Effects of plasma processing on the microstructural properties of silicon powders
TL;DR: In this article, the effects of plasma processing conditions on the microstructural properties of silicon powders are presented, which reveal an increase in hydrogen content and a reduction in volume/surface ratio as the modulation frequency of RF power increases.
Abstract: The effects of plasma processing conditions on the microstructural properties of silicon powders are presented. Hydrogenated nanophase silicon powders were prepared using low-pressure and low-temperature square wave modulated RF plasma (13.56 MHz) using pure silane gas. Plasma parameters such as pressure, RF power, plasma modulation frequency, and gas flow rate were varied. In situ analysis by quadrupolar mass spectroscopy and ex situ analysis of the silicon powders by Fourier transform infrared spectroscopy (FTIR) and thermal desorption spectrometry of hydrogen were performed. The thermal desorption spectrometry results show the fundamental differences between the concentrations of hydrogen weakly and strongly bonded in silicon powders as compared to amorphous silicon films. The FTIR analysis also determined the microstructural characteristics of powders and hence their volume/surface ratio. This parameter was determined from the balance of Pj probabilities of having one of the Hj-Si-Si4-j bond arrangements in the powder particles. These results reveal an increase in hydrogen content and a reduction in volume/surface ratio as the modulation frequency of RF power increases. In consequence, higher compactness of silicon powders is associated with long particle residence times inside the plasma as a result of ion bombardment. TEM analysis indicated a considerable dispersion of particle size and some degree of structure of the silicon powder characterized by intergrain linkage. We point out the dominant presence of hydrogen on the particle surfaces (external voids), which may cause the high reactivity of grains, increasing the degree of intergrain linkage.
Citations
More filters
TL;DR: An overview of dynamic self-organization phenomena in complex ionized gas systems, associated physical phenomena, and industrial applications is presented in this paper, where the most recent experimental, theoretical, and modeling efforts to understand the growth mechanisms and dynamics of nano- and micron-sized particles, as well as the unique properties of the plasma-particle systems (colloidal, or complex plasmas) and the associated physical effects are reviewed and the major technological applications of micro- and nanoparticles are discussed.
322 citations
Patent•
17 Jun 2005TL;DR: In this paper, a method for the synthesis of single-crystal semiconductor nanoparticles, including photoluminescent silicon nanoparticles with diameters of no more than 10 nm, is described.
Abstract: Methods and apparatus for producing nanoparticles, including single-crystal semiconductor nanoparticles, are provided. The methods include the step of generating a constricted radiofrequency plasma in the presence of a precursor gas containing precursor molecules to form nanoparticles. Single-crystal semiconductor nanoparticles, including photoluminescent silicon nanoparticles, having diameters of no more than 10 nm may be fabricated in accordance with the methods.
191 citations
TL;DR: In this article, the effect of water vapour plasma treatment on the shrinkage behavior and chemical properties of the surface of keratin fibres was studied, and it was shown that the wettability and shrink resistance of wool were improved even at low plasma treatment times.
Abstract: The effect of water vapour plasma treatment on the shrinkage behaviour and chemical properties of the surface of keratin fibres was studied. The wettability and shrink resistance of wool were improved even at low plasma treatment times. The values of the advancing contact angles of keratin fibres treated with plasma provide evidence of the formation of hydrophilic groups in the wool surface. Analysis by XPS reveals that oxidation of the fatty acid monolayer (F-layer) prevails over its removal in the early stages of plasma treatment. The increase in treatment time results in a progressive removal of the F-layer. Copyright © 2003 John Wiley & Sons, Ltd.
76 citations
TL;DR: In this paper, experimental results were presented demonstrating particle production in an argon discharge, using a variety of target materials, including graphite, titanium, tungsten, and stainless steel.
Abstract: Submicron to micron size particles are produced in the gas phase of sputtering discharges These particles can contaminate thin films grown by sputter deposition On the other hand, particle production in a discharge can be desirable when used for manufacturing fine powders Here, experimental results are presented demonstrating particle production in an argon discharge, using a variety of target materials The rate of particle growth varied widely, depending on the target material Particles grown to 300 nm–5 μm, usually have one of two different shapes Compact particles with a nearly spherical shape were produced by sputtering graphite, titanium, tungsten, and stainless steel targets, while filamentary-shaped fractal particles formed when sputtering aluminum and copper targets Particle growth was also observed for a target made of an insulating material
75 citations
TL;DR: In this paper, the influence of the gas type, air or nitrogen, and the treatment time in an RF glow discharge treatment on the shrink resistance properties of knitted wool fabric and wetting properties of keratin fibres were studied.
