The Influence of Cleaning Parameters in High-Density Argon Plasma on the Surface Morphology of Glass Substrates and the Characteristics of the Emission Spectrum

Photoemission‐assisted plasma irradiation of a 2″ Cu substrate was performed to clarify the effect of ion impingement on the substrate. With the use of a photoemission‐assisted plasma apparatus, the photoemission‐assisted plasma was evaluated by optical emission spectroscopy and discharge characteristics. The density ratio of Ar ions and atoms increases with increasing the bias voltage of photoemission‐assisted plasma. Changes in the surface morphology of the substrate were investigated using atomic force microscopy. Sufficient ion density can be obtained in photoemission‐assisted Townsend discharge, and surface roughness of the Cu substrate decreased as the plasma irradiation time increased. This result indicates that ion impingement from photoemission‐assisted Townsend plasma can sputter the metal surfaces, leading to a decrease in surface roughness. Copyright © 2011 John Wiley & Sons, Ltd.

Effects of interface micro structure in crystallization of ZnO thin films prepared by radio frequency sputtering

Abstract: In this work, we measure the plasma parameters by using an AC high-voltage power supply that generates a non-thermal plasma jet system at atmospheric pressure. A nickel (Ni) metal strip, with dimensions of 1.5 × 10 cm2, was connected to the anode electrode of the AC power supply. This nickel strip was immersed in a flask with a small amount of distilled water positioned below the plasma plume nozzle. Optical emission spectroscopy (OES) was used to diagnose the plasma system at different argon gas flow rates (1-5 L/min) and varying applied voltage values (11-15 kV). It is significant to know the processes accompanying plasma generation to measure their parameters which include the electron temperature (Te), electron number density (ne) of the plasma, Debye length (λD), and plasma frequency (fp). Our results showed an increase in the intensity of spectral lines with the increase in applied discharge voltage (11-15 kV). The maximum peak for ArI was observed at a wavelength of 811.531 nm, and the maximum peaks for nickel (Ni) were observed at wavelengths of 285.21 and 519.70 nm. Also, the results indicated a gradual increase in electron temperature (Te) and electron density (ne) values at the applied voltage of 0.403-0.468 eV. Likewise, the electron density (ne) was in the range of (11.486-13.851) × 1017 cm-3. Keywords: Atmospheric plasma jet, Nickel (Ni) plasma parameters, Electron temperature, Spectroscopic optical emission (OES).

Adjusting surface morphology of substrate to improve the capacitive performance for the formed boron-doped diamond electrode

A uniform plasma plume was generated in a coaxial dielectric barrier discharge jet through blowing argon into the ambient air at atmospheric pressure. The plasma plume was uniform along the direction of the gas flow. The length of the plasma plume was investigated as a function of the peak voltage, the driving frequency and the gas flow rate. It was found that with increasing the gas flow rate, the plume length increases when the flow rate is lower than 4 L x min(-1), and decreases when it is higher than 4 L x mic(-1). Under constant gas flow rate, the length of the plasma plume increases with the increase in the peak value of the applied voltage and the driving frequency. According to the discharge theory and based on the analysis of the turbulence and the advection, a qualitative explanation was given for the variance of plume length as functions of the experimental parameters. Results also show that there is a discharge pulse for the plasma plume in every positive half cycle, while there is no pulse in negative half cycle. The coaxial dielectric barrier discharge shows two pulses in every positive half cycle and a pulse in every negative half cycle. Analyzing these experimental phenomena mentioned above, a formation mechanism of the plasma plume was proposed. The optical emission spectra were obtained for both the coaxial dielectric barrier discharge and the plasma plume. There was no apparent difference except that some emission lines from reactive species such as OH and N2 were found in the plasma plume. Using the first negative band of, the rational temperature of the plasma plume was measured. Results show that the rational temperature of the plasma plume decreases away from the jet nozzle, and increases with increasing the peak value of the applied voltage.

Optical emission spectra and ion energy distribution functions in TiN deposition process by reactive pulsed magnetron sputtering

