O₂ Oxidation and Sublimation Kinetics of Single Silicon Nanoparticles at 1200–2050 K: Variation of Reaction Rates, Evolution of Structural and Optical Properties, and the Active-to-Passive Transition

Abstract

Sublimation and O 2 etching kinetics for a series of individual silicon (Si) nanoparticles (NPs) were studied for NP temperatures (T NP ) from 1200 to 2050 K using a single NP mass spectrometry technique. Sublimation was significant for T NP > 1700 K, with rates reasonably well fit to Arrhenius kinetics but evolving, particularly during initial heating. O 2 etching efficiencies varied from NP-to-NP and with changing T NP , but they also evolved dramatically over time. For T NP ≤ 1500 K, NPs were observed to passivate after losing 30−50% of the initial NP mass. At higher T NP , etching efficiency decreased over time but never passivated. Interestingly, bulk Si passivation has not been observed for the range of T NP and O 2 pressures used here, and a model was developed to test the effects of several NP-specific mechanistic parameters on both the initial and time-dependent etching behavior. The optical properties of the hot NPs were also found to evolve as the NPs etched, particularly during the initial fast mass loss, and correlations between emission intensities and etching kinetics were examined.

High Temperature Reaction of Individual Graphite Nanoparticles with N2O: Etching, Passivation, Sublimation, and Comparison to O2

“…previously. 1,2,15,[27][28][29] In brief, graphite NPs (Alfa Aesar, 99.9999% metals basis) were injected into a quadrupole trap, 30 with 15 mTorr of ultrahigh purity (UHP) argon added to aid trapping.…”

High Temperature Reaction of Individual Graphite Nanoparticles with N2O: Etching, Passivation, Sublimation, and Comparison to O2

“…The single NP mass spectrometry method, along with methods for injecting NPs into the trap and for measuring NP mass ( M ), charge ( Q ), and temperature ( T NP ), has been described previously. ,,,− In brief, graphite NPs (Alfa Aesar, 99.9999% metals basis) were injected into a quadrupole trap, with 15 mTorr of ultrahigh-purity (UHP) argon added to aid trapping. The trap center was irradiated by a loosely focused 532 nm laser, and injection was stopped as soon as thermal emission was detected from an ∼50 μm volume at the trap center.…”