Role of low-energy electrons in Ar emission from low-pressure radio frequency discharge plasma

Optical emission spectra from a low-pressure Ar plasma were studied with high spatial resolution. It has been shown that the intensity ratios of Ar lines excited through metastable levels to those excited directly from the ground state are sensitive to the shape of electron energy distribution function. From these measurements, important information on the spatial variation of plasma parameters can be obtained. (C) 1999 American Institute of Physics. [S0003-6951(99)01629-0].

Structure observed in measured electron energy distribution functions in capacitively coupled radio frequency hydrogen plasmas

Electron energy probability functions measured with a passively compensated Langmuir probe in asymmetric capacitively coupled hydrogen and deuterium plasmas exhibit structure. The otherwise relatively continuous distribution appears to have an abrupt peak in electron density near 5 eV. This structure occurs at a higher energy in deuterium than hydrogen and there is a correlation between floating potential and the voltage at which the structure is observed in the second derivative of the I(V) characteristic. While the cause of the structure has yet to be clarified, spectroscopic observations and computer-based hydrogen models indicate that the high energy tail of the distribution is strongly modulated during the radio frequency cycle. The effect of this modulation on plasma properties and probe measurements has yet to be explored. (C) 1999 American Institute of Physics. [S0003-6951(99)00819-0].

Design of a radio frequency heated isothermal micro-trickle bed reactor

A near-isothermal micro-trickle bed reactor operated under radio frequency heating was developed. The reactor bed was packed with nickel ferrite micro-particles of 110. μm diameter, generating heat by the application of RF field at 180. kHz. Hydrodynamics in a co-current configuration was analysed and heat transfer rates were determined at temperature ranging from 55 to 100. °C. A multi-zone reactor bed of several heating and catalytic zones was proposed in order to achieve near-isothermal operations. Exact positioning, number of the heating zones and length of the heating zones composed of a mixture of nickel ferrite and a catalyst were determined by solving a one dimensional model of heat transfer by conduction and convection. The conductive losses contributed up to 30% in the total thermal losses from the reactor. Three heating zones were required to obtain an isothermal length of 50. mm with a temperature non-uniformity of 2. K. A good agreement between the modelling and experimental results was obtained for temperature profiles of the reactor. © 2013 Elsevier B.V.

Electron dynamics and frequency coupling in a radio-frequency capacitively biased planar coil inductively coupled plasma system

The electron dynamics in a planar coil inductively coupled plasma (ICP) system with a capacitively biased electrode is investigated using space and phase resolved optical emission spectroscopy. The two power source frequencies are exact multiple of each other and phase-locked. In this configuration, the system is investigated when the coil is operated in both E-mode and H-mode. The results show that in a phase synchronized RF biased ICP, the electrode bias power couples with the capacitive contribution of the coil, in both E-mode and H-modes, similar to dual-frequency capacitively coupled plasmas (2f-CCPs). It is also demonstrated that in H-mode, the phase between the electrode bias frequency and the ICP coil frequency influences the electron heating, similar to the electrical asymmetry effect in 2f-CCPs.

Q-enhancement with on-chip inductor optimization for reconfigurable Δ-Σ radio-frequency ADC

The paper details on-chip inductor optimization for a reconfigurable continuous-time delta-sigma (Δ-Σ) modulator based radio-frequency analog-to-digital converter. Inductor optimisation enables the Δ-Σ modulator with Q enhanced LC tank circuits employing a single high Q-factor on-chip inductor and lesser quantizer levels thereby reducing the circuit complexity for excess loop delay, power dissipation and dynamic element matching. System level simulations indicate at a Q-factor of 75 Δ- Σ modulator with a 3-level quantizer achieves dynamic ranges of 106, 82 dB and 84 dB for RFID, TETRA, and Galileo over bandwidths of 200 kHz, 10 MHz and 40 MHz respectively.

Radio Frequency Synthesis for Power-Constrained Systems

Thesis (Ph.D.)--University of Washington, 2015

Growth and Characterisation of Radio Frequency Magnetron Sputttered Indium Tin Oxide Thin Films