Abstract: The influence of the gas type, air or nitrogen, and the treatment time in an RF glow discharge treatment on the shrink resistance properties of knitted wool fabric and wetting properties of keratin fibres were studied. Wetting properties were determined by means of contact angle measurements on single keratin fibres. This method allows measuring accurately the influence of the plasma gas type and treatment time on fibre hydrophilicity, and its modification with the time elapsed after plasma treatment. The modification of the surface properties should be taken into account, especially, when a biopolymer after-treatment is applied to achieve wool shrink resistance. Surface chemical changes were studied by means of XPS. Topographical changes in the wool fibre surface were observed by scanning electron microscopy (SEM) and surface damage was evaluated by means of the Herbig sac formation. Both air and nitrogen plasma treatments impart shrink resistance to wool fabric and hydrophilic properties to the keratin ...
61 citations
References
More filters
TL;DR: In this article, the connection between microstructure and absolute limits to the allowed values of the dielectric response of two-phase composites is reviewed and a solution of the Clausius-Mossotti problem is developed from basic principles.
1,433 citations
TL;DR: This paper has modeled the shape of the SiH bond-stretching band as a function of the alloy composition, and finds that the frequency shifts caused by changes in the matrix are comparable to the shifts associated with the different local environments.
Abstract: Hydrogenated silicon suboxides, ${\mathrm{SiO}}_{\mathrm{r}}$:H, for alloy range (0lrl2) have been deposited by remote plasma-enhanced chemical vapor deposition (remote PECVD) under conditions in which hydrogen is incorporated predominantly in monohydride or SiH bonding configurations. We have investigated both the SiH bond-stretching and bond-bending absorption bands by infrared (ir) absorption spectroscopy as a function of r, the alloy composition. In this paper, we have focused on the bond-stretching absorption bands, and have modeled the shape of the bond-stretching band as a function of the alloy composition. There are four distinct local environments for the SiH group in the sub- oxides; these can be written as HSi-${\mathrm{Si}}_{3\mathrm{\ensuremath{-}}\mathrm{n}}$${\mathrm{O}}_{\mathrm{n}}$, for n=0--3. A sum of Gaussian functions, one for each environment, is used to synthesize the absorption in the SiH stretching band. The peak positions of these Gaussians are calculated by an induction model which includes both local and matrix (or alloy) effects; the amplitude weightings are determined from a random statistical model for the local bonding environments of the Si-O groups in the ${\mathrm{SiO}}_{\mathrm{r}}$ alloy. We find that the frequency shifts caused by changes in the matrix, and associated with different values of r, are comparable to the shifts associated with the different local environments. The combination of these effects serves to diminish the discreteness of subband features in the absorption spectrum.
383 citations
TL;DR: The doublet structure of the infrared absorption in the silicon-hydrogen stretch region for amorphous silicon is attributed mainly to environmental effects rather than to different SiH x (x = 1,2,3) groups.
167 citations
TL;DR: In this paper, the time evolution of the size of particles produced in a silane-argon low pressure radiofrequency discharge has been determined in the nanometer to the micrometer range using transmission electron microscopy.
Abstract: The time evolution of the size of particles produced in a silane‐argon low‐pressure radio‐frequency discharge has been determined in the nanometer to the micrometer range using transmission electron microscopy Highly ‘‘monodisperse’’ distributions are observed and their temporal evolution is followed These studies are combined with laser light scattering measurements to obtain particle densities, which are of the order of 107 cm−3 For short plasma durations (Δt<5 s), a fast (10 nm/s) linear increase in diameter is measured
165 citations
TL;DR: In this paper, a simple particle-scavenging arrangement based on thermophoresis was proposed to remove particles from glow discharges, where the particles are suspended in the discharge and move away from a heated electrode towards a cooled electrode.
Abstract: Particles in glow discharges are charged negatively and are therefore often suspended electrostatically since the plasma potential is usually more positive than the potential of surfaces bounding the plasma. However, in addition to responding to electrostatic and gravitational forces, particles are sensitive to forces associated with gradients in neutral gas temperature. A series of experiments were performed varying the temperature of water circulated through planar, parallel electrodes. When particles are present and are suspended in the discharge, they move away from a heated electrode and towards a cooled electrode. In the absence of particles, the discharge optical emission spatial profile and electrical characteristics did not change significantly for any combination of electrode heating or cooling. Particles remaining in the interelectrode gap after the discharge is extinguished appear to be uncharged. With particles present, the discharge electrical properties and time‐ and space‐resolved optical emission take on characteristics associated with discharges in electron attaching gases. We report on a simple particle‐scavenging arrangement based on thermophoresis that can be used to remove particles from a discharge.
162 citations