Synthesis of High Purity Silicon Nanoparticles in a Low Pressure Microwave Reactor

Abstract

The formation of pure single crystalline silicon nanoparticles by microwave induced decomposition of silane in a low pressure flow reactor is reported. The morphology and crystal structure of the particles are characterized in situ by particle mass spectrometry (PMS) and ex situ by means of X-ray diffraction, high resolution transmission electron microscopy, electron energy loss spectroscopy, and infrared spectroscopy. The preparation method allows for the adjustment of the mean particle diameter in the range 6 nm < or = dPM < or = 11 nm by controlling the precursor concentration, gas pressure, and microwave power. Spectroscopic investigations reveal that the particles are single crystal silicon. The potential on n- or p-type doping is in progress.

Role of Structural Order and Excess Energy on Ultrafast Free Charge Generation in Hybrid Polythiophene/Si Photovoltaics Probed in Real Time by Near-Infrared Broadband Transient Absorption

“…40 The pressure of the process gases and the microwave power determine the mean diameter of the Si-ncs. Phosphorus doping of the Si-ncs was achieved by adding phosphine during growth and increases the carrier mobility in the Si-ncs.…”

Microwave Plasma Synthesis of Materials—From Physics and Chemistry to Nanoparticles: A Materials Scientist’s Viewpoint

“…Janzen et al [72] and Thekedar [80] show this behavior for Fe 2 O 3 nanoparticles, Kleinwechter et al [73] for ZnO nanoparticles, Knipping et al [81] for Si nanoparticles, Thekedar [80] for SiO 2 nanoparticles, and Shimada et al [82] for GaN nanoparticles. In all cases measured particle sizes are below 10 nm.…”

“…For different synthesized materials, several research groups find comparable behavior for the dependency of nanoparticle sizes from the precursor concentration using different 2.45 GHz equipment. Mostly investigated are the particle sizes of Fe 2 O 3 [72,80], Si [49,81], SiO 2 [80], GaN [82] and SnO 2 [83] nanoparticles as a function of precursor concentration. In all cases, the observed particle, respectively the crystallite sizes, do not exceed 12 nm (p. 288 in [21]).…”

“…With increasing pressure a linear increase of the diameter of the nanoparticles is observed for Si [81], ZnO [73], SiO 2 [80], and Al 2 O 3 [85] nanoparticles from several groups. This behavior can be explained by the increased collision probability, leading to enhanced nanoparticle growth.…”

“…The larger the particle diameters are, and the higher their mass is, the better they can be collected via thermophoresis. Mechanical filtering [81,92] or cyclones [93,94] are alternative collection methods for nanoscaled powders. A common method for deposition of small charged particles from the gas phase is electrostatic deposition [95,96].…”