Engineering the optical and gas sensing properties of TiO2 via controlled Cu doping

In this study, Cu-doped TiO₂ thin films were successfully fabricated by magnetron sputtering at room temperature, with controlled Cu concentrations achieved through the introduction of Cu strips onto the TiO₂ target. Among them, the TiO₂ sample The structural, optical, electrical, and gas sensing properties of the films were systematically analyzed using multiple characterization techniques. FESEM and AFM analyses revealed significant morphological changes and increased surface roughness with higher Cu doping, leading to the formation of Cu-rich clusters. UV–Vis spectroscopy demonstrated a redshift in the absorption edge and a narrowing of the optical bandgap, accompanied by an increase in Urbach energy, indicating enhanced structural disorder. Hall effect measurements showed a transition from conventional n-type to p-type conductivity. Gas sensing tests revealed that all samples exhibited an unusual increase in resistance upon ethanol exposure, indicating p-type behavior. Among them, the TiO₂ sample with the highest Cu content achieved the greatest sensitivity (5.44) and the fastest recovery time (20.48 s). These results demonstrate that Cu doping effectively modifies the structural and electronic properties of TiO₂, providing a promising approach for the development of high-performance p-type metal oxide gas sensors.