Superior functionality by design: selective ozone sensing realized by rationally constructed high-index ZnO surfaces

Area of Science:

• Materials Science
• Nanotechnology
• Surface Chemistry

Background:

• Zinc oxide (ZnO) nanowires are crucial for gas sensing applications.
• Controlling surface morphology and crystallographic orientation is key to enhancing sensor performance.
• Nonpolar surfaces of ZnO nanowires often exhibit limited gas sensing capabilities.

Purpose of the Study:

• To develop a method for transforming smooth, nonpolar ZnO nanowire surfaces into high-index polar surfaces.
• To investigate the effect of surface morphology and crystallographic planes on ozone sensing.
• To compare the ozone sensing performance of different ZnO nanowire structures.

Main Methods:

• Fabrication of c-axis-oriented ZnO nanowires with smooth, nonpolar surfaces via vapor deposition.
• Coating of ZnO nanowires with polycrystalline ZnO thin films using atomic layer deposition (ALD).
• Annealing of ZnO-ZnO core-shell nanostructures at 800 °C to induce surface transformation to zigzagged, high-index polar surfaces.

Main Results:

• The annealing process successfully transformed smooth ZnO nanowires into zigzagged nanostructures with high-index polar surfaces.
• Zigzagged ZnO nanowires exhibited significantly higher sensitivity to ozone (O3) compared to smooth and core-shell nanowires.
• The enhanced sensitivity of zigzagged nanowires is attributed to their defect-rich, high-index polar surfaces.

Conclusions:

• Surface engineering of ZnO nanowires by transforming nonpolar to polar surfaces is an effective strategy for improving gas sensing.
• High-index polar surfaces, rich in defects, play a critical role in enhancing the sensitivity of ZnO-based gas sensors.
• The developed technique offers a pathway for fabricating advanced ZnO nanostructures for high-performance gas sensing applications.