PREPARATION AND FABRICATION OF A GAS SENSORCR₂O₃ IMPREGNATED WITH RARE EARTH ELEMENTS (AU) AND PRECIPITATED BY CHEMICAL BATH TECHNIQUE

Abstract

Thin films were prepared from Cr₂O₃ doped with gold (2–8%) using the chemical bath technique, and their structural, optical, electrical, and photosensitive properties were studied. XRD results showed that the primary phase was rhombohedral Cr₂O₃, with Au peaks appearing at higher percentages. The crystallite size gradually decreased with doping due to the increased growth centers. SEM images showed that the grain size decreased from ~85 nm at 2% to ~53 nm at 8%, with a rougher surface rich in active sites. Optically, the absorbance increased and the transmittance decreased with increasing Au percentage, with the energy gap narrowing from ~3.05 eV to ~2.72 eV due to plasmonic resonance and electronic structure modification. Electrically, Hall measurements confirmed that all films were p-type, and that the carrier concentration and mobility increased with doping, resulting in improved conductivity and reduced resistivity. In gas sensing tests (H₂S), the response time was shorter than the return time, and both decreased with increasing temperature. However, the sensitivity gradually increased to ~75% at 8% Au, 300°C. These results indicate that doping Cr₂O₃ with gold led to integrated improvements in the structural, optical, and electrical properties, which directly enhanced the sensitivity performance, making these films promising candidates for gas sensing applications.