Josep Costa

Bio: Josep Costa is an academic researcher. The author has contributed to research in topics: Particle & Nanoparticle. The author has an hindex of 1, co-authored 1 publications receiving 11 citations.

Nanoparticles from low-pressure, low-temperature plasmas

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.

Method for producing metallic nanoparticles

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.

Method for producing metal oxide nanoparticles

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.

Atomic structure of the nanocrystalline Si particles appearing in nanostructured Si thin films produced in low-temperature radiofrequency plasmas

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.

Physics and Device Structures of Highly Efficient Silicon Quantum Dots Based Silicon Nitride Light-Emitting Diodes

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)

Infrared properties of silicon nanoparticles

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.