A microscale formaldehyde gas sensor based on Zn₂SnO₄/SnO₂ and produced by combining hydrothermal synthesis with post-synthetic heat treatment

A silicon-based micro-structure gas sensor for detecting formaldehyde was successfully fabricated and the sensing material was synthesized via a method of combining the traditional hydrothermal synthesis with subsequent heat treatment. Finite element analysis software of ANSYS was used to analyze the temperature distribution on the SiO₂/Si substrate with heating electrodes and signal electrodes on the same plane with the aim of reducing the complexity of micro-machining process. Meanwhile, in order to obtain lower power consumption, two different structures of the SiO₂/Si substrates with and without back etched were simulated, respectively. The simulation results showed that in the same heat rate and convection conditions, the back-etched SiO₂/Si substrate had higher temperature, more uniform temperature distribution, and lower energy consumption. The Zn₂SnO₄/SnO₂ cubes were obtained by annealing the as-synthesized precursors of ZnSn(OH)₆ at 700 °C for 3 h. Thermal gravimetric and differential thermal analyzer, X-ray diffraction, Fourier transform infrared spectra, scanning electron microscopy, and energy-dispersive X-ray spectroscopy were analyzed to characterize the phase structure, composition, morphology, and elemental atomic ratio of Zn₂SnO₄/SnO₂. The gas sensing properties of Zn₂SnO₄/SnO₂ were tested, which showed that the gas sensor based on Zn₂SnO₄/SnO₂ exhibited excellent formaldehyde sensing performance.