Since the first inductively coupled plasma (ICP) torch was developed in the 60's, RF thermal plasmas have found a variety of applications in material processing such as crystal growth, thermal spray coatings, spheroidization and vaporization of refractory materials. In recent decades, inductively coupled thermal plasmas have been used for the synthesis of high purity nanoparticles, thank to their remarkable advantages such as high energy density, variable operating pressures and low product contamination. The formation of nano-sized particles in thermal plasmas particularly using solid refractory precursor is a complex process. Hereby the injected precursor powders are heated by the high temperature of the thermal plasma. The heated powders are vaporized and decomposed into vapor species. During the following cooling, the vapor species are condensed to nano-sized particles. In this synthesis process, characterized by evaporation-condensation, the properties of the synthesized particles such as particle size, size distribution, phases and morphology are affected by various process parameters. Gas pressure, flow rates of the different torch gases, size of the precursor powders and powder loading in the plasma are considered as the influencing process parameters. In order to optimize and control the process for tailor-made nanoparticle synthesis, it is necessary to understand the effects of the process parameters on plasma properties and on the particle-plasma interactions resulting in final properties of the synthesized powders. In the present work, firstly, the enthalpy probe technique, a well-established plasma diagnostic tool for high pressure thermal plasma, has been applied to characterize the inductively coupled Ar-H2 thermal RF plasma used for alumina nanoparticle synthesis at different operating conditions. The plasma enthalpy has been determined, and the plasma temperature under a given gas pressure could subsequently be calculated assuming local thermodynamic equilibrium (LTE), once the gas composition has been determined by mass spectrometry. The gas velocity of the plasma jet could also be obtained by using the Bernoulli equation and stagnation pressure. Secondly, the influence of flow rates of central gas and precursor feed rates on the Al2O3 precursor evaporation has been investigated by process monitoring. Optical emission spectroscopy (OES) and laser light extinction (LE) measurements have been carried out to monitor in-situ the injection of the alumina precursors and to obtain information on the ongoing precursor evaporation. The emission line intensities of the aluminum vapor were used to determine the dependence of process parameters on precursor evaporation. Furthermore, the laser light extinction was used to calculate the number density of non plasma-treated powders, from which the number fraction of evaporated powders could be deduced. The size and morphology of the synthesized particles have been characterized ex-situ. Finally, the influence of quenching conditions on the condensation and formation of the nano-sized alumina particle has been studied by process analysis of the gas phase reactions of alumina. Optical emission spectroscopic was performed at different axial positions to monitor the gas phase reactions of the vaporized particles. Axial profiles of the emission line intensities of the main vapor species of alumina, Al(g) and AlO(g), were compared with the results of the enthalpy probe measurements and the thermal decomposition reactions of alumina found in literature. The results allow explanation of the alumina reactions in the thermal plasma as well as gives indications for the optimal axial position of the quenching gas injection. In addition to the determination of the optimal quenching position, the influence of the flow rates of quenching gas on the nanoparticle formation has been investigated. The synthesis of the submicron alumina using vapor-condensation principle predominantly leads to various thermodynamically metastable crystal structures called transition alumina. Therefore, the occurrence of different transition aluminas is discussed with regards to the flow rates of the quenching gas. The results presented in this thesis show that the synthesis process of the nanoparticle can be described on the basis of experimental results and basic information on the powder materials. The explanation of the influence of process parameters on powder evaporation and nanoparticle formation shows the usefulness of the in-situ plasma process monitoring, and the large potential for optimizing and controlling the nanopowder synthesis process in an inductively coupled RF thermal plasma.

In this work, the bacteria inactivation using the nonthermal atmospheric pressure plasma has been studied. The bacteria inactivation was conducted using a self-design nonthermal atmospheric pressure plasma jet system. During this experiment, Escherichia coli was used as an objective microorganism. The primary operating gas for the plasma jet used in this work is helium, and small fractions of oxygen or nitrogen (0.2%) were used as the secondary gas. The three plasma jet cases were operated at 3.5 kV, 14 l/m, and 7 mm, which represented the applied voltage, gas flow rate, and distance from the nozzle, respectively. The types of reactive species have been examined using optical emission spectroscopy. The gas temperature and optical emission spectrum were measured under the same condition. The active species of OH, OII, OI, N21+, N22+, and He are indented in the UV-vis wavelength range. The inactivation of E. coli bacteria has occurred after 20 s of nonthermal plasma treatment, whether the carrier gas is pure helium or helium + nitrogen or helium + oxygen. The results revealed that the impact of helium is less than that of helium + 0.2% nitrogen which is less than that of helium + 0.2% oxygen. The current results of this experiment could be utilized in improving the nonthermal plasma jet for extended surface decontamination.

