Structure and Composition of Isolated Core-Shell(In,Ga)N/GaNRods Based on Nanofocus X-Ray Diffraction and Scanning Transmission Electron Microscopy
| Autor: | Achim Trampert, Michael Hanke, Zongzhe Cheng, Maik Kahnt, Christian G. Schroer, Andreas Waag, Lars Nicolai, Hergo-Heinrich Wehmann, Gerald Falkenberg, Hao Zhou, Michael Niehle, Jana Hartmann, Thilo Krause |
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| Rok vydání: | 2017 |
| Předmět: |
010302 applied physics
Diffraction Materials science Scattering Shell (structure) General Physics and Astronomy 02 engineering and technology 021001 nanoscience & nanotechnology 01 natural sciences Molecular physics Rod 0103 physical sciences X-ray crystallography Scanning transmission electron microscopy Relaxation (physics) Deformation (engineering) 0210 nano-technology |
| Zdroj: | Physical Review Applied. 7 |
| ISSN: | 2331-7019 |
| Popis: | Nanofocus x-ray diffraction is used to investigate the structure and local strain field of an isolated ðIn; GaÞN=GaN core-shell microrod. Because the high spatial resolution of the x-ray beam is only 80 × 90 nm2, we are able to investigate several distinct volumes on one individual side facet. Here, we find a drastic increase in thickness of the outer GaN shell along the rod height. Additionally, we performed highangle annular dark-field scanning-transmission-electron-microscopy measurements on several rods from the same sample showing that (In,Ga)N double-quantum-well and GaN barrier thicknesses also increase strongly along the height. Moreover, plastic relaxation is observed in the top part of the rod. Based on the experimentally obtained structural parameters, we simulate the strain-induced deformation using the finiteelement method, which serves as the input for subsequent kinematic scattering simulations. The simulations reveal a significant increase of elastic in-plane relaxation along the rod height. However, at a certain height, the occurrence of plastic relaxation yields a decrease of the elastic strain. Because of the experimentally obtained structural input for the finite-element simulations, we can exclude unknown structural influences on the strain distribution, and we are able to translate the elastic relaxation into an indium concentration which increases by a factor of 4 from the bottom to the height where plastic relaxation occurs. |
| Databáze: | OpenAIRE |
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