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Doping of the hydrogen-passivated Si(100) electronic structure through carborane adsorption studied using density
Martin Hladík1, Antonín Fejfar1, Héctor Vázquez1
1Institute of Physics, Academy of Sciences of the Czech Republic, Cukrovarnická 10, 162 00 Prague, Czech Republic. hladikm@fzu.cz.
Physical Chemistry Chemical Physics : PCCP
|September 7, 2021
Summary
Dithiocarborane molecules can dope silicon non-destructively by forming stable bonds with hydrogen-passivated Si(100) surfaces. This molecular doping strategy offers a promising approach for semiconductor applications by reducing the hole injection barrier without creating interface gap states.
Area of Science:
- Materials Science
- Surface Science
- Semiconductor Physics
Background:
- Non-destructive doping of silicon is crucial for advanced semiconductor devices.
- Tailored molecular adsorbates offer a novel approach to surface functionalization.
- Dithiocarboranes exhibit large permanent dipoles and form stable monolayers.
Purpose of the Study:
- To investigate the doping of hydrogen-passivated Si(100) via dithiocarborane adsorption.
- To characterize the bonding, stability, and electronic properties of the Si-dithiocarborane interface.
- To assess the potential of molecular adsorbates for non-destructive semiconductor doping.
Main Methods:
- Density Functional Theory (DFT) calculations for electronic structure and bonding.
- Physisorption and chemisorption analysis.
- Mechanical and thermal stability characterization.
- Molecular dynamics simulations for room-temperature stability.
Main Results:
- Dithiocarboranes can both physisorb and chemisorb on Si(100), with chemisorption involving S-H replacement.
- Stable Si-molecule bonds are formed with significant mechanical and thermal stability.
- Adsorption does not introduce interface gap states; band gap remains largely unchanged.
- A 0.3 eV downward shift in Si spectral features reduces the hole injection barrier.
Conclusions:
- Chemisorption of dithiocarboranes provides a stable and non-destructive method for doping silicon.
- The large electrostatic dipole of dithiocarboranes effectively modifies the semiconductor's electronic properties.
- This molecular doping strategy is stable at room temperature, showing promise for future semiconductor technologies.