In this paper, we propose two new approaches for preparing active substrates for surface-enhanced Raman scattering (SERS). In the first approach (method 1), one transfers AgI nanoparticles capped by negatively charged mercaptoacetic acid from a AgI colloid solution onto a quartz slide and then deoxidizes AgI to Ag nanoparticles on the substrate. The second approach (method 2) deoxidizes AgI to Ag nanoparticles in a colloid solution and then transfers the Ag nanoparticles capped by negatively charged mercaptoacetic acid onto a quartz slide. By transfer of the AgI/Ag nanoparticles from the colloid solutions to the solid substrates, the problem of instability of the colloid solutions can largely be overcome. The films thus prepared by both approaches retain the merits of metal colloid solutions while they discharge their shortcomings. Accordingly, the obtained Ag particle films are very suitable as SERS active substrates. SERS active substrates with different coverages can be formed in a layer-by-layer electrostatic assembly by exposing positively charged surfaces to the colloid solutions containing oppositely charged AgI/Ag nanoparticles. The SERS active substrates fabricated by the two novel methods have been characterized by means of atomic force microscopy (AFM) and ultraviolet-visible (UV-vis) spectroscopy. The results of AFM and UV-vis spectroscopy show that the Ag nanoparticles grow with the increase in the number of coverage and that most of them remain isolated even at high coverages. Consequently, the surface optical properties are dominated by the absorption due to the isolated Ag nanoparticles. The relationship between SERS intensity and surface morphology of the new active substrates has been investigated for Rhodamine 6G (R6G) adsorbed on them. It has been found that the SERS enhancement depends on the size and aggregation of the Ag particles on the substrates. Especially, we can obtain a stronger SERS signal from the substrate prepared by method 1, implying that for the metal nanoparticles capped with stabilizer molecules such as mercaptoacetic acid, the in situ deoxidization in the film is of great use in preparing SERS active substrates. Furthermore, we have found that the addition of Cl- into the AgI colloid solution changes the surface morphology of the SERS active substrates and favors stronger SERS enhancement.

An experimental setup was built up to carry out radio frequency (RF) inductively coupled plasma (ICP) and dielectric barrier discharge (DBD), and to depict the optical emission spectra (OES) of the discharges. OES from argon ICP and DBD plasmas in visible and near ultraviolet region were measured. For argon ICP, the higher RF power input (higher than 500 W for our machine), the higher degree of argon plasma ionization. But that doesn't mean a higher mean electron energy. With the increase in the power input, the mean electron energy increases slightly, whereas the density of electron increases apparently. Or, the contrary, argon DBD discharge behaves in the manner of a pulsed DC discharge on optical emission spectroscopy and V-I characteristics. DBD current is composed of a series of pulses equally spaced in temporal domain. The kinetics of DBD emission strength is mainly governed by the frequency of the current pulse.

Effect of basal plane bending on the atomic step morphology of the 4H–SiC substrate surface

Measurements of optical attenuation and emission spectra for the radiating bow shock region upstream of several ablating arc jet test models are reported. Attenuation measurements were intended to assess light transmission parallel to the model face at k633 nm by the shock layer formed over the ablating surface; the attenuation is attributed to the presence of particles. As the models ablated, the surface receded, effectively translating the detection line of sight upstream from the model surface. Substantial loss of transmission correlated with the macroscopic ablation and surface heating rates, and persisted upstream of the shock front. Simultaneously, optical emission spectra were measured in the same plane as the attenuation laser. These measurements were intended to determine the extent to which ablation products (particles or vapor) influence the bow shock radiation. The spectra were measured rapidly using miniature fixed-grating spectrometers with fiber optic input. With a field of view of 2 mm and acquisition time less than 100 ms, spatial resolution was retained and time dependent intensity trends were observed. Several components of dissociated air can be identified based on their spectral signatures; the radiative contribution by ablation products appears minor, however.

The relationship between µc-Si:H solar cell performance and surface morphology of substrate is studied systematically using textured-ZnO substrate which is formed by wet etching process in order to clarify the optimum morphology of substrate for high efficiency. An average slope, tan θ, of substrate surface textures is obtained by analysis of atomic force microscopy (AFM) images, and solar cell performance is correlated with the value os tan θ. As a result, because of the balance between the optical confinement and the grain boundary formation, a conversion efficiency shows a maximum at a tan θ of 0.08 which is 3 times smaller as compared to that used for a-Si:H. An efficiency of 9.4% (Voc=0.526 V, Jsc=25.3 mA/cm2, FF=0.710) is obtained at a deposition temperature of 140°C using the optimized morphology.

Deposition of nano-diamond-like carbon films by an atmospheric pressure plasma gun and diagnostic by optical emission spectrum on the process

A Penning ion source with self-heated cathodes has been applied in a miniature cyclotron. Optimizing the formation of negative hydrogen ions in the ion source needs the knowledge of plasma parameters. Optical emission spectroscopy is introduced as a noninvasive and in situ diagnostic tool for line-of-sight averaged plasma parameters in this paper. The relative intensities of neutral atomic hydrogen emission spectral lines are used to evaluate the electron temperature of hydrogen plasma. The experimental results show that the relative intensities of Balmer lines (H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">α</sub> , H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">β</sub> , and H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">γ</sub> ) display significant dependence on gas flow rate, not sensible to arc current and magnetic field. The calculated electron temperature is in the range of 4000-7000 K in the experiments. The correlations of electron temperature with arc current, gas flow rate, and magnetic field are discussed, respectively.