Low temperature NO₂ gas sensing with ZnO nanostructured by laser interference lithography

Area of Science:

• Materials Science
• Chemical Engineering
• Sensor Technology

Background:

• Conductometric gas sensors based on zinc oxide (ZnO) are recognized for their sensitivity, cost-effectiveness, stability, and ease of fabrication.
• Nitrogen dioxide (NO2) is a toxic and irritating gas, necessitating the development of effective detection methods.

Purpose of the Study:

• To investigate the effect of nanostructuring ZnO thin films on their NO2 sensing performance.
• To develop a highly sensitive and stable conductometric sensor for NO2 detection, particularly at lower temperatures.

Main Methods:

• ZnO thin films were grown using aerosol-assisted chemical vapor deposition.
• Nanostructuring was achieved via laser interference lithography with a UV laser, creating a 2D periodic pattern with an 800 nm period.
• Sensor performance was evaluated by measuring resistance changes in response to NO2 at various temperatures and humidity levels.

Main Results:

• Nanostructuring resulted in vertically oriented ZnO grains and a 2D periodic nanopattern.
• The nanostructured sensors exhibited significantly enhanced NO2 sensitivity, especially at temperatures below 125 °C, including room temperature operation.
• Compared to non-nanostructured films, nanostructured ZnO showed a 600% resistance change for 4 ppm NO2 at 175 °C (vs. 400%), and importantly, enabled NO2 sensing at room temperature.
• Improved stability and gas sensing performance under humid conditions were observed for nanostructured sensors.

Conclusions:

• Laser-induced nanostructuring of ZnO films effectively enhances NO2 sensing capabilities.
• The developed nanostructured ZnO sensors offer promising room-temperature detection of NO2 with improved sensitivity and stability, suitable for practical applications.
• The enhanced performance is attributed to increased surface defects and surface-to-volume ratio in the nanostructured material.