| Abstract
| - The earliest stages of thermal oxidation of 6 nm diameter silicon nanoparticles by molecular oxygen are examinedusing a tandem differential mobility analysis (TDMA) apparatus, Fourier-transform infrared (FTIR) spectroscopy,time-of-flight secondary ion mass spectroscopy (ToF-SIMS), and X-ray photoelectron spectroscopy (XPS). Particlesare synthesized in and then extracted from a nonthermal RF plasma operating at ∼20 Torr into the atmospheric pressureTDMA apparatus. The TDMA apparatus was used to measure oxidation-induced size changes over a broad range oftemperature settings and N2−O2 carrier gas composition. Surface chemistry changes are evaluated in situ with an FTIRspectrometer and a hybrid flow-through cell, and ex situ with ToF-SIMS and XPS. Particle size measurements showthat, at temperatures less than ∼500 °C, particles shrink regardless of the carrier gas oxygen concentration, while FTIRand ToF-SIMS spectra demonstrate a loss of hydrogen from the particles and minimal oxide formation. At highertemperatures, FTIR and XPS spectra indicate that an oxide forms which tends toward, but does not fully reach,stoichiometric SiO2 with increasing temperature. Between 500 and 800 °C, size measurements show a small increasein particle diameter with increasing carrier gas oxygen content and temperature. Above 800 °C, particle growth rapidlyreaches a plateau while FTIR and XPS spectra change little. ToF-SIMS signals associated with O−Si species alsoshow an increase in intensity at 800 °C.
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