Preparation of oxide quasi 1d structures
The increasing scientific interest in 1-D systems such as nanowires and nanorods stimulates their functional exploitation, and single-crystalline 1-D nanostructures are nowadays emerging as building blocks for a new generation of electronic, and optoelectronic nanometer-scaled devices with superior performances. The potential of the bottom-up approach for the preparation of a new generation of size- and shape- controlled nanostructured materials has been demonstrated for a number of pure oxides. The fabrication techniques of homogeneous 1-D nanostructures have pursued the control over shape, aspect-ratio, and the crystalline arrangement to a considerable degree, and the improvement of the synthesis methods has recently achieved the fabrication of chemically non-homogeneous 1-D nanowires, heterogeneous structures, and eventually the direct integration of functional nanostructures into nano-devices.
At SENSOR we synthesize and characterize quasi monodimensional single crystals of Zn, Sn, Cu and In oxide nanowires (NWs) by Physical and Chemical Vapour Deposition (PVD and CVD) techniques (Figure 1). Thermal evaporation of oxide or precursors powders under controlled conditions is obtained in tubular furnaces at low pressure. Hierarchical structures of metal oxides were obtained by several deposition steps, using catalyst assisted process.Furthermore liquid phase growth techniques are have been studied for the preparation of Zn and Cu oxide nanostructures. We have obtained Cu2O bi-pyramids by reduction of Cu(OH)2 using hydrazine as reducing agent.
We used electrochemical anodization to prepare oxides as quasi 1D structures. The surface of metal can be easily and cheaply oxidized and modified by electrochemical anodization method. Anodization of titanium foils and thin films on solid and polymeric flexible substrates were performed using a two-electrode electrochemical cell. The morphology and shape of resulting anodized titanium is strongly dependent on the experimental conditions such as the type and concentration of electrolytes, the applied voltage and current, the temperature, the anodization time (Figure 2).The prepared nanostructrure are then fully characterised in terms of morphological, structural, electrical and optical properties in form of bundles, vertically aligned NWs and single NW transistors.