Atomic structural analysis of nanowire defects and polytypes enabled through cross-sectional lattice imaging.

Correlated transmission electron microscopy imaging, electron diffraction, and Raman spectroscopy are used to investigate the structure of Si nanowires with planar defects. In addition to plan-view imaging, individual defective nanowires are imaged in axial cross-section at specific locations selected in plan-view imaging. This correlated characterization approach enables definitive identification of complex defect structures that give rise to diffraction patterns that have been misinterpreted in the literature. Conclusive evidence for the 9R Si polytype is presented, and the atomic structure of this phase is correlated with kinematically-forbidden reflections in Si diffraction patterns. Despite striking similarities between imaging and diffraction data from twinned nanowires and the 9R polytype, clear distinctions between the structures can be made. Finally, the structural origins of ⅓{422} reflections in Si [111] diffraction patterns are identified.