Nanoparticles from low-pressure, low-temperature plasmas
01 Jan 2000-pp 57-158
TL;DR: In this paper, the formation of particles in low-temperature, low-pressure plasmas is discussed and various technological aspects of the formation and characterization of the powders are discussed.
Abstract: Publisher Summary This chapter shows that low-pressure, low-temperature plasmas may generate a high particle nucleation rate and that they can allow for control of the composition, size, and atomic structure of the particles. These plasmas can produce nanometric particles of different composition, size, size distribution, and microstructure, depending on the discharge conditions. Besides the plasma parameters, modulation of the discharge and control of the duration of the plasma-on time can determine particle features. Results on the formation of powders of different alloys have also been presented. The scientific context of the formation of particles in low-temperature, low-pressure plasmas is reviewed. The basic studies of particles in interstellar space, the concern of the microelectronics industry about their contamination effect, the recent interest in nanostructured ceramics, and the new field of plasma crystals are also described. The various technological aspects of the formation and characterization of the powders are discussed. Detailed reports on the strong light emission observed in silicon nanoparticles produced in an rf discharge at low pressures showed that its origin is blackbody emission. In spite of using low laser intensities, nanoparticles heat up as a result of their low efficiency for dissipating heat through conduction between particles. This effect may be, in some cases, responsible for the light emission in other nanostructured materials.
Citations
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Patent•
13 Dec 2001TL;DR: In this article, a method for producing metallic nanoparticles is described. But the method is based on generating an aerosol of solid metallic microparticles, generating non-oxidizing plasma with a plasma hot zone at a temperature sufficiently high to vaporize the microparticle into metal vapor, and directing the aerosol into the hot zone of the plasma.
Abstract: Method for producing metallic nanoparticles. The method includes generating an aerosol of solid metallic microparticles, generating non-oxidizing plasma with a plasma hot zone at a temperature sufficiently high to vaporize the microparticles into metal vapor, and directing the aerosol into the hot zone of the plasma. The microparticles vaporize in the hot zone to metal vapor. The metal vapor is directed away from the hot zone and to the plasma afterglow where it cools and condenses to form solid metallic nanoparticles.
123 citations
Patent•
15 Jul 2002TL;DR: In this article, the authors proposed a method for producing metal oxide nanoparticles. But, the method requires an aerosol of solid metallic microparticles, generating a plasma with a plasma hot zone at a temperature sufficiently high to vaporize the micro-articles into metal vapor, and directing the aerosol into the hot zone of the plasma.
Abstract: Method for producing metal oxide nanoparticles. The method includes generating an aerosol of solid metallic microparticles, generating plasma with a plasma hot zone at a temperature sufficiently high to vaporize the microparticles into metal vapor, and directing the aerosol into the hot zone of the plasma. The microparticles vaporize in the hot zone into metal vapor. The metal vapor is directed away from the hot zone and into the cooler plasma afterglow where it oxidizes, cools and condenses to form solid metal oxide nanoparticles.
96 citations
TL;DR: In this article, a Si face-cubic-centered structure is demonstrated in nanocrystalline particles produced in low-pressure silane plasma at room temperature, and the existence of a well-defined crystalline structure different from the diamond-like structure of Si is discussed.
Abstract: Nanostructured Si thin films, also referred as polymorphous, were grown by plasma-enhanced chemical vapor deposition. The term “polymorphous” is used to define silicon material that consists of a two-phase mixture of amorphous and ordered Si. The plasma conditions were set to obtain Si thin films from the simultaneous deposition of radical and ordered nanoparticles. Here, a careful analysis by electron transmission microscopy and electron diffraction is reported with the aim to clarify the specific atomic structure of the nanocrystalline particles embedded in the films. Whatever the plasma conditions, the electron diffraction images always revealed the existence of a well-defined crystalline structure different from the diamondlike structure of Si. The formation of nanocrystallinelike films at low temperature is discussed. A Si face-cubic-centered structure is demonstrated here in nanocrystalline particles produced in low-pressure silane plasma at room temperature.
77 citations
TL;DR: An overview of the progress in the device physics and fabrications of the Si QD light-emitting diodes (LEDs) including new device structures to improve the light extraction efficiency as well as highlights in the growth of Si QDs and their quantum confinement effects (QCEs) is provided in this paper.
