Synthesis and characterization of metal and semiconductor nanowires

Cylindrical, metallic nanowires were electrochemically grown in nanochannels created in polymer membranes by etching of ion tracks. These nanowires consisted of Au or AuAg alloy with varying element ratio. In additon, segmented Au-rich/Ag-rich/Au-rich nanowires were synthesized by applying pulsed deposition. The duration of the pulses controls the length of the segments. By subsequent chemical dissolution nanowires separated by nanogaps with dimensions as small as 5 nm were also created, so-called nanowire dimers. Incomplete dissolution of the gap resulted in dimers connected by a conductive junction. Upon the excitation of surface plasmons in dimers separated by nanogaps smaller than 20 nm, high field enhancement is generated in the nanogap. We analysed the plasmonic properties of the synthesized structures by electron energy loss spectroscopy in a transmission electron microscope. This method enables the simultaneous investigation of the nanostructure morphology and the surface plasmon resonance energies. The analysis of single nanowires, and capacitively and conductively coupled nanowire dimers revealed that the resonance energies depend sensitively on many parameters, as length, diameter, gap size, as well as composition and morphology. Precise knowledge of the plasmonic properties of the synthesized structures are important for the future applications as substrates for surface enhanced infrared and Raman spectroscopy