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

• Published in: Journal of the American Chemical Society 2007-03, Vol.129 (9), p.2496-2503
• Main Authors: Holm, Jason, Roberts, Jeffrey T
• Format: Article
• Language: English
• Subjects: Aerosols - chemistry; Hydrogen - chemistry; Mass Spectrometry; Microscopy, Electron, Transmission; Nanoparticles; Particle Size; Silicon - chemistry; Spectroscopy, Fourier Transform Infrared; Surface Properties; Temperature
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja0658970

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 ∼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 °C. DMA measurements show that freshly generated silicon particles shrink with heating, with particle diameters decreasing by ∼0.25 nm between 350 and 400 °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.