Lead-Free Perovskite Thin Films for Gas Sensing through Surface Acoustic Wave Device Detection

Area of Science:

• Materials Science
• Nanotechnology
• Chemical Sensing

Background:

• Thin film technology is crucial for electronic devices like gas sensors.
• Lead-free piezoelectric materials are sought after for environmental and health reasons.

Purpose of the Study:

• To fabricate and characterize surface acoustic wave (SAW) gas sensors using lead-free (1 - x) Ba(Ti0.8Zr0.2)O3-x(Ba0.7Ca0.3)TiO3 (BCTZ50) thin films.
• To investigate the effect of Polyethylenimine (PEI) polymer coating on sensor performance.
• To explore the influence of substrate crystallography on sensor characteristics.

Main Methods:

• Pulsed Laser Deposition (PLD) for BCTZ thin films.
• Matrix Assisted Pulsed Laser Evaporation (MAPLE) for PEI polymer coating.
• Fabrication of SAW devices on SrTiO3 and GdScO3 substrates with varying film thicknesses.
• Gas sensing tests for N2, CO2, and O2.

Main Results:

• Optimized BCTZ thin films were deposited with thicknesses ranging from 50 to 350 nm.
• SAW sensors based on BCTZ/GdScO3 demonstrated enhanced CO2 sensitivity.
• A maximum frequency shift of 39.5 kHz for CO2 was achieved with the PEI-coated BCTZ/GdScO3 sensor, an eightfold improvement.

Conclusions:

• The crystallographic properties of BCTZ films significantly impact SAW device performance.
• PEI polymer coating substantially enhances the gas sensing capabilities of BCTZ-based SAW sensors.
• The developed BCTZ/GdScO3/PEI system shows great potential for highly sensitive CO2 detection.