Phase separation in single In(x)Ga(1-x)N nanowires revealed through a hard X-ray synchrotron nanoprobe

• Published in: Nano letters 2014-03, Vol.14 (3), p.1300
• Main Authors: Segura-Ruiz, J, Martínez-Criado, G, Denker, C, Malindretos, J, Rizzi, A
• Format: Article
• Language: English
• Subjects: Gallium - chemistry; Indium - chemistry; Nanowires - chemistry; Nanowires - ultrastructure; Synchrotrons; X-Rays
• ISSN: 1530-6992
• DOI: 10.1021/nl4042752

In this work, we report on the composition, short- and long-range structural order of single molecular beam epitaxy grown In(x)Ga(1-x)N nanowires using a hard X-ray synchrotron nanoprobe. Nano-X-ray fluorescence mapping reveals an axial and radial heterogeneous elemental distribution in the single wires with Ga accumulation at their bottom and outer regions. Polarization-dependent nano-X-ray absorption near edge structure demonstrates that despite the elemental modulation, the tetrahedral order around the Ga atoms remains along the nanowires. Nano-X-ray diffraction mapping on single nanowires shows the existence of at least three different phases at their bottom: an In-poor shell and two In-rich phases. The alloy homogenizes toward the top of the wires, where a single In-rich phase is observed. No signatures of In-metallic precipitates are observed in the diffraction spectra. The In-content along the single nanowires estimated from X-ray fluorescence and diffraction data are in good agreement. A rough picture of these phenomena is briefly presented. We anticipate that this methodology will contribute to a greater understanding of the underlying growth concepts not only of nanowires but also of many nanostructures in materials science.