The effect of ultrathin oxides on luminescent silicon nanocrystallites

Abstract

The effect of ultrathin oxides on nanocrystallites of luminescent porous silicon is studied using infrared, optical, and Auger spectroscopy. Room-temperature oxidation is performed using H2O2 immersion and UV ozone interactions, producing oxides of ∼5 and ∼10 Å, respectively. The H2O2 oxidized sample is optically active, while the ozone oxidized sample is not active. UV–ozone produces a transverse optical Si–O–Si mode blueshifted by ∼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 samples. 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.