Plasma-deposited copper phthalocyanine: A single gas-sensing material with multiple responses

Copper phthalocyanine (CuPc) thin films have been deposited by glow discharge-induced sublimation (GDS). This physical technique allows to produce very high porosity films, whose response to gases is much more intense than evaporated films. It has been found that both electrical and optical properties of these films change upon gas exposure due to the gas/film interaction. Electrical response of the films has been tested by exposing the samples to NOx-containing atmospheres and by measuring the slope of the electrical surface current versus gas concentration. This way NO2 and NO concentrations down to 0.1 ppm and 10 ppm have been measured, respectively, with response times shorter than 2 min. Optical responses have been tested by measuring the change of light reflectance at a fixed wavelength upon exposure to ethanol-containing atmospheres down to concentrations of few thousands of ppm. Response times of less than 10 s have been obtained.