Session K5: Nanoscience

Digital Atomic Scale Fabrication

Nanotechnology has not lived up to its promises. An analogy could be made between the state of nanotechnology today and information technology when it was still analog. The vast majority of the growth of IT is due to digital information theory which was described by Shannon long before it was realized. We need to move from analog nanofabrication which treats matter as if it is infinitely divisible to a digital approach by using the tactics of digital IT that deal with the inevitable errors through a host of error detection and error correction schemes. The current and rapidly evolving IT systems are incredibly complex and yet extremely reliable. I believe that by embracing and developing digital tactics with our nanofabrication processes, similarly impressive nanosystems that are not restricted to information processing will emerge. I will describe our atomically precise patterning technique that achieves sub-nm resolution that is a fully digital fabrication technique and how we are developing atomic scale fabrication. I will describe how we can develop digital atomic scale fabrication that will tolerate fabrication errors and produce error-free structures. I am convinced that this is the most promising path to realizing the promises of nanotechnology.   

Electrical switching, loop hysteresis and charge oscillation in VO$_{\mathrm{\mathbf{2}}}$\textbf{ micro-channel devices}

Functional metal oxides are essential materials to realize novel electronic and optoelectronic devices with unique tunable characteristics. Vanadium dioxide (VO$_{\mathrm{2}})$ is of particular importance due to its well-known reversible metal-to-insulator phase transition which occurs at \textasciitilde 68\textdegree C temperature. In this work we investigated the electrical switching characteristics, loop hysteresis and negative differential resistance (NDR) of micro-channel devices using VO$_{\mathrm{2\thinspace }}$thin films deposited on sapphire ($c$-cut) substrates. The devices exhibited self-sustained charge oscillations with large amplitude modulation when connected to a DC power source and does not require any external capacitive or inductive components. We demonstrate that the device oscillation frequency can be systematically tuned by varying the optical power of a CW external laser source focused on the top of the VO$_{\mathrm{2}}$ micro-channels. This result is attributed to changes in electrical resistivity of the VO$_{\mathrm{2\thinspace }}$channel under illumination which in turn changes the NDR voltage width region and therefore the oscillation frequency.   

Effects of Nickel, Multi-walled Carbon Nanotubes, and Multi-walled Carbon Nanotubes/Nickel Nanoparticles on Power Production and Wastewater Treatment of Microbial Fuel Cells (MFCs)

Having an abundant amount of waste water makes it necessary to find a more effective way of treating water. Microbial fuel cells (MFCs) are a clean way of treating water that in the process produces clean electricity. The problem with this is that MFCs produce very low voltage and have not been developed to a greater scale. The purpose of this experiment is to coat the cathode electrode with different nanoparticles and hopefully reduce the internal resistance of the MFC, resulting in more power and cleaner wastewater. Methods and detections used in this study include electrochemical impedance spectroscopy, polarization curves, chemical oxygen demand tests, nanoparticle production by precipitation method and SEM/EDS for characterization. The result obtained was that the internal resistance was maximally reduced by 0.74 k$\Omega $ and the power density maximally increased by 1085.524 mW/m\textasciicircum 3.