Addition Of O2 Gas Research Articles

A Study on Dielectric Breakdown Properties of Hot CO2/O2/C5F10O Gas Mixture: Focus on Concentration Rate of O2 Gas

A gaseous mixture of CO2 and C5F10O has been widely investigated as one of the alternative gases for SF6. Due to the better electron attachment ability of oxygen molecule O2, it is generally expected that adding of O2 gas would improve the dielectric strength of arc quenching and insulating gas for electric power equipment. Therefore, in this paper, the dielectric breakdown properties of hot CO2/O2/C5F10O gas mixture were numerically estimated. The calculation results revealed that the critical electric field strength of the CO2/C5F10O gas mixture is disappointingly decreased by the addition of O2 gas, especially in the temperature range of 3000 K to 1000 K. This is brought about by the increase of ionization reaction of CO2 molecules with an increase in the O2 concentration in the arc‐quenching gas of CO2/O2/C5F10O. © 2024 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.

Effects of O2 gas addition on enhancing lithium electrochromic performance of flexible WFexTayOz1Cz2Nz3 films synthesized by cold atmospheric pressure plasma polymerization

Improved lithium electrochromic (EC) performance of flexible organo-tungsten-iron-tantalum oxynitride (WFexTayOz1Cz2Nz3) films by rapidly deposited onto flexible (60 Ω/□ polyethylene terephthalate/indium tin oxide) substrates at a short exposure duration of 54 s, with O2 gases added to precursor vapors, and injected into air plasma jet, was undertaken. O2 gases addition for synthesis of WFexTayOz1Cz2Nz3 films by cold atmospheric pressure plasmas polymerization was proven to significantly enhance optical modulation at a wavelength of 850 nm from 59.7% without addition of O2 gases to 70.0% with addition of O2 gases at a flow rate of 0.5 sccm. WFexTayOz1Cz2Nz3 films synthesized with O2 gas addition at a flow rate of 0.5 sccm exhibit fast coloration and bleaching responses as the short coloration time up to 5.1 s and the short bleaching time up to 3.7 s were obtained. Surface morphology and surface compositions of WFexTayOz1Cz2Nz3 films were analyzed by FESEM and XPS to investigate how the O2 gas addition enhanced the lithium EC properties.

Effect of the addition of O2 on copper etching using high density plasma of acetylacetonate/Ar

In the present study, the high density plasma etching of copper thin films masked with SiO2 was conducted using an acetylacetone/O2/Ar gas mixture. As the concentration of acetylacetone increased, the etch rates for the copper film decreased but the etch selectivity increased. The addition of O2 gas to the acetylacetone/Ar mixture greatly improved the etch profile without the redeposition on the sidewalls of the copper film. This was attributed to the formation of copper compounds containing oxygen with the assistance of a polymeric protection layer. Good etch profile for the copper film was obtained using an acetylacetone/O2/Ar gas mixture with a 4:1 vol ratio of acetylacetone to O2. The proposed acetylacetone/O2/Ar gas mixture thus represents a potential candidate gas for the dry etching of copper films.

Observation of a significant drop of electron density in cascaded arc argon plasma doped with oxygen gas using laser Thomson scattering

In this work, the electron density (n e) and electron temperature (T e) of cascaded arc argon plasma regulated by adding electronegative oxygen gas have been investigated using laser Thomson scattering diagnostic technique. The results indicate that the addition of O2 gas causes a significant decrease of n e, which drops from 1020 m−3 to 1017 m−3. This is mainly attributed to the dissociative recombination reaction between electrons and O2 + molecular ions. Meanwhile, the formation of negative ions, O2 − and O−, consumes electrons and further makes n e decrease. But, T e remains nearly unchanged with the increase of O2 ratio from 0% to 10%. This is probably due to that the electron energy loss by the electron collisions with O2 molecules in the ground state balances the electron heating induced by the super-elastic collisions with the highly vibrational excited O2 molecules.

Influence of admixing oxygen on Ar plasma discharge for organic pollutant degradation in wastewater treatment

In previous study, non-thermal plasma system with addition of O2 gas was proven to accelerate the decolorization process of dye solution, resulting in faster treatment of the synthetic wastewater. The present study deals with the influence of variation of O2 gas admixing to the Ar plasma discharge to examine the decolorization of methylene blue solution underwater through measurement of absorbance value of the plasma-treated solution by UV/VIS measurement. From the experiments it was found that the best result of methylene blue solution decomposition was obtained from the application of Ar 0.3 lpm with the admixing of O2 gas 0.3 lpm in an underwater plasma system generated at 1.56 kV. Modelling the decomposition process of methylene blue by using Ar+O2 plasma with variation of O2 flow rate, it was found that the system was confirmed to follow the first order kinetics equation. From this study it could be said that the plasma-based oxidation process is promising for the application in the decomposition of textile wastewater to support sustainable industry with environmentally friendly orientation.

Chromium oxide as a hard mask material better than metallic chromium

In nanofabrication, use of thin resist is required to achieve very high resolution features. But thin resist makes pattern transferring by dry etching difficult because typical resist has poor resistance to plasma etching. One widely employed strategy is to use an intermediate hard mask layer, with the pattern first transferred into this layer, then into the substrate or sublayer. Cr is one of the most popular hard etching mask materials because of its high resistance to plasma etching. Cr etching is carried out in O2 and Cl2 or CCl4 environment to form the volatile etching product CrO2Cl2, but addition of O2 gas leads to fast resist etching. In this work, the authors show that Cr2O3 can be etched readily in a Cl2/O2 gas mixture with less oxygen than needed for Cr etching, because Cr2O3 contains oxygen by itself. Thus it is easier to transfer the resist pattern into Cr2O3 than into Cr. For the subsequent pattern transferring into the substrate here silicon using nonswitching pseudo-Bosch inductively coupled plasma-reactive ion etching with SF6/C4F8 gas and Cr or Cr2O3 as mask, it was found that the two materials have the same etching resistance and selectivity of 100:1 over silicon. Therefore, Cr2O3 is a more suitable hard mask material than Cr for pattern transferring using dry plasma etching.

