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 angstrom. The particles were prepared via the gas-phase photolysis of a dilute Si2H6/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 DELTA1 and L1 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 angstrom.