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 Å. The particles were prepared via the gas-phase photolysis of a dilute ${\mathrm{Si}}_2$ ${\mathrm{H}}_6$/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 ${\mathrm{\Delta }}_1$ and ${\mathit{L}}_1$ 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 Å.