Crystallographic Mapping of Guided Nanowires by Second-Harmonic Generation Polarimetry
2Physics of Complex Systems, Weizmann Institute of Science, Rehovot
The growth of horizontal nanowires (NWs) guided by epitaxial and graphoepitaxial relations with the substrate is becoming increasingly attractive owing to the posibility of controlling their position, direction and crystallographic orientation1-3. In guided NWs, as opposed to the extensively characterized vertically grown NWs, there is an increasing need for understanding the relation between structure and properties, specifically the role of the epitaxial relation with the substrate. Furthermore, the uniformity of crystallographic orientation along guided NWs and over the substrate has yet to be checked. Here we perform highly sensitive second-harmonic generation (SHG) polarimetry of polar and nonpolar guided ZnO. We optically map large areas on the substrate in a nondestructive way, and find that the crystallographic orientations of the guided NWs are highly selective and specific for each growth direction with respect to the substrate lattice. In addition, we perform SHG polarimetry along individual NWs and find that the crystallographic orientation is preserved along the NW in both polar and nonpolar NWs. However, while polar NWs show highly uniform SHG along their axis, nonpolar NWs show a significant change in the local nonlinear susceptibility along a few microns, reflected in a reduction of 40% in the ratio of the SHG along different crystal axes. We suggest that these differences may be related to strain accumulation along the nonpolar wires. We find that SHG polarimetry to be a powerful tool to study both selectivity and uniformity of crystallographic orientations of guided NWs with different epitaxial relations4.
References
1. Tsivion, D.; Schvartzman, M.; Popovitz-Biro, R.; von Huth, P.; Joselevich, E., Science 2011,
333, 1003-1007.
2. Tsivion, D.; Schvartzman, M.; Popovitz-Biro, R.; Joselevich, E., ACS Nano 2012, 6, 6433-
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3. Oksenberg, E.; Popovitz-Biro, R.; Rechav, K.; Joselevich, E.,. Adv Mater 2015, 27, 3999- 4005.
4. Neeman, L.; Ben-Zvi, R.; Rechav, K.;, Popovitz-Biro, R.; Oron, D,; Joselevich, E., Nano Lett. 2016 “under review”.
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