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Steric Effects on Single-Molecule Conductance in Flat-Lying Phenanthrene
Kevin Batzinger1, Qinghai Zhou2, Xiang Ye3
1Department of Physics, Binghamton University, Vestal, NY, USA.
The position of anchoring groups on phenanthrene (PHE) derivatives influences single-molecule conductance. When laid flat on a gold substrate, all PHE derivatives showed consistent conductance around 0.1 G0, regardless of anchoring group position.
Area of Science:
- Molecular electronics
- Quantum transport phenomena
Background:
- Previous studies indicated anchoring group position significantly impacts phenanthrene (PHE) derivative conductance.
- A consistent 0.1 G0 feature was observed across various PHE derivatives in prior research.
Purpose of the Study:
- To investigate the underlying reasons for the consistent 0.1 G0 conductance feature in PHE derivatives.
- To explore the influence of substrate interaction and tip positioning on PHE derivative conductance.
Main Methods:
- Simulated PHE derivatives on a gold substrate using a scanning tunneling microscope (STM) model.
- Calculated molecular conductance via non-equilibrium Green's function (NEGF) combined with density functional theory (DFT).
- Varied STM tip locations to identify optimal conductive and energetically favorable configurations.
Main Results:
- Optimal tip positions for maximal conductance and favorable energetics did not align.
- When PHE derivatives were positioned flat on the substrate, conductance variations observed in erect junctions disappeared.
- All flat-lying PHE derivatives exhibited calculated conductance values clustering around 0.1 G0.
Conclusions:
- The consistent 0.1 G0 conductance in flat-lying PHE derivatives suggests substrate interactions and tip placement are critical.
- The observed conductance is less sensitive to anchoring group position when PHE derivatives lie flat compared to erect configurations.
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