Radio Frequency Inductively Coupled Plasma Research Articles

Controllable wettability of poly(ethylene terephthlate) film modified by oxygen combined inductively and capacitively coupled radio-frequency plasma

Poly(ethylene terephthalate) (PET) film was modified by using oxygen combined inductively coupled radio-frequency plasma (ICP) and capacitively coupled radio-frequency plasma (CCP) at the radio-frequency (RF) power of 200 W and 100 W, respectively, for a treatment time up to 300 s. The RF plasma modification under the combined ICP and CCP mode with the controllable oxygen plasma density and oxygen ion-flux energy significantly improved the wettability of PET film, due to the creation of the polar functional groups containing oxygen, such as C–O and O–C O, and the increase of the surface roughness. At a low surface roughness, the polar functional groups on the PET film affected both the advancing contact angles and receding contact angles. When the surface roughness increased over a threshold, the advancing contact angles mainly depended on the polar functional groups, and the receding contact angles were particularly dependent on the surface roughness. Therefore, the controllable advancing contact angles and receding contact angles on the plasma-modified PET film were independently determined by plasma functionalization and plasma etching under the combined ICP and CCP mode.

Hydrophobic and Hydrophilic Surface Nano-Modification of PET Fabric by Plasma Process

Polyethylene terephthalate (PET) fabrics were treated by radio frequency inductively coupled plasma (RF-ICP) to modify their hydrophobic and hydrophilic properties. Types of gases which were SF6, O2, N2 and Ar, treatment time, pressure and RF power were varied systematically. The water droplet contact angle measurements showed that, treating with SF6 plasma would result in the increase of hydrophobicity of PET samples while treating with O2, N2 and Ar plasmas would yield hydrophilic properties. In both hydrophobic and hydrophilic cases, the surface morphology of PET fibers was roughened after exposed to plasma. Hence, it is not obvious that these surface roughness induced by plasma is sufficient to yield the increase in hydrophobicity by the well known lotus effect.

State-space modeling of the radio frequency inductively-coupled plasma generator

Computational fluid dynamics models of RF-ICP are useful in understanding the basic transport phenomenon in an ICP torch under a wide variety of operating conditions. However, these models lack the ability to evaluate the effects of the plasma condition on the RF generator. In this paper, simulation of an induction plasma generator has been done using state space modelling by considering inductively coupled plasma as a part of RF network .The time dependent response of the RF-ICP generator circuit to given input excitation has been computed by extracting the circuit's state-space variables and their constraint matrices. MATLAB 7.1 software has been used to solve the state equations. The values of RF coil current, frequency and plasma power has been measured experimentally also at different plate bias voltage. The simulated model is able to predict RF coil current, frequency, plasma power, overall efficiency of the generator. The simulated and measured values are in agreement with each other. This model can prove useful as a design tool for the Induction plasma generator.

Improvement of Hydrophobic Properties of the Electrospun PVA Fabrics by SF<sub>6</sub> Plasma Treatment

Electrospun fabrics, prepared from 5, 7 and 10%w/v were Poly(vinyl alcohol) (PVA) solutions successfully prepared. The electrospinning condition was 15 kV, distance 15 cm, flow rate of 1 ml/hr and spinning time of 5 hours. Physical properties of electrospun PVA fabrics were analysed by SEM, FE-SEM and contact angle measurement.The contact angle of the electrospun PVA fabrics was 54.5°, characterizing the hydrophilicity of the fabrics. Hydrophobic properties of the electrospun PVA fabrics were improved by plasma treatment using radio frequency inductively coupled plasma (RF-ICP). RF-ICP plasma treatment of the electrospun PVA fabrics were carried out sulphurhexafluorene (SF6) gas with pressure of 0.5 Torr, RF power of 30W and treating time of 30, 60, 90 and 120 seconds. Effects of the PVA solution concentration and plasma treating time on hydrophobicity of the electrospun PVA fabrics were determined by contact angle that result of contact angle of treated fabrics increased when treated time increased and they decreased when concentration of fabrics increased.

Measurement of Surface Tension, Viscosity, and Density at High Temperatures by Free-Fall Drop Oscillation

The measurements of surface tension, viscosity, and density of metallic samples are described in this article. Samples are brought to their melting point by exposure to a radio-frequency–inductively coupled plasma (RF-ICP) torch. The measurements are based on oscillations in free-falling drops and the damping rate of the oscillations. The results of the measurements performed on copper and nickel samples showed a reasonable agreement with values calculated by other methods, such as drop-weight, pendant-drop, and drop-profile methods. According to the characteristics of this method, analysis of very high-temperature materials, such as refractories and ceramics, is possible.

