Oxide–oxide nanojunctions in coaxial SnO2/TiO2, SnO2/V2O3 and SnO2/(Ti0.5V0.5)2O3 nanowire heterostructures

A single-crystalline shell based on titanium and vanadium binary oxides with karelianite structure (Ti1−xVx)2O3 was successfully deposited onto SnO2 nanowires by sequential chemical vapor deposition (CVD). In comparison to single titanium or vanadium oxide shells, the binary Ti–V metal oxide overlayer overcomes the problems related to lattice mismatch and thermochemical stability, which usually take place in coaxial oxide–oxide heterostructures due to the atomic diffusion between core and shell. The modulation of the titanium content in the binary (Ti1−xVx)2O3 karelianite shell results in a lower mismatch (∼1.5%) and improves the epitaxial relationship with the rutile lattice of SnO2 core nanowires. Therefore, the presence of defects such as dislocations and strain fields, which in principle limit the carrier transport properties affecting the electrical, optical and photocatalytic performance, is strongly reduced. Atomic model simulations confirm that structural characteristics related to lattice mismatch and strain accommodation at the heterojunction influence the thermochemical stability and were corroborated by detailed high resolution transmission electron microscopy analyses of the different core–shell systems.