Rational Engineering of Semiconductor Nanowire Crystal Structure for Next Generation Energy Conversion Devices

Georgia Tech Research Corporation, Atlanta GA

Investigators

Abstract

Proposal Number: 1133563 PI: Filler, Michael A. Intellectual Merit: The overarching research objective of this NSF proposal is to test the hypothesis that precise control of nanowire surface chemistry during growth can enable the rational engineering of semiconductor nanowire crystal structure. Successful validation of this hypothesis would improve the prospects for fabricating highly efficient nanowire-based photovoltaic and thermoelectric energy conversion devices. As opposed to the trial-and-error approaches that dominate the field, a custom-built in-situ infrared spectroscopic experimental platform will be utilized during these studies to fundamentally interrogate the chemistry that governs bottom-up semiconductor nanowire synthesis and structure. The combination of an ultrahigh vacuum growth environment and in-situ measurement is transformative in its ability to limit nanowire degradation and access a level of chemical detail not previously achievable. It will be possible to clearly distinguish which surface species or combinations of surface species, as well as what specific bonding structures, most strongly influence nanowire structure. Si nanowires serve as a technologically relevant model system and will be the focus of this work, but key findings will be broadly applicable to a range of important semiconductor nanomaterials. The specific objectives are three fold: (1) determine the role of surface-bound hydrogen on nanowire crystal orientation, (2) control nanowire crystal structure through the organic functionalization of nanowire sidewalls during growth, and (3) modulate nanowire structure as a function of axial position to create novel superstructures. Results from these objectives will collectively serve as the basis for semiconductor nanowire chemistry-structure and structure-property relationships that are essential for realizing devices with advanced performance. Preliminary data has demonstrated the importance of surface chemistry during nanowire growth and provides a strong foundation from which to begin this research effort. Broader Impact: Breakthrough photovoltaic and thermoelectric technologies that could be widely deployed could transform our energy systems and reduce their carbon footprint. The insight gained during this work will greatly accelerate the design of nanoscale components for next generation devices, making a significant contribution to the United States declared goal of reducing carbon emissions over the coming years. Although this effort will be focused on energy conversion, advancements are expected to have broad applicability in a range of fields including photonics, electronics, quantum computation, and electrochemistry. In addition, students at all levels of STEM education, as well as the general public, will be prepared to intelligently discuss and navigate the emerging renewable energy landscape. The use of the Internet and social networking tools will directly integrate key outreach efforts into the daily activities of a broad, multidisciplinary audience. In particular, the Prof. Solar blog will be used to disseminate recent scientific and technological advances via short video vignettes produced in a format that leverages everyday experiences in an educational and entertaining manner. The PI is also involved in local outreach activities that focus on underrepresented minority students at the K-12 level. These efforts will be continued and broadened through speaking engagements and hands-on scientific demonstrations. In addition, Georgia Tech undergraduate students will have opportunities to participate in research internships.