The electrical properties of tin dioxide (SnO2) nanoparticles induced by low calcination temperature were systematically investigated for gas sensing applications. The precipitation method was used to prepare SnO2 powders, while the sol-gel method was adopted to prepare SnO2 thin films at different calcination temperatures. The characterization was done by X-ray diffraction, scanning electron microscopy (SEM), and atomic force microscopy (AFM). The samples were perfectly matched with the rutile tetragonal structure. The average crystallite sizes of SnO2 powders were 45 ± 2, 50 ± 2, 62 ± 2, and 65 ± 2 nm at calcination temperatures of 300, 350, 400, and 450°C, respectively. SEM images and AFM topographies showed an increase in particle size and roughness with the rise in calcination temperature. The dielectric constant decreased with the increase in the frequency of the applied signals but increased on increasing calcination temperature. By using the UV-Vis spectrum, the direct energy bandgaps of SnO2 thin films were found as 4.85, 4.80, 4.75, and 4.10 eV for 300, 350, 400, and 450°C, respectively. Low calcination temperature as 300°C allows smaller crystallite sizes and lower dielectric constants but increases the surface roughness of SnO2, while lattice strain remains independent. Thus, low calcination temperatures of SnO2 are promising for electronic devices like gas sensors.
Achieving ultra-large elastic strains in Nb thin films on NiTi phase-transforming substrate by the principle of lattice strain matching
