CAREER: Process-Structure-Property Relationships for Rational Engineering of Semiconductor Nanowires

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AbstractMichael A. Filler The long-range objective of this project is to establish foundational process-structure-property relationships for semiconductor nanowires and, in doing so, accelerate the timeline for realizing new nanowire-based photovoltaic device technologies. Real-time in-situ infrared spectroscopy measurements will be utilized to fundamentally interrogate the kinetics and thermodynamics that govern Si and Ge semiconductor nanowire growth. The specific experiments to be undertaken will test the hypothesis that surface chemistry can strongly influence crystal structure at multiple length scales. The PI seeks an atomic-scale understanding of precursor reactivity, adsorbate bonding, and surface structures such that growth processes can be rationally manipulated and structure precisely engineered. This chemical knowledge will also be connected to key optoelectronic properties via ex-situ absorption and electrical transport measurements. The fabrication of user-defined kinking, diameter, and doping-modulated superstructures will open new opportunities for efficient photon harvesting and charge carrier collection.Intellectual Merit: The combination of an ultrahigh vacuum growth environment and in-situ measurement limits nanowire degradation and yields a level of chemical detail not previously achievable. More specifically, it will be possible to definitively identify the transient surface chemistry that most strongly influences nanowire structure and properties. The specific bonding configuration of important surface species, either individually or in combination, will be distinguishable for the first time. While Si and Ge nanowires will serve as technologically relevant model systems, key findings will be broadly applicable to a range of materials classes (e.g. III-V semiconductors, oxides, etc.). Broader Impact: Breakthrough renewable energy technologies that could be widely deployed could transform our energy systems and dramatically reduce their carbon footprint. The insight gained during this work will enable the rational design of nanoscale components for next generation photovoltaic devices, making a contribution to the United States? declared goal of reducing carbon emissions over the coming years. Advancements are also expected to have broad application in a range of fields including photonics, electronics, quantum computation, and electrochemistry.Through this CAREER effort, the PI will significantly expand educational and outreach activities aimed at preparing the next generation of scientists and engineers for the impending shift to an energy sector based on renewables. At the undergraduate level, lecture modules will incorporate renewable energy fundamentals into the core chemical engineering curriculum. An upper-level course will provide a comprehensive treatment of the basic chemical science underlying solar energy capture, conversion, and storage. Yearly summer internships will allow local high school chemistry and physics teachers to work with the PI to create solar energy-related learning modules and hands-on demonstrations. The ?Prof. Solar? blog will be coupled with social networking services to disseminate recent scientific advances and introduce complex topics to a multidisciplinary audience.