Abstract: An electrically driven light emitter from silicon is a long-standing problem in silicon photonics. Recently, significant progress has been made using silicon quantum dots (Si QDs) embedded in the silicon nitride thin films, transparent doping layers and electrodes, and surface-modified structures. This paper provides an overview of the progress in the device physics and fabrications of the Si QD light-emitting diodes (LEDs) including new device structures to improve the light extraction efficiency as well as highlights in the growth of the Si QDs and their quantum confinement effects (QCEs)
52 citations
Additional excerpts
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TL;DR: In this paper, the optical properties of silicon nanoparticles were measured in the mid-infrared region (2-20μm) and the resulting spectra show effects of light scattering as well as absorption features due to excitations of Si-O and Si-H bonds.
Abstract: The optical properties of silicon nanoparticles were measured in the mid-infrared region (2–20μm). The resulting spectra show effects of light scattering as well as absorption features due to excitations of Si–O and Si–H bonds. We are able to model the obtained spectra using an effective medium approach. The nanoparticles are best described using a Si–SiOx core-shell structure. We use the vibrational modes of the oxide to determine the thickness and the stoichiometry of the oxide. Using the Rayleigh scattering limit, we can describe the measured decrease in transmitted intensity. By fitting the theoretically modeled spectrum to the experimental data, we obtain the particle size and shape. Finally, we can identify the surface optical-phonon mode of SiOx, located between the transverse- and longitudinal-optical-phonon frequencies.
35 citations
References
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Book•
01 Jan 1983
TL;DR: In this paper, a Potpourri of Particles is used to describe surface modes in small Particles and the Angular Dependence of Scattering is shown to be a function of the size of the particles.
Abstract: BASIC THEORY. Electromagnetic Theory. Absorption and Scattering by an Arbitrary Particle. Absorption and Scattering by a Sphere. Particles Small Compared with the Wavelength. Rayleigh--Gans Theory. Geometrical Optics. A Potpourri of Particles. OPTICAL PROPERTIES OF BULK MATTER. Classical Theories of Optical Constants. Measured Optical Properties. OPTICAL PROPERTIES OF PARTICLES. Extinction. Surface Modes in Small Particles. Angular Dependence of Scattering. A Miscellany of Applications. Appendices. References. Index.
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TL;DR: Light scattering by small particles as mentioned in this paper, Light scattering by Small Particle Scattering (LPS), Light scattering with small particles (LSC), Light Scattering by Small Parts (LSP),
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TL;DR: Light scattering by small particles as mentioned in this paper, Light scattering by Small Particle Scattering (LPS), Light scattering with small particles (LSC), Light Scattering by Small Parts (LSP),
Abstract: Light scattering by small particles , Light scattering by small particles , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی
6,623 citations
TL;DR: In this paper, a new reversible photoelectronic effect was reported for amorphous Si produced by glow discharge of SiH4, where long exposure to light decreases both the photoconductivity and the dark conductivity.
Abstract: A new reversible photoelectronic effect is reported for amorphous Si produced by glow discharge of SiH4. Long exposure to light decreases both the photoconductivity and the dark conductivity, the latter by nearly four orders of magnitude. Annealing above 150 °C reverses the process. A model involving optically induced changes in gap states is proposed. The results have strong implications for both the physical nature of the material and for its applications in thin‐film solar cells, as well as the reproducibility of measurements on discharge‐produced Si.
2,673 citations
TL;DR: The processes that lead to charging of dust grains in a plasma are briefly reviewed in this article, where it is shown that the radial transport of dust contained in the spokes may be responsible for the rich radial structure in Saturn's rings.
Abstract: The processes that lead to charging of dust grains in a plasma are briefly reviewed. Whereas for single grains the results have been long known, the reduction of the average charge on a grain by 'Debye screening' has only recently been discovered. This reduction can be important in the Jovian ring and in the rings of Uranus. The emerging field of gravitoelectrodynamics which deals with the motion of charged grains in a planetary magnetosphere is then reviewed. Important mechanisms for distributing grains in radial distance are due to stochastic fluctuations of the grain charge and a systematic variation due to motion through plasma gradients. The electrostatic levitation model for the formation of spokes is discussed, and it is shown that the radial transport of dust contained in the spokes may be responsible for the rich radial structure in Saturn's rings. Finally, collective effects in dusty plasmas are discussed which affect various waves, such as density waves in planetary rings and low-frequency plasma waves. The possibility of charged grains forming a Coulomb lattice is briefly described.
1,470 citations