Electron release in the afterglow of a pulsed inductively-coupled radiofrequency oxygen plasma

A pulsed inductively-coupled radiofrequency plasma in oxygen is investigated by means of time-resolved microwave interferometry in a wide pressure range from 0.5 to 200 Pa. In the afterglow a peak of the electron density is observed. The effect is maximum for pressures around 50 Pa. The time-resolved measurements of the electron density are interpreted in the framework of a fluid model. This model points out the significance of negative ions. The overall electron density is comparatively small. Attachment and detachment processes nearly balance during the power-on phase. But when the power is switched off, the electron temperature drops very quickly. This means that the production of new negative ions is inhibited so that the negative ions are destroyed by collisions. These reactions quickly set free electrons in the afterglow and are the reason for the observed peak in the electron density after switching off the power.

Synthesis of c-BN films by using a low-pressure inductively coupled BF 3–He–N 2–H 2 plasma

Cubic boron nitride (c-BN) films were synthesized by low-pressure inductively coupled radio-frequency plasma (ICP) chemical vapor deposition (CVD) from a gas mixture of borontrifluoride (BF 3), nitrogen, hydrogen and helium. BN films containing 50–80% cubic phase were obtained under 100 mTorr and at 750–1050 °C of substrate temperature. Substrate bias voltage required to obtain c-BN decreased down to − 20 V with increasing substrate temperature. The adhesion was also improved at high substrate temperatures as compared with those obtained in the B 2H 6–Ar–N 2–H 2 gas system, probably because of the decrease of bombarding energy and chemical effects of fluorine for selective deposition of c-BN.

Enhancement of c-axis texture of AlN films by substrate implantation

Highly oriented AlN films are successfully deposited on B+ implanted Si(111) substrates in a radio frequency inductively coupled plasma (RF/ICP) system. The implanted energy and dose used for the B+ implanted Si(111) substrates are 200keV and 1015cm−2, respectively. The c-axis texture of AlN films can be affected by RF gun power and ion implantation. Experimental results show that the full width at half-maximum (FWHM) of AlN(002) in the X-ray rocking curve measurements decreases with increasing RF gun power. The optimum condition is at 500W, where the FWHM of the AlN films deposited on Si(111) with and without B+ implantation are 2.77 and 3.17, respectively. In average, the FWHM of the AlN films on B+ implanted Si(111) are less than those on Si(111) by a factor of ∼10%. The enhancement of c-axis of AlN films due to B+ implantation is attributed to the reduction of AlN grains. Raman spectra also suggest that ion implantation plays a role in reducing the tensile stress in AlN films deposited on B+ implanted Si(111).

Numerical Analysis of Metallic Nanoparticle Synthesis Using RF Inductively Coupled Plasma Flows

A thermal plasma flow is regarded as a multifunctional fluid with high energy density, high chemical reactivity, variable properties, and controllability by electromagnetic fields. Especially a radio frequency inductively coupled plasma (RF-ICP) flow has a large plasma volume, long chemical reaction time, and a high quenching rate. Besides, it is inherently clean because it is produced without internal electrodes. An RF-ICP flow is, therefore, considered to be very useful for nanoparticle synthesis. However, nanoparticle synthesis using an RF-ICP flow includes complicated phenomena with field interactions. In the present study, numerical analysis was conducted to investigate the synthesis of metallic nanoparticles using an advanced RF-ICP reactor. An advanced RF-ICP flow is generated by adding direct current (DC) discharge to a conventional RF-ICP flow in order to overcome the disadvantages of a conventional one. The objectives of the present work are to clarify the formation mechanism of metallic nanoparticles in advanced RF-ICP flow systems and to detect effective factors on required synthesis. A two-dimensional model as well as a one-dimensional model was introduced for nanoparticle growth to investigate effects of spatial distributions of thermofluid fields in RF-ICP flows on synthesized nanoparticles. In an advanced RF-ICP flow, a characteristic recirculation zone disappears due to a DC plasma jet. Larger numbers of nanoparticles with smaller size are produced by using an advanced RF-ICP flow. Thermofluid fields in RF-ICP flows can be controlled by applied coil frequency by means of skin effect. Larger numbers of nanoparticles with smaller size are produced near the central axis. Dispersion of particle size distributions can be suppressed by higher applied coil frequency through control of RF-ICP flows. Applied coil frequency can be a remarkably effective factor to control nanoparticle size distribution.

High temperature surface tension measurement

Atmospheric radio frequency inductively coupled plasma (RF-ICP) is used as the high temperature heat source in this containerless method to measure the surface tension and viscosity of high melting point materials. Dynamics of melting, droplet formation, and drop detachment of a rod exposed to RF plasma are recorded. Using a three-dimensional model in which flow field, heat transfer, and phase change are solved, the melting process of the rod will be simulated. Comparing simulations and experiments, surface tension, and viscosity of ceramics can be obtained. Some preliminary results from the experiments for copper and alumina are reported in the present study.

