Self-organized gold nanostructures on Ge(001) surfaces are currently of special interest due to their applications for mono-molecular electronic devices and the growth of Ge nanowires. The understanding of electrical as well as physical properties of the system is of great importance and is strongly linked to its atomic structure.
Here, we report on studies concerning post-annealing induced nanostructure formation after room temperature deposition of a thin film of Au on Ge(001) in Ultra High Vaccuum (UHV). Deposition of 6 monolayers of Au by Molecular Beam Epitaxy (MBE) resulted in the formation of a continuous Au overlayer which was confirmed to be crystalline by Reflection High Energy Electron Diffraction (RHEED). Just after deposition, the samples were post-annealed in UHV to temperatures ranging from 473 K to 773 K with different cooling rates. The self-organized structures, in the form of Au nanoislands, were characterized by HR-SEM and HR-STEM methods as well as EBSD. It has been found that a preferential island orientation exists along the crystallographic direction of the substrate surface as can be seen in Fig. 1(a),(b). For an annealing temperature close to the eutectic temperature of the Au/Ge system (640 K), a change in size and shape of the Au nanoislands is observed as well as the occurence of the hexagonal phase of gold, indicating eutectic melting of the system as can be seen in Fig. 1. Au(011) orientation of the Au islands with respect to the Ge surface was revealed, independent of the annealing temperature Fig. 1(c),(d). TEM measurements of Au/Ge(001) sample cross sections revealed that the nanoislands created upon annealing at T640 K part of the islands are buried beneath the substrate surface (Fig. 1g), which confirms eutectic AuGe melting. The chemical composition of the Au/Ge interface was uncovered using quantitative atomically resolved HAADF-STEM and indicates the absence of alloying (Fig. 1f and 1h). The crystallographic structure of the Au islands and the presence of hexagonal gold as well as the Au/Ge interface were studied by quantitative atomically resolved HAADF-STEM allowing the determination of the structure.
N.G. and J.V. acknowledge funding from the European Research Council under the 7th Framework Program (FP7), ERC Starting Grant 278510 VORTEX. F.K. acknowledges funding from the Polish National Science Center, grant no. DEC-2012/07/B/ST5/00906. All authors acknowledge financial support from the European Union under the Seventh Framework Program under a contract for an Integrated Infrastructure Initiative (Reference No. 312483-ESTEEM2).
To cite this abstract:Nicolas Gauquelin, Benedykt Jany, Marek Nikiel, Tom Wilhammar, Karel van Den Bos, Sandra van Aert, Konrad Szajna, Johann Verbeeck, Gustaff Van Tendeloo, Franziszek Krok; Controlled production and growth of hexagonal gold nanostructures during self-assembly on a Ge(001) surface. The 16th European Microscopy Congress, Lyon, France. https://emc-proceedings.com/abstract/controlled-production-and-growth-of-hexagonal-gold-nanostructures-during-self-assembly-on-a-ge001-surface/. Accessed: December 12, 2018
EMC Abstracts - https://emc-proceedings.com/abstract/controlled-production-and-growth-of-hexagonal-gold-nanostructures-during-self-assembly-on-a-ge001-surface/