Surface Chemistry of Aerosolized Silicon Nanoparticles:  Evolution and Desorption of Hydrogen from 6-nm Diameter Particles

Abstract

The surface chemistry of pristine, 6-nm silicon nanoparticles has been investigated. The particles were produced in an RF plasma and studied using a tandem differential mobility analysis apparatus, Fourier transform infrared spectroscopy (FTIR), time-of-flight secondary ion mass spectrometry (ToF-SIMS), and transmission electron microscopy. Particles were extracted from the plasma, which operates at approximately 20 Torr, into an atmospheric pressure aerosol flow tube, and then through a variable-temperature furnace that could be adjusted between room temperature and 1200 degrees C. DMA measurements show that freshly generated silicon particles shrink with heating, with particle diameters decreasing by approximately 0.25 nm between 350 and 400 degrees C. FTIR results indicate that freshly generated particles are primarily covered with SiH2 groups and smaller amounts of SiH and SiH3. Spectra recorded as a function of heating temperature indicate that the amount of surface hydrogen, as measured by the intensity of modes associated with SiH, SiH2, and SiH3, decreases with heating. ToF-SIMS measurements also suggest that hydrogen desorbs from the particles surfaces over the same temperature range that the particles shrink.

Origin of the Photoluminescence Quantum Yields Enhanced by Alkane-Termination of Freestanding Silicon Nanocrystals: Temperature-Dependence of Optical Properties

“…The doublet is composed of two sets of absorption peaks. The first set centered at 895 cm −1 is attributed to the SiH 3 degenerate deformation and SiH 2 scissoring modes, while the second set centered at 859 cm −1 is assigned to the SiH 3 symmetric deformation and SiH 2 wagging modes35. All these bands are significantly diminished by the hydrosilylation, which instead exhibits characteristic C–H stretching and bending/scissoring bands at 2850–2960 and 1350–1500 cm −1  36.…”

Freestanding silicon nanocrystals with extremely low defect content

“…25 The spectrum of LIDD Si-NCs displays at 2000-2150 cm −1 a band with three components located at 2080, 2110, and 2141 cm −1 , attributed to Si-H stretching vibrations of Si 3 -Si-H, Si 2 -Si-H 2 , and Si-Si-H 3 surface hydride groups, respectively. 30,31 These three components have also been distinguished in the spectrum of MIDD Si-NCs, 25 but with different relative intensities. The LIDD Si-NCs exhibit a pronounced higher order hydride concentration due to the additional hydrogen injected into the afterglow of the synthesis plasma.…”

Aerosol synthesis of silicon nanoparticles with narrow size distribution—Part 1: Experimental investigations

“…5 shows characteristic bands for silicon with a partially hydrogenated/oxidized surface. The absorption bands at 2265, 2100, 887, 802 and 629 cm À 1 indicate the presence of Si-H x mono-and polyhydride groups (Holm & Roberts, 2007a, 2007b, which remain on the particle surface from the pyrolysis reaction of silane. It is known from literature, that the peak at 2265 cm À 1 is clearly attributed to Si-H x vibration mode with the presence of oxygen around the Si atom (Holm & Roberts, 2007a).…”