Energy density-driven structural tuning of Al2O3/AgO films for enhanced toxic gas detection

Abstract

This study examines how laser energy density during pulsed laser deposition (PLD) affects the structural, optical, electrical, and gas-sensing properties of Al₂O₃/AgO thin films. The films were deposited at energy densities of 10.2, 21.2, 31, and 40.8 J cm⁻² and analyzed using XRD, FE-SEM, AFM, UV-vis, and Hall effect techniques. The results showed that increasing the energy density improves the crystallinity and conductivity up to 31 J cm⁻², while excessive energy at 40.8 J cm⁻² induces defects and re-evaporation, enhancing the gas sensitivity due to the increased number of active sites. The optical band gaps ranged from 1.821 to 1.967 eV, varying with the grain size. All films exhibited n-type behavior. Gas sensing tests for NO₂ and H₂S in the range of 40–250 °C revealed the highest sensitivity at 250 °C. The film deposited at 40.8 J cm⁻² showed the best sensing performance due to the oxygen vacancies and nanoclusters. This study confirms that optimizing laser energy enables the tailoring of Al₂O₃/AgO films for enhanced gas sensor applications.