Template-directed synthesis, characterization and electrical properties of Au–TiO2–Au heterojunction nanowires

The feasibility of synthesizing metal–oxide–metal (MOM) heterojunction nanowires in the Au–TiO2–Au system is demonstrated. The synthesis method presented here entails sequential electroplating of Au and electro-deposition of amorphous titanium oxide (TiOx ) inside nanoholes of anodic aluminium oxide (AAO) templates. This is followed by dissolving the template, and heat-treating the released nanowires, which results in the crystallization of the amorphous TiOx segment into nanocrystalline TiO2. Detailed transmission electron microscopy (TEM) investigation has revealed that the nanocrystalline TiO2 is orthorhombic (columbite) phase primarily. This synthesis method has the potential to provide better control over the characteristics and architectures of the resulting MOM nanowires. The Au–TiO2–Au nanowires were incorporated into single-nanowire devices, fabricated using a direct-write method. Nonlinear current–voltage (I–V ) responses were obtained for individual MOM nanowires. The heterojunctions in such MOM nanowires are likely to offer certain advantages over all-oxide nanowires, making the MOM nanowires potentially useful as one-dimensional building blocks in the multifunctional nanoelectronics of the future.