Production of nanometric particles in radio frequency glow discharges in mixtures of silane and methane
01 Mar 1996-Journal of Vacuum Science and Technology (American Institute of Physics)-Vol. 14, Iss: 2, pp 567-571
TL;DR: In this paper, the a−Si1−xCx:H powders were obtained from different precursor gas mixtures, from R=0.05 to R=9, where R=[SiH4]/([SiH 4]+[CH4])...
Abstract: The formation of silicon particles in rf glow discharges has attracted attention due to their effect as a contaminant during film deposition or etching. However, silicon and silicon alloy powders produced by plasma‐enhanced chemical vapor deposition (PECVD) are promising new materials for sintering ceramics, for making nanoscale filters, or for supporting catalytic surfaces. Common characteristics of these powders are their high purity and the easy control of their stoichiometry through the composition of the precursor gas mixture. Plasma parameters also influence their structure. Nanometric powders of silicon–carbon alloys exhibiting microstructural properties such as large hydrogen content and high surface/volume ratio have been produced in a PECVD reactor using mixtures of silane and methane at low pressure (<1 Torr) and low frequency square‐wave modulated rf power (13.56 MHz). The a‐Si1−xCx:H powders were obtained from different precursor gas mixtures, from R=0.05 to R=9, where R=[SiH4]/([SiH4]+[CH4])...
TL;DR: In this article, high-resolution transmission electron microscopy, electron diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectrograph, and elemental analysis were used to analyse the structural changes induced by annealing.
Abstract: High structural purity nanocrystalline SiC nanopowder can be produced in low pressure and low temperature radiofrequency (RF) plasmas by using silane and methane diluted in Ar. The main drawback is the low powder yield thus obtained. Powder yield can reach competitive levels by using pure silane and methane and increasing RF power. The as-formed powder shows local arrangement in silicon carbide units but it is highly hydrogenated and undergoes spontaneous oxidation when exposed to the atmosphere. In order to obtain both the high nucleation rate of SiC particles and the high structural purity, post-thermal treatments up to 1500 °C were performed on this as-formed SiC powder. Ex situ characterization techniques, such as high-resolution transmission electron microscopy, electron diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and elemental analysis, were used to analyse the structural changes induced by annealing.
15 Apr 2009
TL;DR: In this article, a particle collection apparatus is described, which includes a baghouse housing comprising an entrance port, a collection port, baghouse configured between the entrance port and the collection port and a vacuum port coupled to the baghouse.
Abstract: A particle collection apparatus is disclosed. The apparatus includes a baghouse housing comprising an entrance port, a collection port, a baghouse configured between the entrance port and the collection port, and a vacuum port coupled to the baghouse. The apparatus also includes a collection mechanism coupled to the collection port; and, a compression mechanism coupled to the baghouse.
TL;DR: In this article, a detailed survey of the polymerization processes in low-pressure plasmas used for industrial surface processing is surveyed, and the mechanism of macromolecule formation under low pressure conditions is discussed, and energetically favorable negative ion-assisted polymerization channels are proposed.
Abstract: Polymerization processes in low-pressure plasmas used for industrial surface processing are surveyed. Special attention is given to fluorocarbon plasmas, because of their importance in reactive ion etching of semiconductor elements. Diagnostic methods for the detection of large molecules are described, including mass spectrometry, infrared absorption and laser techniques. By means of a new mass spectrometric method, large amounts of polymeric species have been detected in radio-frequency fluorocarbon plasmas. Mechanisms of macromolecule formation under low-pressure conditions are discussed, and energetically favorable negative ion-assisted polymerization channels are proposed. Several fluorocarbon gases are studied: CF4, C2F6, C4F8 and C5F8. Polymerization efficiency increases with increasing size of the parent gas molecule, and with its decreasing fluorine to carbon ratio. Gas phase polymerization has important consequences for plasma chemistry and surface processing. It is strongly related to fluorocarbon film deposition on the surface. The presence of the film determines the etching performance of the plasma, introduces new surface reactions for radicals and positive ions, and can result in dust particle formation.
25 Jul 1999
TL;DR: In this article, the origin of photoluminescence emitted by silicon powder produced by plasma-enhanced chemical vapor deposition is analyzed in view of the structural changes induced by laser annealing.
Abstract: The origin of the photoluminescence (PL) emitted by silicon powder produced by plasma-enhanced chemical vapor deposition is analyzed in view of the structural changes induced by laser annealing. Both, the Raman spectra and the PL signal are qualitatively different before and after this process. It involves some degree of recrystallization which can be deduced from the Raman spectra and also from a strong emission of H2. The analysis shows that the characteristic PL does not come from the as-grown state of the sample but from the annealed state.