Undulated silicene and germanene freestanding layers: why not?
M-C Hanf1,2, A Marjaoui1,2,3, R Stephan1,2
1Université de Haute Alsace, CNRS, IS2M UMR7361,68100 Mulhouse, France.
Summary
Freestanding silicene and germanene layers can form ripples at 0 K without strain. These ripples, with low energy costs, alter the electronic structure and open a band gap in germanene.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Computational Chemistry
Background:
- Silicene and germanene are typically modeled as honeycomb lattices with inherent layer buckling.
- Understanding the structural dynamics of these 2D materials is crucial for their electronic applications.
Purpose of the Study:
- To investigate the possibility of rippling in freestanding silicene and germanene layers at 0 K.
- To determine the energetic cost and structural characteristics of these ripples.
- To analyze the impact of ripples on the electronic band structure.
Main Methods:
- First-principles calculations were employed to simulate silicene and germanene.
- Structural stability and electronic properties were analyzed under rippling conditions.
- Analysis included bond angle modifications and energy calculations per atom.
Main Results:
- Silicene and germanene exhibit stable rippled structures at 0 K without requiring compressive strain.
- Significant undulations were observed in germanene, with height differences up to 4.7 Å for a wavelength of 81 Å.
- The energy cost for these deformations is low (0.1–0.8 meV/atom), associated with minor bond angle changes (<1.7°).
Conclusions:
- Freestanding silicene and germanene can intrinsically form ripples, offering new structural possibilities.
- These ripples significantly modify the electronic band structure, notably opening a 15 meV band gap in germanene.
- The low energy cost and tunable electronic properties suggest potential for novel electronic device applications.
