We employ a variety of nanocharacterization techniques to understand and ultimately improve the nanowire properties. For example, spatially-resolved cathodoluminescence experiments are being used to map the frequencies and intensities of light emission from these nanowires with nanoscale resolution, as shown in the accompanying figure. This and other optical techniques that have with our collaborators been adapted to studying these nanostructures, including 3D electron tomography, near-field scanning microscopy and ultrafast and deep-level optical spectroscopies, have revealed details such as the origin and concentration of impurities and other point defects in the nanowires, with the goal of reducing them and their impact on nanowire-based devices.
Q. M. Li, G. T. Wang, "Strain influenced indium composition distribution in GaN/InGaN core-shell nanowires", Appl. Phys. Lett., 97, 181107 2010.[link]
A. Armstrong, Q. Li, Y. Lin, A. A. Talin, G. T. Wang, "GaN nanowire surface state observed using deep level optical spectroscopy", Appl. Phys. Lett., 96, 2010. [link]
Q. M. Li, G. T. Wang, "Spatial Distribution of Defect Luminescence in GaN Nanowires", Nano Lett., 10, 1554 2010. [link]
I. Arslan, A. A. Talin, and G. T. Wang, “Three-Dimensional Visualization of Surface Defects in Core-Shell Nanowires,” Journal of Physical Chemistry C 112, 11093–11097 (2008). [link]
Showing multi-color InGaN emission
3D scanning transmission electron microscopy (TEM)
GaN/AlGaN/GaN Double heterostructure nanowire