Three-dimensional remarkable images of low-pressure H/sub 2/ ICP in E-mode

Computerized tomography (CT), in association with optical emission spectroscopy (OES), is used to investigate the three-dimensional image of radio frequency inductively coupled plasma (RF-ICP) in low-pressure hydrogen in E-mode. As a series of CT studies in this paper, we demonstrate a distinct image in H/sub 2/ ICP in the E-mode, i.e., the presence of two independent plasmas in a low-pressure region.

Numerical investigation for nano-particle synthesis in an RF inductively coupled plasma

Since plasma is regarded as one of the multifunctional fluids which has high energy density, chemical reactivity, controllability by an external electromagnetic field and variable transport properties such as electrical conductivity, it is considerably effective for the synthesis of nano-particles. Since a radio frequency inductively coupled plasma (RF-ICP) has several advantages, the synthesis of ultrafine powders of metals and ceramics with high purity can be easily achieved by the steep temperature gradients at the tail. In the present study, it is clarified how the number density, diameter and specific surface of the produced nano metal-particles of Al, Ti, Au and Pt are influenced by the operating conditions such as the quenching gas flow rate and the powder feed rate of the RF-ICP reactor by numerical investigation. For all the metals, the increase in the quenching gas flow rate results in the increase in the particle number density, the decrease in the mean diameter and the increase in the specific surface. The increase in the powder feed rate causes the increase in the mean diameter but the decrease in the specific surface. The results of four metals are markedly different from each other due to their own material properties of saturation pressure and surface tension.

Computational simulation of a particle-laden RF inductively coupled plasma with seeded potassium

In the present study, the plasma properties, the thermofluid fields and the induction electromagnetic fields and further the in-flight particle behaviors in the radio frequency inductively coupled plasma (RF-ICP), which is electrically enhanced by seeding potassium vapor, are investigated by computational simulation. Since an electrically enhanced plasma is also influenced considerably by the applied coil frequency, the plasma structure and the in-flight particle behaviors in seeding potassium vapor are correspondingly influenced and have distinctive profiles. Due to the electrical enhancement of RF-ICP with potassium seeding, the frequency effect on particle heating becomes more considerable.

Numerical simulation of a potassium-seeded turbulent RF inductively coupled plasma with particles

Seeding a small amount of vaporized potassium with low ionization potential into plasma is one of the effective methods for the enhancement of the electrical conductivity of plasma, which strongly affects the thermofluid fields. In the present study, the thermofluid fields and the particle behavior in the radio frequency inductively coupled plasma (RF-ICP) with electrical enhancement by seeding vaporized potassium are numerically investigated for laminar flow and turbulent flow. The behaviors of four kinds of particles injected into the electrically enhanced plasma were obtained with a Lagrangian method. Particle phase change with melting and the particle diameter variation with evaporation, non-continuum effect for smaller particle diameter, turbulent dispersion and interference with eddies were also taken into account. It is shown that, the electrons diffuse widely and the temperature region less than 2000–8000 K shifts downstream in seeding potassium. In the turbulent flow, electrons diffuse more upstream, which results in the expansion of the temperature region to upstream. The injected particles are heated more rapidly and evaporate more intensively in the turbulent flow.

APPLICATION OF MODULATION TECHNIQUES TO ATOMIC EMISSION SPECTROMETRY WITH INDUCTIVELY-COUPLED RADIO-FREQUENCY PLASMA AND RADIO-FREQUENCY GLOW DISCHARGE PLASMA

ABSTRACT Three novel measuring systems for modulation technique to be applied to atomic emission spectrometry are reviewed. A plasma gas modulation technique is employed for an improvement in the detection sensitivity in inductively-coupled radio-frequency plasma atomic emission spectrometry (ICP-AES). Both an amplitude modulation technique and a bias current modulation technique are effective for obtaining better analytical performance in radio-frequency glow discharge optical emission spectrometry (GD-OES). These techniques produce cyclically-changing components in the emission signals by modulating the excitation processes occurring in each plasma. The detection with a lock-in amplifier plays an important role in these measuring systems; the modulated component of the emission intensities can be selectively detected whereas any noises are completely removed. Furthermore, the background levels are generally less effected by the plasma modulation. These benefit yield the emission signals having larger signal-to-noise ratios as well as larger signal-to-background ratios and therefore the analytical results with better precision and sensitivity.

