Growth kinetics of crumb-like structure formation on SnO₂ nanowires during direct oxidation

A facile AAO (anodic aluminum oxide) template-assisted vacuum die-casting technique was used to create Sn nanowires and convert them into SnO₂ without degrading the wires nanostructure. As a function of time and temperature, the controlled oxidation on the Sn nanowires of two different spatial configurations (100 and 250 nm in diameter) revealed distinct oxidation mechanisms. The 250-SnO₂ nanowires exhibits a peculiar crumb-like structure formation over the surface due to the higher level of Sn atom dislocation. Conversely, the sub-100 nm SnO₂ nanowires shows a highly crystalline, homogenous, and defect-free surfaces. The optical properties of the sub-100 nm SnO₂ nanowires were characterized using UV-Vis spectroscopy. The heat-treated tin oxides nanowires samples at temperatures of 300, 500, and 700 °C for 7 h exhibited optical energy bandgaps of 1.8, 2.6, and 3.3 eV, respectively. The observed variation in bandgap is attributed to the unique phase compositions achieved in each of the heat-treated samples. Moreover, the obtained results showed exceptional structural integrity and optical properties that are inherently interconnected with the diverse phases achieved under precise heat treatment conditions.