Optical and structural properties of SnO₂:pd doped with CeO₂ and the possibility of using it in sensors

In the current work, a hydrogen sulfide gas sensor was manufactured from (SnO₂:Pd) and (SnO₂:Pd)_1−x(CeO₂)_x with a range of x = 0.05, 0.1, 0.15, 0.20, and 0.25 wt% using PLD technique employing focused YAG laser with λ of 1064 nm, energy of 400 mJ and number of shots of 200. The thin films were fabricated on the glass substrate and Si wafer with a thickness of 200 ± 05 nm. The impact of CeO₂ content on the structural, surface, and electrical properties, as well as the efficiency of gas sensors, was assessed. Analysis using AFM revealed a transformation of the spherical shape of SnO₂ to a filament-like shape, resulting in a reduction in average particle diameter, while the RMS stiffness increased with the rise in the CeO₂ ratio. The Hall effect measurement indicated that all produced films exhibited n-type conductivity, which then converted to p-type after the CeO₂ content reached 15%wt. Moreover, an increase in the CeO₂ content led to higher carrier concentrations. Gas sensitivity was found to be optimal at 0.1% due to the association with low particle sizes and high-loading carriers. The highest gas sensitivity was observed at operating temperatures of 200 °C, and it increased with gas concentrations as a second-order equation, remaining almost stable at 400 ppm of H₂S gas. Furthermore, the optical properties show an increasing absorption coefficient. On the other hand, the decrease in the optical energy gap is caused by an increase in the width of the tails of the edge of the beams (parity and conductivity) inside the gap.