Characterization of Self-Assembled SnO₂ Nanoparticles for Fabrication of a High Sensitivity and High Selectivity Micro-Gas Sensor

Abstract

In order to refine further the material technology for tin-oxide based gas sensing we are exploring the use of precision nanoparticle deposition for the sensing layer. Layers of SnO₂ nanoparticles were grown on Quartz Crystal Microbalance (QCM) resonators using the layer-by-layer self-assembly technique. Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), and Electron Diffraction Pattern (EDP) analyses were performed on the self-assembled layers of SnO₂ nanoparticles. The results showed that SnO₂ nanoparticle films are deposited uniformly across the substrate. The size of the nanoparticles is estimated to be about 3-5 nm. Electrical characterization was done using standard current-voltage measurement technique, which revealed that SnO₂ nanoparticle films exhibit ohmic behavior. Calcination experiments have also been carried out by baking the substrate (with self-assembled nanoparticles) in air at 350°C. Results show that 50%-70% of the polymer layers (which are deposited as precursor layers and also alternately in-between SnO₂ nanoparticle monolayers) are eliminated during the process.