Effects Of Argon Gas Pressure Research Articles

Characteristic Diagnostics of a Laser-Stabilized High-Pressure Argon Plasma by Optical Emission Spectroscopy

Laser-stabilized plasma (LSP) attracts intense interests in lighting applications requiring extreme stability, long lifetime, and broad radiation range ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10^{1}$ </tex-math></inline-formula> – <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10^{4}$ </tex-math></inline-formula> nm). In this work, an argon LSP was generated at high pressures (>10 bar) by a focused laser beam, and its fundamental properties were studied in detail by the approach of optical emission spectroscopy (OES), with emphasis on the determination of plasma parameters including the electron temperature and density. The effects of argon gas pressure, laser power, and N2 mixture ratio, on the full-view of radiation spectra and electron parameters, were investigated experimentally. The results demonstrate that the increase of gas pressure or laser power density is a proper way to achieve higher optical radiation from the argon LSP, but not by adding molecular mixtures like N2.

Influence of deposition pressure on properties of ZnO: Al films fabricated by RF magnetron sputtering

Transparent conductive aluminum doped zinc oxide (ZnO:Al, AZO) films were prepared on glass substrates by rf (radio frequency) magnetron sputtering from ZnO: 3wt% Al2O3 ceramic target. The effect of argon gas pressure (PAr) was investigated with small variations to understand the influence on the electrical, optical and structural properties of the films. Structural examinations using X-ray diffraction (XRD) and scanning electron microscopy (SEM) showed that the ZnO:Al thin films were (002) oriented. The resistivity values were measured by four-point probe with the lowest resistivity of 5.76×10-4 Ω·cm (sheet resistance=9.6 Ω/sq. for a thickness=600 nm) obtained at the PAr of 0.3 Pa. The transmittance was achieved from ultraviolet-visible (UV-VIS) spectrophotometer, 84% higher than that in the visible region for all AZO thin films. The properties of deposited thin films showed a significant dependence on the PAr.

The effect of argon gas pressure on structural, morphological and photoluminescence properties of pulsed laser deposited KY3F10:Ho3+ thin films

KY3F10:Ho3+ thin films were deposited by a pulsed laser deposition technique with Nd–YAG laser radiation (λ = 266 nm) on (100) silicon substrate. The XRD and FE-SEM results show improved crystalline structure for the film deposited at a pressure of 1 Torr. The AFM results show that the RMS roughness of the films increases with rise in argon gas pressure. The EDS elemental mapping shows Y-excess for all the films deposited under all pressures, and this is attributed to its higher mass and low volatility as compared to K and F. XPS analysis further confirmed Y-excess in the deposited films. Green PL emission at 540 nm was investigated at three main excitation wavelengths, namely 362, 416 and 454 nm. The PL emission peaks increase with rise in background argon gas pressure for all excitation wavelengths. The highest PL intensity occurred at excitation of 454 nm for all the thin films. In addition, faint red (near infrared) emission was observed at 750 nm for all the excitations. The green emission at 540 nm is ascribed to the 5F4–5I8 and 5S2–5I8 transitions, and the faint red emission at 750 nm is due to the 5F4–5I7 and 5S2–5I7 transitions of Ho3+.

Effect of argon gas pressure on residual stress, microstructure evolution and electrical resistivity of beryllium films

The residual stress in beryllium films fabricated on K9 substrates by using magnetron sputtering deposition is measured by using a curvature method and is theoretically estimated by using the Nix and Clemens (NC) model. The experimental results indicate that the 1.3-μm-thick film is always in a tensile state for pressure variations in the range from 0.4 to 1.2 Pa. When the sputtering gas pressure is increased, the average stress increases at first, after which it decreases by a remarkable amount. The observed descending trend of the tensile stress when the sputtering gas pressure is beyond 0.6 Pa is mainly attributed to the grain size in the film being larger than that in the film when the pressure is below 0.6 Pa. The maximal residual stress of 552 MPa at a sputtering gas pressure of 0.6 Pa is close to the tensile strength (550 MPa) of the corresponding beryllium bulk material and is about 8 times smaller than that calculated by using the N-C model. In addition, the surface morphologies of the as-fabricated films reveal fibrous grains while the cross-sectional morphologies are characterized by a coarsening of columnar grains. The measured electric resistivity of each film strongly depends on its porosity and the sizes of its grains.

