Photologic

Untersuchung von porösen Nanopartikelstrukturen unter Beleuchtung für die Anwendung als Gassensoren

01/01/2020 to 30/12/2022

The overall goal of this project is a fundamental understanding of the processes occurring in porous sensing structures under illumination. To achieve this goal requires to identify the differences towards temperature-based effects in a conventional heated gas sensor. Therefore, we will investigate the fundamental processes, which are involved in the transduction and reception mechanisms under illumination and the effects of illumination on the surrounding media/gases.
Taking into account the transduction function of a porous nanoparticle layer, the crucial question is how illumination influences the conduction in polycrystalline layers into the core of the particles, through the surface regions and across the particle-particle contacts. The activation of the electronic states within the bandgap resulting from oxygen vacancies and other surface or bulk defects, especially the ones intentionally induced by doping/alloying the material with foreign species, have to be understood in connection with the morphology of the nanoparticle layer.
The surface chemistry under illumination plays an essential role for the reception function. Whereas the influence of elevated temperature on the gas diffusion and oxygen surface ionosorption is already known, it is rather unclear, how illumination influences the reception function. At the same time, it is still ambiguous how the photons interact with the target gas itself. For instance NO2 absorbs light in the wavelength range required to photogenerate free charge carriers over the bandgap of SnO2 or ZnO. Answers to these research questions would improve the understanding of the electrical conduction in granular/polycrystalline layers and the semiconductor surface chemistry in gaseous ambient under illumination.