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 paper, the authors reported the production of SiN nanopowder at room temperature and low pressure by RF glow discharge decomposition of SiH 4 and NH 3 gases, where the RF power was modulated at 0.5 Hz with a duty cycle of 20% in order to control the size of the expelled particles.
Abstract: Square-wave modulated radio frequency (RF) plasmas have been shown to be a suitable source of nanometric size powder with high purity and controllable nanostructure. This paper reports the production of SiN nanopowder at room temperature and low pressure by RF glow discharge decomposition of SiH 4 and NH 3 gases. The RF power was modulated at 0.5 Hz with a duty cycle of 20% in order to control the size of the expelled particles. A study of the particle formation process using in-situ monitoring of the RF dissipated power is presented. Transmission electron microscopy showed a narrow size distribution of spherical particles from 25 to 45 nm and their electron diffraction provided evidence of a short range order in Si or SiN units depending on the precursor gas mixture. Analysis by Fourier transform infrared spectroscopy revealed the presence of SiN, NH and SiH bonds and the elemental analysis of the powder determined its chemical composition.
TL;DR: In this article, a nanometric powder of silicon carbide has been produced in a radiofrequency square wave-modulated glow discharge of SiH 4 and CH 4 gases, and the chemical composition of the powder was determined by X-ray photoelectron spectroscopy.
Abstract: Nanometric powder of silicon carbide has been produced in a radiofrequency square wave-modulated glow discharge of SiH 4 and CH 4 gases. The transient behavior observed in the power absorbed during the discharge has been related to the various steps of the formation of particles. At the transmission electron microscope, two populations of particles were found: around 70 and 300nm. Electron diffraction patterns showed that the particles were amorphous although the short-range order was similar to that of β-SiC micrometric powder. The atomic concentrations of Si, C and H were determined by elemental analysis. The chemical composition was determined by X-ray photoelectron spectroscopy. The polymeric character of the powder was evident from the presence of CH 2 and CH 3 species as indicated by RAMAN and FTIR spectroscopies.
TL;DR: In this paper, carbon nanotubes (CNTs) were in situ reacted with tetramethysilane (TMS) in a chemical vapor deposition (CVD) reactor.
Abstract: Silicon carbide (SiC) micro-crystals were grown on an Si(100) substrate by the reaction of carbon nanotubes (CNTs) with tetramethysilane (TMS) in a chemical vapor deposition (CVD) reactor. CNTs were catalytically grown on an Si(100) substrate by the thermal cracking of acetylene. The grown CNTs were in situ reacted with TMS in the CVD reactor. Micro-sized SiC crystals were uniformly grown across the Si substrate. The growth of the SiC micro-crystals was characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Raman and photoluminescence (PL) spectroscopy. Higher temperature and longer time were favorable for the growth of good quality SiC micro-crystals. The blue shift of the PL spectra was observed from the SiC micro-crystals. The growth mechanism of micro-sized SiC crystals is discussed.
TL;DR: In this article, the effects of the synthesis conditions on the size and morphology of silicon dioxide particles prepared in a plasma field were investigated systematically, and it was shown that an increase in the rf power not only accelerated the plasma reaction but also enhanced the formation of agglomerated particles.
Abstract: The effects of the synthesis conditions on the size and morphology of silicon dioxide particles prepared in a plasma field were investigated systematically. In this study, silicon dioxide particles were synthesized by a plasma reaction of a mixture of tetraethylorthosilicate and oxygen in a coaxial-type nonequilibrium plasma reactor. Since particles suspended in a nonequilibrium plasma field are known to be charged unipolarly (negatively), the generation of agglomerated particles is expected to be suppressed. An increase in the rf power not only accelerated the plasma reaction, but also enhanced the formation of agglomerated particles. This is considered to be caused by the generation of smaller primary particles with increasing rf power, which led to insufficient particle charging in the plasma. The diameter of the synthesized particles decreased with decreasing residence time. In this case, nonagglomerated particles with a size of less than 10 nm could be produced, in contrast to those in the case of increased rf power. The effects of the precursor concentration on the particle characteristics were also examined. An increase in the precursor concentration resulted in smaller primary particles. In this case, the coagulation between small, and thus insufficiently charged, primary particles were considered to be predominant. Under selected operating conditions, nonagglomerated particles with a diameter of up to 50 nm could be prepared.
TL;DR: In this paper, a detailed study is reported concerning the oxidation of SiC nanoparticles obtained by plasma-enhanced chemical-vapour deposition (PECVD) using thermogravimetry, infrared spectroscopy and elementary analysis.
Abstract: A detailed study is reported concerning oxidation of SiC nanoparticles obtained by plasma-enhanced chemical-vapour deposition (PECVD). The oxidation process has been analysed by thermogravimetry, infrared spectroscopy and elementary analysis. The oxidation behaviour of the as-grown powder can be understood in view of its polymeric structure containing a large amount of hydrogen that allows rapid diffusion of oxygen. Two steps have been identified: first, oxygen is incorporated as the bridging atom between two silicon atoms; and second, methyl groups are lost giving to a progressive restructuration of Si–O bonds to form silica. While the first step involves a mass gain, the second step results in a significant mass loss. After a heat treatment at 900°C of the as-grown sample, no hydrogen remains and the excess carbon precipitates, leading to a more dense packing of Si and C atoms that avoids diffusion of oxygen into the volume. In this case, oxidation is much slower because a protective layer of SiO 2 is formed.
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.