研究目的
To fabricate nanostructured ZnO thin films using the SILAR method and investigate their structural, optical, and chemical properties for application as an ammonia vapour sensor, with a focus on achieving high sensitivity and low detection limits.
研究成果
The nanostructured ZnO thin films fabricated by SILAR method exhibit excellent structural, optical, and chemical properties, with the 50-cycle film showing the best crystallinity and sensing performance. It demonstrates high sensitivity (215% for 50 ppm ammonia), fast response and recovery times, and a low detection limit of 1 ppm at 200°C. The film is stable and reproducible, making it a promising candidate for ammonia sensing applications in environmental monitoring and medical fields. Future work could focus on enhancing selectivity and operating at lower temperatures.
研究不足
The study is limited to ZnO thin films fabricated by SILAR method on glass substrates; other substrates or methods were not explored. The sensor operates optimally at 200°C, which may not be suitable for room-temperature applications. Selectivity to ammonia over other gases is a challenge, and long-term stability beyond 60 days was not tested. The detection limit of 1 ppm is low but could be improved with further optimization.
1：Experimental Design and Method Selection:
ZnO thin films were deposited on glass substrates using the SILAR method, which involves alternate dipping in cationic (alkaline zinc sulfate) and anionic (hot deionized water) solutions for various cycles (10, 30, 50). This method was chosen for its simplicity and cost-effectiveness.
2：0). This method was chosen for its simplicity and cost-effectiveness. Sample Selection and Data Sources:
2. Sample Selection and Data Sources: Glass substrates were cleaned and used for deposition. Samples were prepared with different deposition cycles to study the effect on film properties.
3：List of Experimental Equipment and Materials:
Equipment includes Holland Philips Xpert diffractometer for XRD, Holland Philips XL30 microscope for SEM and EDX, AFM in contact mode, PerkinElmer Lambda 25 UV-vis spectrophotometer, VG multilab 2000 XPS equipment, Perkin Elmer Spectrum 100 FTIR spectrometer, and a home-built gas sensing chamber with LabVIEW software and DAQs for resistance measurement. Materials include zinc sulfate, sodium hydroxide, deionized water, and glass substrates.
4：Experimental Procedures and Operational Workflow:
Substrates were cleaned, then dipped in cationic solution for 3s, followed by anionic solution for 3s, repeated for specified cycles. Films were characterized using XRD, SEM, AFM, UV-vis, XPS, FTIR, and gas sensing tests at various temperatures and ammonia concentrations.
5：Data Analysis Methods:
Crystallite size was calculated using Debye Scherer formula, microstrain and dislocation density were derived from XRD data, optical band gap was estimated using Tauc plot, sensitivity was calculated using S% = (R0 - Rg)/Rg * 100, and response/recovery times were measured from resistance transients.
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