Surface Acoustic Wave Hydrogen Sensors Based on Nanostructured Pd/WO₃ Bilayers

Area of Science:

• Materials Science
• Chemical Engineering
• Sensor Technology

Background:

• Surface Acoustic Wave (SAW) sensors are crucial for gas detection.
• Tungsten oxide (WO₃) and palladium (Pd) are key materials for hydrogen sensing.
• Controlling nanostructure is vital for optimizing sensor performance.

Purpose of the Study:

• To investigate the impact of nanostructure in Pulsed Laser Deposition (PLD)-deposited Pd/WO₃ films on room temperature (RT) hydrogen sensing.
• To correlate film morphology and crystalline structure with SAW sensor performance.
• To achieve enhanced hydrogen detection sensitivity at RT.

Main Methods:

• Fabrication of WO₃ thin films using PLD with varied substrate temperatures and oxygen pressures.
• Characterization of WO₃ nanostructure and crystalline properties using X-ray Diffraction (XRD).
• Deposition of nanoporous Pd layers onto WO₃ films to create Pd/WO₃ bilayers.
• Testing of SAW sensor response to hydrogen at room temperature.

Main Results:

• Nanoporous WO₃ films were achieved at high deposition pressures.
• High substrate temperatures at lower pressures resulted in c-axis nanocolumnar WO₃ growth.
• Predominantly c-axis WO₃ growth significantly influenced sensing properties.
• Nanoporous Pd/WO₃ bilayers demonstrated good RT hydrogen sensing, achieving sensitivities of 0.12–0.13 Hz/ppm.
• Nanocolumnar WO₃ structures yielded sensitivities of 0.1 Hz/ppm.

Conclusions:

• The nanostructure of PLD-deposited Pd/WO₃ films critically affects RT hydrogen sensing performance in SAW sensors.
• Nanoporous WO₃ films, especially when combined with nanoporous Pd layers, offer superior hydrogen detection capabilities.
• The developed SAW sensors with optimized Pd/WO₃ nanostructures show competitive performance compared to other WO₃-based detectors.