3D and 2D growth of SnO2 nanostructures on Ga2O3 nanowires: synthesis and structural characterization

Abstract

In this work, a simple thermal evaporation method has been used to obtain a variety of Ga₂O₃/SnO₂ nano-assemblies with different shapes and dimensionalities, which may affect their physical properties, especially those influenced by surface properties. The obtained nanostructures have been characterized using electron microscopy-related techniques in order to understand their growth mechanisms. By using both metallic gallium and tin oxide powders as precursors, Ga₂O₃ nanowires (straight or branched) decorated with SnO₂ nanoparticles or SnO₂ quasi-two dimensional plates have been produced after dynamic thermal annealing for 2.5, 8.0 and 15.0 hours. For shorter treatments, accumulation of Sn atoms at the Ga₂O₃ nanowire surface or defect planes has been observed by high resolution TEM, which suggests that they could act as nucleation sites for the further growth of SnO₂. On the other hand, longer treatments promote the formation of Ga-doped SnO₂ belts, from which SnO₂ nanowires eventually emerge. High-resolution TEM imaging and microanalysis reveal that Ga accumulation at (200) SnO₂ planes could stabilize some non-stoichiometric or intermediate tin oxide phases, such as Sn₂O₃, at local areas in the belts. The presence of non-stoichiometric tin oxide is relevant in applications, since surface states affect the physical–chemical behavior of tin oxide.