Accommodating a hexagonal ζ- phase Mn2N film on a cubic MgO (001) substrate

• Published in: Applied surface science 2024-08, Vol.664 (C), p.160152, Article 160152
• Main Authors: Shrestha, Ashok, Hernandez, Juan Carlos Moreno, Abbas, Ali, Cocoletzi, Gregorio Hernandez, Takeuchi, Noboru, Ingram, David C., Smith, Arthur R.
• Format: Article
• Language: English
• Subjects: Density functional theory; Scanning tunneling microscope; Surface reconstruction; ζ- phase Mn2N
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2024.160152

The thin films of c-plane dominated hexagonal ζ- phase Mn2N were successfully grown on a cubic MgO (001) substrate directly using plasma-assisted molecular beam epitaxy. The surface was comprehensively studied through experimental and theoretical approaches. Reflection high energy electron diffraction revealed two pseudo-cubic domains along [100]MgO and [110]MgO, and one hexagonal domain, which is 30° apart from the [100]MgO direction. Scanning tunneling microscopy was used to image and resolve the high quality surface, revealing a distorted hexagonal surface structure. Furthermore, atomic resolution of the hexagonal domain with a 2 × 2 reconstructed surface is presented. For the c-plane surface, theoretical investigations were carried out using first-principle studies to determine the surface formation energy for various reconstructed surfaces. The theoretical study shows that the nitrogen terminated 2 × 2 structure with a manganese adatom on the surface is the most stable reconstruction that reproduces the experimental results. A corresponding simulated scanning tunneling microscopy model is also presented, providing strong support for the experimentally observed in-plane lattice structures. The manganese:nitrogen stoichiometry within the bulk and surface is in good agreement with the expected ratio of 2:1. [Display omitted] •Heteroepitaxial growth of Mn2N on cubic substrate.•Film grown on cubic substrate isn't always constrained to maintain cubic symmetry.•Crystal structure accommodated on symmetry mismatched substrate in various ways.•STM images reveal 2 × 2 reconstructed pseudo-cubic and hexagonal domains.•N-terminated Mn ad-atom model corresponds to the most stable Mn2N surface.