The Ground State of Epitaxial Germanene on Ag(111)

Abstract

Two-dimensional (2D) honeycomb lattices beyond graphene, such as germanene, appear very promising due to their outstanding electronic properties, such as the quantum spin Hall effects. While there have been many claims of germanene monolayers up to now, no experimental evidence of a honeycomb structure has been provided up to now for these grown monolayers. Using scanning tunneling microscopy (STM), surface X-ray diffraction (SXRD), and density functional theory, we have elucidated the Ge-induced reconstruction on Ag(111). We demonstrate that a powerful algorithm combining SXRD with STM allows us to solve a giant surface reconstruction with more than a hundred atoms per unit cell. Its extensive unit cell indeed consists of 98 2-fold or 3-fold coordinated Ge atoms, forming a periodic arrangement of pentagons, hexagons, and heptagons, with the inclusion of six dispersed Ag atoms. By analogy, we show that the reconstruction obtained by segregation of Ge through an epitaxial Ag/Ge(111) film possesses a similar structure, i.e., Ge pentagons/hexagons/heptagons with a few Ag atoms. Such an organization is more stable than that of pure Ge monolayers and can be assigned to the ground state of epitaxial germanene.

Letter to the Editor Concerning “The Ground State of Epitaxial Germanene on Ag(111)”

“…In Figure a scanning tunneling image of germanene taken from the aforementioned reference is shown. We would like to emphasize that the observed buckling of germanene’s honeycomb lattice , is in agreement with theoretical predictions. , Finally, Zhang et al also state in the introduction section of their article that the findings in many germanene manuscripts, including ours, are questioned. This statement is also incorrect, as our work has not been questioned.…”

“…In a recent article by Zhang et al in ACS Nano , the authors write in the abstract of their article that there are many claims of the realization of germanene (the germanium analogue of graphene) but that no experimental evidence for the honeycomb structure of this two-dimensional material has been provided. This statement is incorrect.…”

Mechanical characteristics and thermal conductivity of defect single-layer buckled honeycomb germanene

“…In addition, in the armchair-shaped direction, because phonons scatter less along the out-of-plane vibration, the armchair's thermal conductivity of the shape is higher. At a fixed length and width, if the temperature increases, the probability of collision between phonons increases, which increases the probability of phonon scattering by the boundary, and k is proportional to T, the mean free path is fixed [15], increasing the thermal conductivity coefficient. At higher temperatures, phonons exhibit Umklapp scattering, and the thermal conductivity coefficient decreases with increasing temperature because the mean free path is inversely proportional to temperature.…”

“…Recently, inspired by the fruitful results of graphene and silicone, strong research interest has been attracted to another group of IV element honeycomb materials, germanene [13]. Germanene is a two-dimensional (2D) material with a honeycomb structure [14], and it has attracted wide attention for its high carrier mobility [15][16][17]. Due to the buckling of the honeycomb lattice caused by the Ge-Ge bond length, the spin-orbit gap in single-layer germanium (24 meV) is larger than that of graphene (< 0.05 meV) and other carbon series structures [18,19].…”

Reply to the Comment on “The Ground State of Epitaxial Germanene on Ag(111)”

“…In their comment, Pantelis Bampoulis and Harold J. W. Zandvliet focus on how their results are presented in the introduction of our paper intitled “The ground state of epitaxial germanene on Ag(111)” …”