Measuring Dopant-Modulated Vibrational Energy Transfer over the Surface of Silicon Nanoparticles by 2D-IR Spectroscopy

2D-IR spectroscopy was used to characterize the vibrational dynamics of surface hydride modes on silicon nanoparticles (SiNPs). Energy transfer was compared between undoped (intrinsic) SiNPs and particles that were doped with boron and phosphorus. FTIR spectra reported changes in the relative proportions of Si-H, Si-H₂, and Si-H₃ populations when boron and phosphorus atoms were incorporated, while 2D-IR spectroscopy revealed that there was vibrational energy transfer on the tens of ps time scale between all three mode types for intrinsic SiNPs. This energy transfer was severely diminished by including just 0.05 atomic % of boron and was completely extinguished for 2.5 atomic % of phosphorus. In addition, the vibrational lifetimes of mono and polyhydride modes on intrinsic silicon particles were uniformly fast, while doped nanoparticles showed frequency dependent relaxation times reminiscent of porous and amorphous silicon films.