Chemi-resistive behavior of spray deposited Cu-doped TiO₂ thin films: application in hydrogen sensing devices

Hydrogen has received a lot of attention and is regarded as the most promising energy source of the twenty-first century because of its high energy density and eco-friendliness. However, there are increasing concerns about its safe use, storage, and transportation. The present research study scrutinizes the chemi-resistive behavior of pure and Cu-doped TiO₂ thin films that may be applied to the creation of hydrogen sensing devices. The spray technique was used to synthesize the samples with different levels of Cu content (0, 0.2 and 0.4 wt %) on thermally oxidized Si substrates. The samples were characterized by grazing incidence X-ray diffraction (GIXRD), atomic force microscopy (AFM), field emission scanning electron microscopy (FESEM), and energy dispersive X-ray (EDX) analysis. The hydrogen chemi-resistive behavior of the samples was assessed and the sensing mechanism of the pure and doped samples was analyzed. The results showed that Cu-doping significantly affected the hydrogen sensing performance of the TiO₂ thin films due to the increase of oxygen adsorption sites. The sample of 0.4 wt % Cu-doped TiO₂ (the most sensitive sample) showed a response value of 2600% with a reaction time of 55 s to 1000 ppm of hydrogen at the operating temperature of 200 °C. It was also selective to H₂ compared to CO₂, NO₂, NH₃, and LPG. The evaluation of the reliability of the mentioned sample revealed that it can be considered as a potential for hydrogen sensing devices.