In Situ Growth and Placement of Nanostructures by Solution-Based Processing

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Nanostructures are characterized by their tiny size - they are measured in nanometers, which are millionths of a millimeter. These tiny dimensions give them enhanced properties, which have applications in many technologies, from computers to cell phones to solar cells. One of the biggest challenges in the development of nanotechnology is the low-cost integration of nanostructures into commercial devices. Dr. Amy Walker (University of Texas at Dallas) addresses this problem by developing new methods to grow "in place" (in situ) nanowires, nanopores, nanorings, nanosheets and nanochannels made from transition metal chalcogenides, metal compounds containing sulfur or selenium. These materials are very promising for faster electronics, more efficient solar cells, new kinds of sensors and improved fuel cells. Her group specializes in solution-based methods which are cheaper and more environmentally friendly than conventional techniques. Dr. Walker uses a variety of experimental tools to study the growth and properties of nanostructures, in particular imaging mass spectrometry. This research is attractive to students at many levels. Both graduate and undergraduate students gain valuable expertise in her lab, going on to careers in the semiconductor, chemical and high-tech manufacturing industries. Dr. Walker involves students in electrochemistry, device design, nanoscience, surface and materials characterization, spectroscopy and mass spectrometry studies. In this work, Dr. Amy Walker (University of Texas at Dallas) is funded by the Macromolecular, Supermolecular and Nanochemistry (MSN) Program to develop new and scalable techniques used to synthesize metal chalcogenide nanostructures. Semiconductor nanowire deposition on micropatterned substrates (SENDOM) can create nanowires, nanopores, nanochannels and nanorings, which enables the fabrication of complex functional structures such as nanowire-based transistors. In SENDOM, a multifunctional micropatterned surface is used to direct the growth of nanostructures by chemical bath deposition (CBD). SENDOM is an in situ method that does not use complex lithography - these are significant advantages over other methods for nanostructures synthesis and placement. SENDOM relies on control of the interaction of CBD precursors and additives with organic thin films. Detailed mechanistic information about these interactions is also being leveraged to develop in situ solution-based techniques to selectively deposit and form free-standing transition metal dichalcogenides (TMDs) nanofilms. This research program substantially advances the state-of-the-art in nanotechnology by enabling the integration of nanostructures in practical devices. Finally, solution-based methods such as those used in this work are becoming increasingly important in "high-tech" industries, and Dr. Walker is developing educational modules to train students at all levels in this area.