Effects of argon gas pressure on its metastable-state density in high-density plasmas

The effect of argon gas pressure on its metastable density in inductively coupled plasmas (ICPs) is investigated by using the laser-induced fluorescence method. Our results show that the metastable-state density of argon varies with the gas pressure depending on the measurement position; the density decreases with the pressure at a position far from the ICP antenna, whereas it increases with the pressure at a position near the antenna. This contrast in the metastable-state density trend with the pressure is explained by considering the electron temperature variations at the two measurement positions. The theoretical interpretation and calculation using a global model are also addressed in detail in this paper.

Influence of Energy Deposition on Characteristics of Nanopowders Synthesized by Electrical Explosion of Aluminum Wire in the Argon Gas

The energy deposition during the wire electrical explosion process plays an important role in the expansion of metallic vapor and conductive plasma for the nanopowders preparation. In this paper, aluminum nanopowders are synthesized by electrical exploding aluminum wire in the argon gas under different charging voltages of the capacitor. The influence of the deposited energy E and the argon gas pressure p on the characteristics of aluminum nanopowders is studied by the transmission electron microscope (TEM). Due to the effect of argon gas pressure on the energy deposition, a plasma expansion parameter $Ep^{-1}$ is proposed to summarize the synthesis conditions. The results show that the morphology of aluminum nanopowders was mainly dependent on the argon gas pressure rather than deposited energy. Lower deposited energy and higher pressure of argon gas could broaden the particle size distribution range of aluminum nanopowders evidently, which is ascribed to a smaller plasma expansion volume. The count mean diameter of aluminum nanopowders decreases monotonically with the increasing plasma expansion parameter $Ep^{-1}$. The value of relative standard deviation ranges from 0.38 to 0.5 in the experiments. It has been demonstrated that the size uniformity of nanoparticles can be improved by reducing the energy deposition rate when the pressure of argon gas and deposited energy remains virtually unchanged.

Effect of Argon Gas Pressure on Optical Properties of Zinc Oxide Thin Films Deposited by RF Magnetron Sputtering Technique

Zinc oxide (ZnO) thin films were deposited by radio frequency (RF) magnetron sputtering technique on glass substrates in pure argon gas. The optical transmission stectra of the films were measured by ultraviolet-visible spectrophotometer. The effects of argon gas pressure on optical properties of the deposited films were investigated. The optical band-gap of the films was evaluated in terms of the Taucs law. The results show that the argon gas pressure has slightly affected the optical band-gap of the deposited films. Furthermore, the refractive index and extinction coefficient of the films were determined by means of the optical characterization methods. Meanwhile, the dispersion behavior of the refractive index was studied by the single-oscillator model of Wemple and DiDomenico, and the physical parameters of the average oscillator strength, average oscillator wavelength, oscillator energy, the refractive index dispersion parameter and the dispersion energy were obtained.

Study on Electronic Excitation Temperature of Argon Plasma Using Low Pressure Micro-ICP Excitation Source

Electronic excitation temperature is an important indicator of the spectrometer excitation source. This work experimented self-made micro-ICP excitation spectroscopy based on PCB technology, and detected 17 spectral lines in 690~860 nm of argon atom. 763.51 nm and 772.42 nm spectral lines whose wavelengths are close to were used to calculate electronic excitation temperature of argon excited by micro-ICP, and results show in 1600~3000 K. Experimental test data shows effects of argon gas pressure on electronic excitation temperature that in 20~210 Pa electronic excitation temperature increases with pressure on the whole. When argon pressure is greater than 220 Pa, plasma flame flickers and the electronic excitation temperature shows greater fluctuation; Experimental test shows effects of RF power on electronic excitation temperature that in 3~23 W electronic excitation temperature gradually increases with RF power. Causes of electronic excitation temperature with pressure, RF power variation are analyzed.

