Electron energy loss spectroscopy of single silicon nanocrystals: The conduction band

Spatially resolved electron energy loss spectroscopy has been performed on single, H-terminated, Si nanocrystals in the size range 25--500 {}. The particles were prepared via the gas-phase photolysis of a dilute Si₂{H}₆$/He mixture in a gas flow cell, and deposited on a holey carbon grid for analysis. Energy loss within a few eV of the core 2p ionization edge reveals information about the conduction band states at ${{{Δ}}}₁$ and ${L}₁$ in the Brillouin zone. The conduction band edge is observed to shift to higher energy as the inverse square of the particle radius. In addition, a strong increase in the oscillator strength for these transitions is observed for decreasing particle sizes below 60 {}.