Increase Of Discharge Power Research Articles

Etching behaviour of pure and metal containing amorphous carbon films prepared using filtered cathodic vacuum arc technique

A preliminary study on the etching behaviour of pure and metal containing amorphous carbon (a-C) films has been studied using reactive ion etching (RIE) as well as reactive ion beam etching (RIBE). The RIE etching of a-C films, prepared from pure and 1 at.% Al containing carbon cathodes, displays a significant increase in etching rate with increase in discharge power. The inclusion of even a small percentage of metal causes a drastic reduction in the etching rate. The films that contain higher percentages of metal become more difficult to etch using RIE with oxygen plasma. Therefore, etching of the samples by RIBE technique using a plasma mixture of oxygen and argon has been carried out. A significant reduction in the etching rate with increasing metal content was observed for both Al and Ti containing a-C films. This led us to try etching of Ti containing a-C films by RIE technique using a plasma mixture of CF 4 and oxygen. The result shows that the etching rate increases with increasing Ti content. The analysis of the etched surfaces measured by visible Raman indicates that all the surfaces remain almost the same regardless of the processes undergone. However, the morphology measured using Atomic Force Microscopy (AFM) shows that the surface roughness increases significantly after etching, especially for the pure carbon films.

Decomposition of dilute trichloroethylene by nonthermal plasma

Decomposition performance of a dilute toxic organic compound, trichloroethylene (TCE), in air by using nonthermal plasma processing was studied extensively. The nonthermal plasma was generated by the high-frequency (2 kHz) or commercial-frequency (50 Hz) barrier discharge in a fused silica tube. Three types of reactors, bolt type, rod type (both are barrier-discharge type), and coil type (surface-discharge type), were tested. Analysis of byproducts, residual materials, and end products generated by the plasma process was performed by a gas chromatography mass spectrometer or gas chromatography. Most organic byproducts decrease with an increase of the electric discharge power, but only toxic phosgene increases with the increase of the discharge power. As a post process, NaOH solution was used to test effluent from the plasma reactor. The solution was found effective in phosgene absorption. Comparison between nonthermal plasma and UV irradiation for TCE decomposition was also made. In regard to the energy efficiency of TCE decomposition, UV irradiation is found much better than discharge plasma.

Hysteresis and the E-to-H transition in radiofrequencyinductive discharges

Typical inductive discharges, such as are used for plasma processing, exhibit two modes of operation: the true inductive discharge known as the H mode, and a weak capacitive discharge known as the E mode. Experimentally, the transition between these modes as the coil current is increased is clear and is marked by a large increase in discharge power, plasma density and optical emission occurring as the H mode appears. According to simple theory, this transition and the reverse transition occur at a single well defined current. In practice, this is usually not the case. The E-to-H transition occurs at a larger coil current than the H-to-E transition, and a range of currents between these values supports either E or H mode. This effect is called hysteresis. In this paper we show that hysteresis can be understood to arise from nonlinear effects, most notably in the electron power balance equation. We survey various mechanisms that can produce hysteresis and attempt to provide quantitative estimates of their significance.

The altered layer formation during the reactive ion etching of GaAs in CF 2Cl 2+O 2 plasma

The reactive ion etching of GaAs (100) in CF 2 Cl 2+O 2 plasma is reported. The RF plasma was excited in a diode asymmetrical system with accelerating potential of 300–1500 V, discharge power of 0.5–5.0 W\\cm 2 and pressure of 10 −2–10 Pa. The experimental measurements have shown that with the increase of discharge power in plasma the surface becomes depleted by arsenic and enriched by gallium oxide. The experimental curves were modeled by proposed phenomenological model. The model includes the main processes taking place during reactive ion etching : sputtering, adsorption, heterogeneous chemical reactions, desorption of volatile compounds and radiation enhanced diffusion. As the balance equations are written for each component in each monolayer the model gives the kinetics of elemental composition on the surface and the composition of the altered layer.

Structure and surface properties of plasma polymerized acrylic acid layers

AbstractThin plasma polymerized layers of acrylic acid (PPAA) were deposited onto polyethylene and muscovite mica surfaces. Structure and surface properties of the deposited layer depend on the polymerization conditions. The content of carboxylic groups in the layer decreases, whereas the degree of crosslinking or branching increases, with increasing discharge power. A soft, sticky layer with a low contact angle against water is obtained when a low discharge power (5 W) is used. In contrast, a hard film with a rather high water contact angle is obtained when the discharge power is high (50 W). A surface force apparatus was employed to study some film properties including adhesion force, crack formation, and capillary condensation. The adhesion force between plasma polymerized acrylic acid layers prepared at a low discharge power is high in dry air. It decreases remarkably in humid air and no adhesion is observed in water. In dry air, the adhesion force between PPAA layers decreases as the discharge power increases.

Nonequilibrium Argon Induction Plasmas by a Two-Temperature Model

The nonequilibrium behavior of induction argon plasmas at a pressure 1.0 aim is studied by means of a two-temperature model. The results are compared with Stokes' experiments and with the LTE plasmas. The agreement with the experiments is well improved compared with the agreement using the LTE theory. The electron temperature has an off-axial peak in the profile and deviates considerably from the heavy gas temperature in the outer region. On the other hand, the temperature difference between them in the central region is fairly small even for relatively low axial temperatures. Although for a low power discharge the gas temperature decreases monotonically toward the wall, it drops but is slightly higher than the electron temperature in the central region, when the discharge power increases.