Microscopy has played a central role in the advancement of nanoscience and nanotechnology by enabling the direct visualization of nanoscale structure, and by extension predictive models of novel physical behaviors. Correlated imaging of nanoscale structure and properties is an important frontier that can provide a rational basis for engineering new materials and devices. I will describe our approach to correlated imaging with a focus on semiconductor nanowires. Nanocrystal growth modes such as the vapor-liquid-solid process provide the ability to tailor nanoscale structure and composition in three dimensions, creating new opportunities in a range of applications including light harvesting and solid state lighting. In this context, we have explored a number of important processing-structure-property relationships using atom probe tomography [1,2], scanning transmission electron microscopy [3,4], Raman microspectroscopy [5,6] and scanning photocurrent microscopy . In addition, electromagnetic fields are visualized using finite difference time domain simulations. From these studies, we develop a more comprehensive understanding of the influence of geometry, size, defects, dopants, and interfaces on carrier generation, recombination, and transport in nanostructured materials. This quantitative approach to characterization of model systems aims to identify applications that can truly benefit from the adoption of unconventional nanostructured materials.
1. D. E. Perea et al “Direct Measurement of Dopant Distribution in an Individual Vapor-Liquid-Solid Nanowire,” Nature Nanotechnology 4, 315 (2009).
2. Atom Probe Tomography of a-Axis GaN Nanowires: Analysis of Facet Dependent Non-Stoichiometric Evaporation Behavior.” ACS Nano, in revision.
3. J. E. Allen et al, “High-resolution detection of Au catalyst atoms in silicon nanowires,” Nature Nanotechnology 3, 168 (2008).
4. E. R. Hemesath et al, “Catalyst incorporation at defects during nanowire growth.” Nano Letters 12, 167 (2012).
5. S. Zhang, J. Y. Chou, & L. J. Lauhon, “Direct Correlation of Structural Domain Formation with the Metal Insulator Transition in a VO2 Nanobeam,” Nano Letters 9, 4527 (2009).
6. F. J. Lopez et al, “Silicon nanowire polytypes: identification by Raman spectroscopy, generation mechanism, and misfit strain in homostructures,” ACS Nano 5, 8958 (2011).
7. Jerome K. Hyun and Lincoln J. Lauhon, “Spatially Resolved Plasmonically Enhanced Photocurrent from Au Nanoparticles on a Si Nanowire,” Nano Letters 11, 2731 (2011).