The increasing interest in the interaction of light with electricity and electronically active materials made the materials and techniques for producing semitransparent electrically conducting films particularly attractive. Transparent conductors have found major applications in a number of electronic and optoelectronic devices including resistors, transparent heating elements, antistatic and electromagnetic shield coatings, transparent electrode for solar cells, antireflection coatings, heat reflecting mirrors in glass windows and many other. Tin doped indium oxide (indium tin oxide or ITO) is one of the most commonly used transparent conducting oxides. At present and likely well into the future this material offers best available performance in terms of conductivity and transmittivity combined with excellent environmental stability, reproducibility and good surface morphology. Although partial transparency, with a reduction in conductivity, can be obtained for very thin metallic films, high transparency and simultaneously high conductivity cannot be attained in intrinsic stoichiometric materials. The only way this can be achieved is by creating electron degeneracy in a wide bandgap (Eg > 3eV or more for visible radiation) material by controllably introducing non-stoichiometry and/or appropriate dopants. These conditions can be conveniently met for ITO as well as a number of other materials like Zinc oxide, Cadmium oxide etc. ITO shows interesting and technologically important combination of properties viz high luminous transmittance, high IR reflectance, good electrical conductivity, excellent substrate adherence and chemical inertness. ITO is a key part of solar cells, window coatings, energy efficient buildings, and flat panel displays. In solar cells, ITO can be the transparent, conducting top layer that lets light into the cell to shine the junction and lets electricity flow out. Improving the ITO layer can help improve the solar cell efficiency. A transparent ii conducting oxide is a material with high transparency in a derived part of the spectrum and high electrical conductivity. Beyond these key properties of transparent conducting oxides (TCOs), ITO has a number of other key characteristics. The structure of ITO can be amorphous, crystalline, or mixed, depending on the deposition temperature and atmosphere. The electro-optical properties are a function of the crystallinity of the material. In general, ITO deposited at room temperature is amorphous, and ITO deposited at higher temperatures is crystalline. Depositing at high temperatures is more expensive than at room temperature, and this method may not be compatible with the underlying devices. The main objective of this thesis work is to optimise the growth conditions of Indium tin oxide thin films at low processing temperatures. The films are prepared by radio frequency magnetron sputtering under various deposition conditions. The films are also deposited on to flexible substrates by employing bias sputtering technique. The films thus grown were characterised using different tools. A powder x-ray diffractometer was used to analyse the crystalline nature of the films. The energy dispersive x-ray analysis (EDX) and scanning electron microscopy (SEM) were used for evaluating the composition and morphology of the films. Optical properties were investigated using the UVVIS- NIR spectrophotometer by recording the transmission/absorption spectra. The electrical properties were studied using vander Pauw four probe technique. The plasma generated during the sputtering of the ITO target was analysed using Langmuir probe and optical emission spectral studies.

Characterization of radio frequency plasma using Langmuir probe and optical emission spectroscopy

The radio frequency plasma generated during the sputtering of Indium Tin Oxide target using Argon was analyzed by Langmuir probe and optical-emission spectroscopy. The basic plasma parameters such as electron temperature and ion density were evaluated. These studies were carried out by varying the RF power from 20 to 50 W. A linear increase in ion density and an exponential decrease in electron temperature with rf power were observed. The measured plasma parameters were then correlated with the properties of ITO thin films deposited under similar plasma conditions.

Determination of charge carrier transport in radio frequency plasma polymerized aniline thin films

The carrier transport mechanism of polyaniline (PA) thin films prepared by radio frequency plasma polymerization is described in this paper. The mechanism of electrical conduction and carrier mobility of PA thin films for different temperatures were examined using the aluminium–PA–aluminium (Al–PA–Al) structure. It is found that the mechanism of carrier transport in these thin films is space charge limited conduction. J –V studies on an asymmetric electrode configuration using indium tin oxide (ITO) as the base electrode and Al as the upper electrode (ITO–PA–Al structure) show a diode-like behaviour with a considerable rectification ratio

Radio frequency energy harvesting in wireless sensor networks

As a vital factor affecting system cost and lifetime, energy consumption in wireless sensor networks (WSNs) has been paid much attention to. This article presents a new approach to making use of electromagnetic energy from useless radio frequency (RF) signals transmitted in WSNs, with a quantitative analysis showing its feasibility. A mechanism to harvest the energy either passively or actively is proposed.

Tensile strength of radio frequency cold plasma treated PET fibers - Part 1: Influence of environment and treatment time

This article reports on a series of experiments with polyethylene terepthalate (PET) treated in a radio frequency plasma reactor using argon and oxygen as a gas fuel, for treatment times equal to 5 s, 20 s, 30 s, and 100 s. The mechanical strength modification of PET fibers, evaluated by tensile tests on monofilaments, showed that oxygen and argon plasma treatment resulted in a decrease in the average tensile strength compared with the untreated fibers. This reduction in tensile strength is more significant for argon plasma and is very sensitive to the treatment time for oxygen plasma. Scanning electron microscopy (SEM) used to analyze the effects of cold plasma treatment on fiber surfaces indicates differences in roughness profiles depending on the type of treatments, which were associated with variations in mechanical strength. Differences in the roughness profile, surveyed through an image analysis method, provided the distance of roughness interval, D-ri. This parameter represents the number of peaks contained in a unit length and was introduced to correlate fiber surface condition, before and after cold plasma treatments, and average tensile strength. Statistical analysis of experimental data, using Weibull cumulative distribution and linear representation, was performed to explain influences of treatment time and environmental effects on mechanical properties. The shape parameter, alpha, and density parameter, beta, from the Weibull distribution function were used to indicate the experimental data range and to confirm the mechanical performance obtained experimentally.

Effects of thermal annealing on the semi-insulating properties of radio frequency magnetron sputtering-produced germanate thin films

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)