This proposal describes the correlation of the composition, strain, and electronic structure of group III-As nanowire core-shell heterostructures in three dimensions to understand how interactions between composition and strain influence nanostructure growth and optoelectronic properties. Atom probe tomography will be used to measure 3-D composition fields with nanoscale resolution. Based on these composition data, finite element models of relaxed physical structure will provide a foundation for simulations of and correlation with single nanowire x-ray imaging and diffraction, in partnership with domestic and international collaborators. Combined strain and composition data, including dopant distributions accessible only by atom probe tomography, will be used to model electronic and optical properties and identify materials factors that limit the performance of III-As core-shell nanowires as infrared light emitting diodes and lasers. Single nanowire Raman, photoluminescence, and electrical measurements will provide spatially resolved experimental data on strain, carrier concentrations and lifetimes, and the band offsets that establish confinement potentials. Complementary measurements of microstructure by collaborators provide a basis for “Total Tomography”. Intellectual Merit: The merit of establishing correlated composition and strain gradients in three dimensions at the nanoscale lies in the unique insights into processing-structure and structure-property relationships such data can provide. Specifically, the correlated atom probe and x-ray tomography will advance understanding of how composition, strain, and curvature influence the compositional uniformity of nonplanar heterostructures such as core shell semiconductor nanowires. Correlated atom probe, modeling, and property characterization will advance understanding of the materials characteristics, including strain, composition, and doping, that control the efficiency of spontaneous and stimulated emission under optical and electrical excitation. Furthermore, the correlated analysis platform to be developed will significantly advance the “total tomography” of non-planar heterostructures. Broader Impacts: Correlation of local strain and 3-D composition in III-As nanowire heterostructures will accelerate the development of materials for compact, efficient, Si-integrated infrared light emitting diodes, enabling on-chip photonic interconnects that overcome the bottleneck in the speed of information transfer within and between chips. The project will train graduate students in the cutting-edge and complementary methods of atom probe tomography and coherent x-ray diffraction, while developing modeling methodologies needed for such correlated measurements. In this way, the proposed research addresses significant barrier to the application of such methods in both basic and applied research. A web-based interactive case study will be developed to disseminate the methods and achieve impact beyond what is possible in print publications. In the classroom and at the department level home department, the PI is leading a multi-year effort to fully integrate modeling and simulation into the material science and engineering curriculum.
|Effective start/end date
|9/1/16 → 8/31/19
- National Science Foundation (DMR-1611341)
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