CO2 sensing performance enhanced by Pt-catalyzed SnO2/porous-silicon hybrid structures

Abstract

In this work, pristine and Pt-catalyzed SnO2 hybrid structures were designed over porous Si (p-Si) substrates via chemical bath deposition. CO2 gas sensing properties such as sensing response, response/ recovery time were studied as a function of different platinum concentrations and compared with the devices prepared over c-Si substrates. TEM analysis confirms the nanometric size of ∼2.5 ​nm of the Pt nanoparticles. XRD analysis for the hybrid nanostructures confirms the presence of tetragonal structure of SnO2. SEM and EDS analysis of the SnO2 nanostructures confirms the spherical morphology and the composition respectively. Significant sensing response of hybrid nanostructures could be obtained at low operating temperature (∼100 ​°C). At an optimal concentration of PtNPs, the sensitivity of pSi based hybrid structures increased by a factor of ∼7.5 compared to the ones on crystalline-Si. The higher sensitivity is possibly due to the charge carrier exchange enhancement in the Pt–SnO2 interface in addition to the high surface area provided by p-Si. The increment in the p-Si surface area also led to the higher population of active sites and the charge transfer leads to a more efficient dissociation of adsorbed H2O molecules, which further served as active sites for CO2 detection. The CO2 gas sensing mechanism with respect to different substrate and Pt addition is explained in terms of adsorbed OH− ions reacting with CO2 molecules at the SnO2 surface. The utilization of the proposed hybrid structures with high surface area favors the miniaturization of possible device fabrication for real-life applications.

Keywords

• CO2 sensing enhancement
• SnO2 thin films
• Porous silicon
• Pt nanoparticles