One-Step Fabrication of Nanocrystalline Nanonetwork SnO₂ Gas Sensors by Integrated Multilaser Processing

An integrated multilaser process is developed to fabricate nanocrystalline nanonetwork SnO₂ gas sensors in one integrated procedure, which combines electrodes fabrication, nanomaterials deposition, and postannealing. Interdigit electrodes are fabricated on an Au-coated fused silica substrate using a picosecond (ps) laser, which ablates the Au coating from the back of the substrate to pattern the electrodes. A novel transmitted Ps laser deposition (TPLD) process is designed to deposit SnO₂ nanonetwork on the interdigit electrodes with precise deposition area control under a close target-to-substrate distance. The obtained SnO₂ nanonetwork is in situ postannealed by a CO₂ laser to improve the crystallinity, while the nano morphology and grain size keep intact. To investigate the morphology and formation process of the nanonetwork, the microstructure of the laser-deposited SnO₂ layer is characterized. The crystallization control of CO₂ laser annealing is investigated through analyzing the Raman spectrum, X-ray diffraction (XRD) patterns, and lattice structures of the samples. By exposed to H₂ atmosphere, the fabricated gas sensor is demonstrated for H₂ monitoring.