The Effect of Argon Gas Pressure on Ice Ball Size and Rate of Formation

Contemporary cryoablation technology utilizes the Joule-Thomson effect, defined as a change in temperature that results from expansion of a nonideal gas through an orifice or other restriction. We evaluated the effect of initial gas tank pressures on freezing dynamics in a single-probe model and in a multiprobe model using contemporary cryoablation technology. Cryoablation trials were performed in a standardized system of transparent gelatin molds at 25°C. Two sets of trials were performed. The first trial evaluated temperature and ice ball size for a given tank pressure when a single needle was deployed. The second trial recorded ice ball temperatures for each probe when multiple probes were fired simultaneously. Trial 1: The rate of temperature change is directly related to the initial pressure of the gas being released, and the group with the highest starting pressures reached the lowest mean temperature and had the largest mean ice ball size (p < 0.01). Trail 2: Multiple-probe ablation did not affect the rate of temperature change or final temperature compared with firing a single probe (p > 0.7). In accordance with the Joule-Thomson effect, higher initial gas pressures used for cryoablation in a transparent gel model demonstrate statistically significant lower temperatures, faster decreases in temperature, and formation of larger ice balls than lower gas pressures do. With contemporary technology, multiple simultaneous cryoprobe deployment does not compromise individual probe efficacy. The use of higher initial tank pressures will theoretically help future cryoprobes be more effective, creating a greater volume of cell necrosis and a smaller indeterminate zone.

Effect of electron energy probability function on plasma CVD/modification in a 13.56 MHz hollow cathode discharge

Langmuir probe diagnostics is done on a RF hollow cathode discharge system (13.56 MHz, 200 W) by inserting a single cylindrical probe in the remote region (50 mm away from the primary argon plasma) and at a distance of 10 mm above the substrate holder. The effects of argon gas pressure, the injection of helium in the remote zone and the substrate bias on the measurements of the electron energy probability function (EEPF) and on the plasma parameters (electron density (ne), effective electron temperature (Teff), plasma potential (Vp) and floating potential (Vf)) have been investigated. The EEPFs and plasma parameters obtained have been used to control two remote plasma processes. The first is the remote plasma enhanced chemical vapour deposition (PE-CVD) of thin films, on silicon wafers, from a hexamethyldisiloxane precursor diluted in the remote Ar–He plasma, where the relative thicknesses of the deposited films were investigated by the ex situ Rutherford back-scattering (RBS) technique. The second is the pure argon remote plasma treatment of a polymethylmethacrylate polymer surface, where the reflectance of the modified surface was measured and compared with the untreated one. It is revealed that by varying the gas mixture/pressure and substrate bias, one can engineer the EEPFs to enhance the desired plasma chemical gas phase reactions thus controlling the plasma CVD and plasma surface modification processes. Auxiliary optical emission spectroscopy diagnostics are discussed as well.

Investigation of the Formation and Energy Density of High-Current Pulsed Electron Beams

High-current pulsed electron beams (HCPEB) irradiation is a new potential method to polish hard steels and alloys. After HCPEB machining, the performance of machined surface, such as corrosion resistance and microstructure, has been greatly improved. Because of its good performance, HCPEB irradiation is playing more and more important roles in polishing hard steels and alloys. However, it is not clear about the energy density of HCPEB under different beam conditions. In this study, experiments have been conducted to investigate the formation of HCPEB and its energy density. Then, effects of argon gas pressure and the applied voltage to solenoid coil on the formation of HCPEB are analyzed. Finally, a mathematical model is developed to describe the relationship between five dominant beam parameters with the energy density of HCPEB, which has a good accuracy in comparison to the experimental results.