Sequential physical vapor deposition and chemical vapor deposition for the growth of In2O3-SnO2 radial and longitudinal heterojunctions

Heterostructures of In2O3 and SnO2 were produced by sequential application of the physical- and chemical-vapor deposition techniques usually adopted for nanowire fabrication. In2O3 nanowires exhibit a single crystal body-centered cubic structure oriented along the [1 0 0] direction and grow epitaxially on α-sapphire substrate by means of a transport and condensation method assisted by Au nanoparticles. Nucleation and growth occurred via direct vapor solid (VS) mechanism competing with catalyst-mediated vapor-liquid-solid (VLS). SnO2 nanowires were obtained in a single crystal tetragonal (cassiterite) structure and oriented along the [1 0 1] direction, the growth being promoted by the gold particle at the apex of the In2O3 nanowires. The size of the catalyst thereby determines the main morphological features of SnO2 wires. CVD deposition allows precise control of the geometrical features of the heterojunction, also limiting detrimental nucleation of SnO2 on the lateral sides of In2O3 nanowires due to lower longitudinal growth rate. These results can help in improving the ability of finely tuning the morphological and structural properties of heterostructured oxide nanocrystals.