Hot Carrier Dynamics at Ligated Silicon(111) Surfaces: A Computational Study.

Area of Science:

• Surface Science
• Computational Chemistry
• Materials Science

Background:

• Hydrogenated silicon surfaces are crucial for semiconductor applications.
• Understanding surface functionalization impacts electronic properties.
• Photophysics of silicon surfaces are key for optoelectronic devices.

Purpose of the Study:

• To investigate the thermal grafting of benzenediazonium bromide onto Si(111).
• To analyze the effect of phenyl group coverage on silicon surface photophysics.
• To elucidate the atomistic mechanisms governing excited-state dynamics.

Main Methods:

• Ab initio molecular dynamics (AIMD) for reaction pathway analysis.
• Calculation of nonadiabatic couplings using ab initio electronic structures.
• Application of reduced density matrix formalism with Redfield theory for excited-state dynamics.

Main Results:

• Identified reaction steps: N2 loss, HBr elimination, and phenyl group deposition.
• Phenyl-terminated Si(111) exhibits reduced nonradiative relaxation and recombination rates.
• Slower charge carrier cooling due to electron-phonon interactions observed.

Conclusions:

• Benzenediazonium bromide thermally decomposes to form covalently bonded phenyl groups on Si(111).
• Phenyl group coverage enhances photoluminescence efficiency in the near-infrared region.
• Surface functionalization with phenyl groups offers a pathway to tune silicon's optoelectronic properties.