc thin films possess a larger effective diffusion coefficient and a faster response time. For 100-nm PbPc thin films, the power indexes (sensitivity) for both untreated and treated films are 0.38 and 0.65, respectively. Moreover, the model also gives other physical parameters for both untreated and EtOH-treated PbPc films. (c) 2005 Elsevier B.V. All rights reserved.