Electrochemical formation of one-dimensional metal nanostructures across microgaps electrodes for resistive switching and optical sensing applications.
This dissertation focuses on the electrochemical formation of one-dimensional (1D) Ag nanostructures (in particular nanowires and nanochains) directly on electrode surfaces or gap of two electrodes. Ag nanowires (NWs) and nanorods (NRs) grow directly on glass/indium tin oxide (ITO) surfaces from electrode-attached Au nanoparticle seeds in the presence of cetyltrimethylammonium bromide (CTAB) at appropriate potentials with a 5-15 % yield and the average length ranging from 100 nm to 3 µm for growth times of 30 to 120 min. This method failed when trying to grow Ag NRs/NWs across 5 µm Au electrode gaps. Interestingly, applying voltage in air leads to the formation of 1D Ag nanoparticle (Ag NP) chains across the electrode gap in the presence of CTAB and humidity. This is due to an electrochemical process of Ag oxidation at the positive electrode and reduction of Ag+ at the negative electrode of the gap. The 1D Ag NP chains have interesting resistive switching properties with ON/OFF ratio > 100, endurance cycles of at least 1000 and ms switching speeds, which could find use for memory devices. A device formed by electrodeposition of polyphenol on one electrode and Ag NWs on a second electrode of a 5 µm electrode gap also exhibits resistive switching properties similar to 1D Ag NP chains. Interestingly, the Ag NWs convert into Ag NP chains during the first connection. 1D Ag NP chains formed electrochemically in the presence of CTAB show interesting surface-enhanced Raman and localized surface plasmon resonance spectroscopy that depends on their conductance state.
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Electrochemical formation of one-dimensional metal nanostructures across microgaps electrodes for resistive switching and optical sensing applications.
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