THE EFFECT OF ULTRATHIN OXIDES ON LUMINESCENT SILICON NANOCRYSTALLITES

The effect of ultrathin oxides on nanocrystallites of luminescent poro us silicon is studied using infrared, optical, and Auger spectroscopy. Room-temperature oxidation is performed using H2O2 immersion and UV o zone interactions, producing oxides of similar to 5 and similar to 10 Angstrom, respectively. The H2O2 oxidized sample is optically active, while the ozone oxidized sample is not active. UV-ozone produces a tra nsverse optical Si-O-Si mode blueshifted by similar to 90 cm(-1) from bulk oxide, which H2O2 does not produce. Auger Si LVV spectra show an oxidelike signal for UV/ozone samples and a Si-like signal for H2O2 sa mples. We discuss this in terms of different oxidation behaviors that either preserve or break Si-Si dimers that may be responsible for the optical behavior. (C) 1998 American Institute of Physics.