Investigation on acceptor-donor co-doped SnO a capacitive humidity sensor for respiration detection

Area of Science:

• Materials Science
• Nanotechnology
• Sensor Technology

Background:

• Tin dioxide (SnO2) is a widely studied material for gas sensing applications.
• Oxygen vacancies in SnO2 significantly influence its electrical and sensing properties.
• Developing novel doping strategies can enhance the performance of SnO2-based sensors.

Purpose of the Study:

• To develop a novel capacitive humidity sensor using Al-Si co-doped SnO2.
• To investigate the effect of Al-Si co-doping on the structural, defect, and sensing properties of SnO2.
• To explore the potential of the developed sensor for real-time monitoring of ambient humidity and human respiration.

Main Methods:

• Synthesis of Al-Si co-doped SnO2 materials.
• X-ray Diffraction (XRD) for structural analysis.
• Raman Spectroscopy and Electron Paramagnetic Resonance (EPR) for defect characterization.
• Density Functional Theory (DFT) calculations for electronic structure analysis.
• Fabrication and testing of capacitive humidity sensors.

Main Results:

• Al-Si co-doping resulted in a tetragonal rutile phase SnO2 with decreasing crystallite size.
• Increased oxygen vacancy defects (bridging mode and singly ionized) were observed with Al-Si co-doping.
• DFT calculations confirmed the formation of acceptor-donor complexes.
• The (Al + Si)0.02Sn0.98O2 sensor exhibited high sensitivity (S = 839), low hysteresis (1.94%), and rapid response/recovery times (25 s/5 s).
• The sensor successfully measured respiratory intervals for different breathing states.

Conclusions:

• Al-Si co-doping effectively enhances the humidity sensing performance of SnO2.
• Oxygen vacancy defects play a crucial role in the improved sensing mechanism.
• The developed sensor is promising for real-time humidity and respiration monitoring applications.