Work

Optimizing ozone sensing performance of Co-doped ZnO thin films via defect engineering

Year: 2026

Type: article

Abstract: Semiconducting metal oxides (SMOs) have been extensively employed as sensing materials for the detection of various toxic gases. Among them, zinc oxide (ZnO) is a multifunctional n-type semiconductor that exhibits potential properties for gas-sensing, particularly toward oxidizing gases. In this study, cobalt-doped ZnO thin films were synthesized via spray pyrolysis and investigated for their application as resistive ozone sensors. All thin films exhibited a hexagonal wurtzite structure with no detectable secondary phases. Furthermore, incorporation of Co 2 + ions into the ZnO lattice was confirmed. Photoluminescence measurements revealed a broad blue emission band associated with shallow-donor defects, which was found to correlate directly with an increased density of active sites on the film surface. Electrical measurements showed that the thin film containing 2.5 mol% Co exhibited a 37-fold enhancement in O₃ sensor response at ppb levels compared to pristine ZnO, attributed to shallow-donor -defect-mediated adsorption mechanisms. Furthermore, thermal annealing under reducing and oxidizing atmospheres was deliberately used as an independent defect-modulation strategy, confirming that the enhancement in O₃ sensor response is governed by blue-luminescence-related defects. These findings suggest blue luminescence as a potential optical parameter for optimizing ZnO-based ozone sensors, offering a rapid and non-destructive approach for sensor design.

Source: Materials Research Bulletin

DOI: 10.1016/j.materresbull.2026.114174