Annealing atmospheres induced structural and morphological transformation of zinc tin hydroxide nanostructures

The variation in crystallinity, morphology and phase of zinc tin hydroxide nanostructures are investigated after annealing at different (oxidizing, non-oxidizing and reducing) atmospheres. The zinc tin hydroxide nano-structures are prepared using hydrolysis assisted co-precipitation method. Annealing in oxidizing (oxygen and air) and non-oxidizing (nitrogen and argon) atmospheres do not have a significant effect on morphological and structural properties. However, the annealing in the reducing (ammonia) atmosphere converts the cubic nano-structures into nanorods and spherical particles. The zinc tin hydroxide forms three new phases (ZnON, SnO2 and Sn) after annealing in reducing atmosphere. The formation of ZnON and SnO2 phases are evident in Raman and XPS analysis. The reducing atmosphere (ammonia) changes the reaction kinetics leading to diffusion control crystal growth that could be responsible for such structural and morphological transformation. The bandgap is significantly changed after morphological and structural transformation with notable variation in photocurrent density, charge transfer resistance, and charge carrier concentration.