The deposition of chromium by the use of an inductively-coupled radio-frequency plasma torch

This paper discusses attempts to deposit a layer of hard Cr metal, with properties similar to those of layers currently obtained by electrolytic methods, onto a metallic substrate using an inductively-coupled, radio-frequency plasma torch (ICP-RF) torch. Preliminary studies indicated that it might be possible to produce a suitable layer using a number of chromium-based compounds. For this study, Cr powders and a chromium precursor were injected into the high temperature region of the plasma plume, where thermal decomposition of the feed material produced Cr atoms that deposited onto the surface of metal substrates placed below the plasma torch. The films produced were examined to determine thickness, chemical compositions, and adherence. Since the goal of the project was to develop a coating method that was not only industrially suitable but also environmentally safe, care was taken to monitor the emissions produced by the system during deposition.

Nitridation Of Sapphire Substrate Using Remote Plasma Enhanced-Ultrahigh Vacuum Chemical Vapor Deposition At Low Temperature

AbstractA remote plasma enhanced-ultrahigh vacuum chemical vapor deposition (RPE-UHVCVD) system equipped with a radio frequency-inductively coupled plasma (RF-ICP) which produces the reactive nitrogen species was employed to study the nitridation process at low temperature. The sapphire surface nitridated under various conditions was investigated with x-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The nitridation process seems to be mostly affected by the RF power even at low temperature since the intensity of the N1s, peak was not dependent on the substrate temperature but on the RF power. The AFM images showed that the protrusion density on the sapphire surface decreased rapidly when the nitridation temperature was decreased. This result suggests that the formation of the protrusions is closely related to the process temperature, indicating that the formation of such protrusions is caused by the change of an elastic strain energy due to the thermal stress. It was possible to nitridate the sapphire surface without protrusion at a very low temperature. The crystallinity of GaN grown at 450 °C was found to be much improved when the sapphire substrate was nitridated at low temperature prior to the GaN layer growth.

Performance analysis of a radio-frequency induction plasma generator using nonlinear state-space approach

A free-running induction plasma generator was numerically simulated using an iterative nonlinear state-space method. The reflected resistance of the radio-frequency induction-coupled plasma (RF-ICP), together with its inductance, were extracted from a two-dimensional (2-D) model of RF-ICP and were represented in the generator circuit model as an equivalent resistor and inductor. Matching of the generator's operating condition with that of the RF-ICP was achieved iteratively. The model is able to predict local plasma conditions, coupling efficiency, and the steady-state output signals of the generator. The model can serve as a design tool for the induction plasma generator.

Temperature and density measurements in a recombining argon plasma with diluent

Spectroscopic and callorimetric measurements of temperature arid number density have been made using a 50-kW radio-frequency inductively coupled plasma (RFICP) torch operated at atmospheric pressure with maximum temperatures and electron densities near 8,1000 K and 2 x 1021 m3, respectively These measurements enabled the determination o/ the stale o/ equilibrium and of the corresponding applicability of rarious diagnostic techniques in hoth a recombining argon plasma and a recombining plasma with hydrogen or nitrogen. Results indicate that the Pure argon plasma is well described by u partial equilibrium model in which the free and bound-excited electrons are in mutual equilibrium irespective of possible departures from equilibrium with the ground state. The addition of just tenths of a percent of either atomic Hydrogen or nitrogen, however, disturbs this partial equilibrium hr argon plasmas with electron densities roughly less than 1021 m3 such that only diagnostic techniques which are independent o/ partial equilibrium assumptions can be reliably implemented.

Application of an argon-nitrogen inductively-coupled radiofrequency plasma (ICP) to the analysis of geological and related materials for their rare earth contents

An account is given of the development of a procedure for the determination of the rare earth (RE) elements in a large variety of geological materials employing a medium power argon-nitrogen ICP coupled with a 3.4m Ebert spectrograph. The effects of the carrier and intermediate gas flow rates, height of observation and power on RE spectral line intensities have been studied. The line-to-background ratio of the RE analyte was found to increase with observation height and passed through a maximum at 12–14 mm above the top of the work coil. The method eventually developed allows the direct determination of the lanthanides and yttrium at the 50–200 μg g −1 levels using a single solution prepared by fusing 0.2–1 g samples with Na 2O 2 or LiBO 2 and dissolving the melt in 4–10% (v/v) HNO 3, or by treating the samples with HF-HClO 4-HNO 3 mixtures. For lower contents of the RE elements, they can be separated from matrix concomitants by ion exchange employing AG50W-X8 resin. A large variety of silicate and phosphate reference materials was analysed using scandium as the internal standard. The relative standard deviations vary from about 1.5–15%. No matrix effects were observed despite the large compositional variation of the samples analysed.