![]() Electron-Back-Scattered Diffraction (EBSD) and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). In our work, the Au hcp crystallite is present in each formed nanostructure as evidenced by electron microscopy i.e. The method we propose here gives the possibility to synthesize stable 3D Au hcp nanostructures with tunable size via thermally-induced Au self-assembly on a Ge(001) surface. The elastic constants for Au hcp were also calculated, confirming the possibility of fabricating pure and stable hcp Au under ambient conditions. 13, who has shown the possibility of hcp to fcc phase transition by first principle calculations. Nonetheless it was theoretically explored recently by Wang et al. Since this form of Au is so rare and very difficult to obtain, its properties were never studied. Only ~30% of the resulted nanoparticles were made of Au hcp phase. 11, 12 reported on synthesis of stable Au hcp nanoparticles on top of some germanium nanorods via quenching of Au/Ge liquid. It is important to remark that the Au hcp nanosheeets were reported by the authors to be unstable under electron irradiation reverting their structure to the conventional Au fcc phase 8, 9. Single-phase crystals of this unusual form of gold were solely obtained as graphene-supported nanometer-thick Au hcp sheets 8 or as nanoribbons 9 by wet chemistry synthesis, but so far little is known about its properties. The hexagonal closed packed ( hcp) structure of Au is a very rare form of gold as it naturally occurs in the cubic face centered ( fcc) phase. Gold is a noble material and has been extensively used in many areas of science and technology such as nanoelectronics 1, 2, catalysis 3, nanophotonics 4 and medicine 5, for its unique properties 6, 7 (non-reactive, highly conductive, biocompatible) over the last decades. This new method gives scientific prospects to obtain stable Au hcp phase for future applications in a rather simple manner as well as redefine the phase diagram of Gold with Germanium. ![]() We report that a careful heat treatment above the eutectic melting temperature and a controlled cooling is required to form the hcp phase of Au on a Ge single crystal. The Au hcp crystallite is present in each Au nanostructure and has been characterized by different electron microscopy techniques. Here, we show that stable hcp Au 3D nanostructures with well-defined crystallographic orientation and size can be systematically created in a process of thermally induced self-assembly of thin Au layer on Ge(001) monocrystal. It has also recently been synthesized in the form of thin graphene-supported sheets which are unstable under electron beam irradiation. ![]() Stable Au hcp phase has been reported to form in nanoparticles at the tips of some Ge nanowires. Gold crystallizes in the face-centered cubic ( fcc) phase, and its hexagonal closed packed ( hcp) structure is a very unusual and rare phase. ![]() Nano-sized gold has become an important material in various fields of science and technology, where control over the size and crystallography is desired to tailor the functionality. ![]()
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