Bi-layer nanostructures of CuPc and Pd in SAW and resistance hydrogen sensor

Bi-layer nanostructures of copper phthalocyanine (CuPc ∼ 80 nm, ∼100 nm and ∼200 nm) with a very thin film of palladium (Pd ∼18 nm) on the top, have been studied for hydrogen gas-sensing application at ∼30-38 °C, and medium (0,5 – 4%), and low (0,01-0,08%) hydrogen concentrations in synthetic dry air. The structures were obtained by vacuum deposition (first the CuPc and then the Pd film) onto a LiNbO3 (Y- cut Z-propagating) and glass substrates and were tested by means of the Surface Acoustic Wave (in a dual channel delay line configuration) and resistance methods. Very repeatable results have been observed for these three nanostructures with changes in frequency on the level of 100 to 600 Hz, for hydrogen concentration from 0,5 to 4% in air. The absolute response value depends on the CuPc film thickness, the interaction temperature and hydrogen gas concentration and is greater for the bi-layer nanostructure with a medium (100 nm) CuPc film.