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Electron Transport Suppression from Tip-π State Interaction on Si(100)-2 × 1 Surfaces
K P Dou1,2, W Fan2, T A Niehaus3,4
1School of Physics, Shandong University, Jinan 250100, P.R. China.
Journal of Chemical Theory and Computation
|November 25, 2015
Summary
Electron transport in scanning tunneling microscopy (STM) on silicon surfaces changes dramatically with tip distance. At larger distances, conductance increases due to silicon dimer pi states, but decreases at closer distances as these states are suppressed.
Area of Science:
- Surface Science
- Condensed Matter Physics
- Materials Science
Background:
- Scanning tunneling microscopy (STM) is crucial for atomic-scale surface analysis.
- Understanding electron transport mechanisms is key to interpreting STM data.
- Silicon surfaces exhibit unique electronic properties relevant to nanoelectronics.
Purpose of the Study:
- To investigate electron transport mechanisms between an STM tip and Si(100)-2 × 1 surfaces.
- To determine how tip-surface distance influences conductance.
- To elucidate the role of surface electronic states in electron transport.
Main Methods:
- Density functional theory (DFT) calculations.
- Nonequilibrium Green's function (NEGF) method.
- Simulations of electron transport across varying tip-surface distances.
Main Results:
- Conductance mechanism shifts with tip-surface distance.
- At distances > 4.06 Å, conductance increases due to silicon dimer π states.
- At closer distances, π state suppression by the tip reduces conductance.
Conclusions:
- Tip-surface distance critically affects electron transport pathways.
- Silicon dimer π states are vital for conductance at larger tip separations.
- Tip-induced π state suppression dominates at close tip-surface proximity.
