Substrate-induced structures of bismuth adsorption on graphene: a first principles study

Area of Science:

• Surface science
• Condensed matter physics
• Materials science

Background:

• Graphene's unique electronic properties are sensitive to adsorbates and substrates.
• Understanding bismuth (Bi) adatom behavior on graphene is crucial for novel electronic devices.

Purpose of the Study:

• Investigate the geometric and electronic properties of Bi-adsorbed monolayer graphene on a substrate.
• Determine the stable adatom arrangements and their formation mechanisms.
• Correlate theoretical findings with experimental measurements.

Main Methods:

• First-principles calculations were employed to simulate a six-layered substrate, a corrugated buffer layer, and monolayer graphene.
• Analyzed ground-state energies, adsorption energies, and inter-adatom interaction energies.
• Studied various adatom configurations, including height, distance, and site.

Main Results:

• A hexagonal array of Bi atoms is favored due to buffer layer-graphene interactions.
• An energy barrier of ~50 meV can be overcome by temperature, forming triangular and rectangular nanoclusters.
• Calculated density of states show a finite value at the Fermi level, a dip at -0.2 eV, and a peak at -0.6 eV.

Conclusions:

• The simulated stable and metastable Bi adatom structures align with scanning tunneling microscopy measurements.
• The electronic properties, including density of states, are consistent with experimental tunneling conductance data.
• Substrate effects significantly influence Bi adsorption and nanocluster formation on graphene.