Density functional theory study of Au-fcc/Ge and Au-hcp/Ge interfaces

Olga Sikora; Małgorzata Sternik; Benedykt R Jany; Franciszek Krok; Przemysław Piekarz; Andrzej M Oleś

doi:10.3762/bjnano.14.90

Density functional theory study of Au-fcc/Ge and Au-hcp/Ge interfaces

Beilstein J Nanotechnol. 2023 Nov 15:14:1093-1105. doi: 10.3762/bjnano.14.90. eCollection 2023.

Authors

Olga Sikora¹, Małgorzata Sternik², Benedykt R Jany³, Franciszek Krok³, Przemysław Piekarz², Andrzej M Oleś⁴

Affiliations

¹ Faculty of Materials Engineering and Physics, Cracow University of Technology, Podchorążych 1, PL-30084 Kraków, Poland.
² Institute of Nuclear Physics, Polish Academy of Sciences, W. E. Radzikowskiego 152, PL-31342 Kraków, Poland.
³ Marian Smoluchowski Institute of Physics, Faculty of Physics, Astronomy and Applied Computer Science, Jagiellonian University, Łojasiewicza 11, 30348 Krakow, Poland.
⁴ Institute of Theoretical Physics, Jagiellonian University, Prof. Stanisława Łojasiewicza 11, PL-30348 Kraków, Poland.

Abstract

In recent years, nanostructures with hexagonal polytypes of gold have been synthesised, opening new possibilities in nanoscience and nanotechnology. As bulk gold crystallizes in the fcc phase, surface effects can play an important role in stabilizing hexagonal gold nanostructures. Here, we investigate several heterostructures with Ge substrates, including the fcc and hcp phases of gold that have been observed experimentally. We determine and discuss their interfacial energies and optimized atomic arrangements, comparing the theory results with available experimental data. Our DFT calculations for the Au-fcc(011)/Ge(001) junction show how the presence of defects in the interface layer can help to stabilize the atomic pattern, consistent with microscopic images. Although the Au-hcp/Ge interface is characterized by a similar interface energy, it reveals large atomic displacements due to significant mismatch. Finally, analyzing the electronic properties, we demonstrate that Au/Ge systems have metallic character, but covalent-like bonding states between interfacial Ge and Au atoms are also present.

Keywords: Au/Ge heterostructures; density functional theory; electronic structure; hexagonal gold; interface energy.

Grants and funding

The authors kindly acknowledge support by the National Science Centre (NCN, Poland) under Projects No.: 2017/25/B/ST3/02586 (P.P. and M.S.), 2020/04/X/ST5/00539 (B.R.J.), and 2021/43/B/ST3/02166 (A.M.O.). A.M.O. is grateful for support via the Alexander von Humboldt Foundation Fellowship [37] (Humboldt-Forschungspreis). This research was supported in part by the Excellence Initiative – Research University Program at the Jagiellonian University in Kraków.