1,721,056 research outputs found
Crystalline and Non-crystalline Solids
No full textThe structural properties of materials play a fundamental role in the determination of their suitability for a specific application. This book is intended as a contribution to the efforts to increase the knowledge of the influence exerted on the properties of materials by their crystalline or amorphous structure. To this aim, some of the materials that are most promising for their use in different technological fields have been studied, namely graphene, titanium oxide, several types of functional metal oxides, porphyrinic crystalline solids, plasma deposited polymers, amorphous silicon, as well as hydrogenated amorphous carbon. These materials have been presented by the authors for their use in different applications, including microelectronics, photonics, and biomedicine
A Review of Experimental Investigations into the Time Evolution of Low-Pressure Capacitively Coupled Plasmas in Their Early Stages of Development
Full text linkCapacitively coupled plasma (CCP) discharges working at low pressure are widely used for the synthesis of thin films and the modification of the surface properties of materials. Due to their importance, considerable research was carried out over the years to understand their working mechanisms, and the physical properties of the CCP discharges were measured by many research groups, while simulations of their characteristics were often performed using both fluid and kinematic models. However, most of the simulation and characterization work found in the literature is focused on the discharge steady-state characteristics, since most of the applications rely on its properties, while less information is available on the early stages. In fact, the initial stages of CCP plasma discharges are of great importance to improve the understanding of their ignition process as well as to figure out the working mechanism of pulsed discharges, the use of which has increased in importance in recent years. In this work, a review of the results published in recent years concerning the physical mechanisms involved in the very first stages of low-pressure CCP discharges is presented, focusing on the first few microseconds of discharge time
Simulation of the first two microseconds of an Ar CCP cold plasma discharge by the PIC-MCC method
Full text linkMost simulations of capacitively coupled radiofrequency cold-plasma discharges (RF-CCP) are focused on the steady state, but the initial discharge time is important for understanding the ignition process and the behavior of pulsed discharges. In this work, the time evolution of an RF-CCP Ar discharge was simulated, considering a pressure of 66.6 Pa, a distance between the electrodes of 20 mm, and RF (13.56 MHz) bias amplitudes in range 100–400 V, and the discharge evolution was observed for the first 2 μs. A 1d3v (1 dimension for particle positions and 3 dimensions for particle velocities) electrostatic particle in cell with montecarlo collisions (PIC-MCC) model was used, with separated particle weights for electrons and ions that varied with the particle density. During the simulations, the time evolution of the electron density, mean electron energy, Debye length, Debye number, and plasma frequency were observed. The spatial distribution of electric potential and the electron energy distribution function were also monitored. A transition between two regimes was observed; the first was characterized by strong oscillation of the mean electron energy and an exponential increase of the mean plasma density with time, while in the second the mean electron energy was lower, and the plasma density increased linearly. The time required for the transition between the two regimes increased as the RF amplitude was raised from 100 to 250 V, then decreased with a further increase of the RF amplitude to 300 and 350 V
Silicon-carbon-oxynitrides grown by plasma-enhanced chemical vapor deposition technique
No full textIn this paper we report some preliminary results about the growth at low temperature (493 K) of hydrogenated silicon-carbon-oxygen- nitrogen amorphous thin-film alloys (a-SiCxOyNz:H) by means of capacitively-coupled radio-frequency (13.56 MHz) plasma-enhanced chemical vapor deposition using a mixtures of silane (SiH4), propane (C3H8), nitrous oxide (N2O) and ammonia (NH3) precursor gases. Thin films of a- SiCxOyNz:H were grown at different deposition conditions, obtaining growth speeds varying from 0.22 to 0.44 nm/s. The films were characterized by means of Fourier transform infra-red spectroscopy in order to investigate the internal bonding structure, by UV-VIS transmittance spectroscopy to check the optical properties and by mechanical profilometry to measure the film thickness and estimate the growth rate. The comparison of structural and optical properties of samples grown with and without NH3 presence in the gas mixture showed that the ammonia addition allows a better control of nitrogen incorporation in the film structure, while increasing film transparency and reducing the growth rate
Study of the interaction between the surface of polymeric substrates and chromium thin coatings grown by RF and DC sputtering
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Promising Antimicrobial Properties of Silicon-Based Thin-Film Coatings
No full textSilicon-based thin films, such as silicon and silicon-based alloys, have been intensively studied, especially for their use in microelectronics and large area electronics. However, they also show interesting properties regarding their biological interaction, although these characteristics have been studied to a lower extent. Recently, promising antibacterial properties of some silicon-based materials have been investigated, showing their potential ability to reduce the adhesion of some types of bacteria on the surfaces onto which they are applied. Since these properties rely on the reduction of bacterial adhesion, instead of exploiting the release of antibacterial agents such as Ag ions or nanoparticles, they show the advantage of preventing potentially harmful long-time effects that could be exerted by these agents in the host tissues. Moreover, this approach avoids the risk that the release intensity of these agents is reduced over time due to their depletion inside the material. Due to the wide range of interesting properties of silicon-based materials, including biocompatibility increase, barrier action against the release of chemicals, and tuning of surface energy, the production of multifunctional coatings could also be possible. In this chapter, the most important properties of silicon-based thin films are reviewed, and some results concerning the potential antibacterial properties of silicon-oxygen amorphous thin-film alloys (a-SiOx) are presented in detail
Physical properties of ECR-CVD polycrystalline SiC films for Micro-Electro-Mechanical-Systems
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