Dry etching of palladium thin films in high density plasmas of CH3OH/Ar, C2H5OH/Ar, CH4/Ar, and CH4/O2/Ar gas mixtures

High density plasma etching of Pd thin films masked with TiN films was performed using CH3OH/Ar, C2H5OH/Ar, CH4/Ar, and CH4/O2/Ar gas mixtures. The etch rates of the Pd films and TiN masks in all the gas mixtures decreased whereas the etch selectivities increased. The etch profiles of the Pd films etched under C2H5OH/Ar gas were better than those obtained with CH3OH/Ar gas. Addition of O2 gas to the CH4/Ar gas mixture considerably improved the etch profiles of the Pd films. CH4, Ar, and O2 were found to play a critical role in obtaining a vertical etch profile with smooth sidewalls. Energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy revealed the formation of polymeric layers and PdOx compounds on the sidewalls and the film surface. Good etch profiles with a high degree of anisotropy were achieved with the use of C2H5OH/Ar and CH4/O2/Ar gas mixtures.

Investigation on a source of dominant donor in vanadium-doped ZnO films grown by reactive RF magnetron sputtering

The influences of O2 gas addition in argon plasma on reactive RF magnetron sputtering deposition of vanadium-doped ZnO (VZO) films were examined. ZnO or VZO films with vanadium concentration of 2at% were deposited on a quartz substrate. Vanadium doping caused oxygen deficiency in ZnO and formed a large number of zinc interstitials (Zni), oxygen vacancies (VO), and zinc vacancies (VZn). Carrier density of VZO decreased from 9×1020 to 9×1018cm−3 between O2 partial pressure ratio (αO2) of 0.6% and 1.0% in spite of the increase in valence number of vanadium. This result suggests that Zni is the dominant donor in VZO since Zni is a shallow-level defect. Average optical transmittance (Tv) at wavelength between 450 and 800nm of VZO was 61% while that of ZnO was 82% without oxygen addition. Although the optical transmittance of VZO was largely deteriorated by optical absorption of VO, Tv of VZO improved by oxygen addition and reached 85% at αO2 of 1.0% via suppression of VO formation.

In vitro bactericidal efficacy of atmospheric-pressure plasma jet on titanium-based implant infected with Staphylococcus aureus

Staphylococcus aureus is a representative of gram-positive bacteria that causes skin infection, respiratory diseases, and burned tissue infections. The aim of this study was to evaluate the sterilizing efficiency of an atmospheric-pressure plasma jet (APPJ) on S. aureus adhered on a titanium surface. During the APPJ sterilization, the plasma gases used were Ar, Ar+N2, and Ar+O2. With increasing APPJ treatment time, the viability of S. aureus decreased. The addition of O2 gas to Ar gas resulted in a higher sterilizing efficiency than the addition of other groups. Plasma exposure induced bacterial oxidative stress, and it was confirmed that the cell membrane was seriously damaged by the production of reactive oxygen species. Our finding suggests that the APPJ is an effective tool for clinical antimicrobial therapy.

Plasma polymerized allyl alcohol/O2 thin films embedded with silver nanoparticles

The simple production of a new type of anti-bacterial polymer coating with embedded silver nano particles is described. This biologically active polymer layer was deposited using the plasma polymerization of allyl alcohol. Then, these plasma polymer layers were impregnated with silver ions by dipping into a solution of silver nitrate. Subsequently, Ag+ was reduced by the polymer itself and more completely by dipping into a solution of sodium boron hydride. Addition of O2 gas to the allyl alcohol monomer was used to increase the concentration of O functional groups in the layer and to improve the fixation of homogeneously distributed silver nano-particles. The thus produced films have been reduced growth of gram-negative Escherichia coli by >99%.The morphology of prepared films was studied by Scanning Electron Microscopy and Atomic Force Microscopy. Chemical compositions in the whole layer and on the surface of films were investigated using Fourier transform infrared and X-ray photoelectron spectroscopy, respectively.

Effect of excited nitrogen atoms on inactivation of spore-forming microorganisms in low pressure N2/O2 surface-wave plasma

Using a vacuum ultraviolet (VUV) absorption spectroscopy with a compact low pressure plasma light source, the absolute nitrogen atom density was measured to study its role in the spore inactivation with low pressure N2/O2 gas mixture surface-wave plasmas (SWPs). Self-absorption effect of the resonance emission lines of nitrogen atoms near 120 nm was minimized by optimizing its discharge conditions of the plasma light source. Experimental results showed that excited nitrogen atom densities monotonically decreased with the decrease of N2 gas percentage in N2/O2 gas mixture SWPs, concomitantly with similar decrease of VUV/UV emission intensities of nitrogen atoms and molecules. In the pure N2 gas SWPs, it was confirmed that a dominant lethal factor was VUV/UV emission generated by N2 plasma, while spore etching occurred via physical and chemical interactions with nitrogen species. With an addition of O2 gas, significant spore etching by excited oxygen atoms made it much easier for the VUV/UV photons emitted by nitrogen atoms, N2 and NO molecules to penetrate through the etched spore coats to the core and cause the fatal DNA damage of the microorganisms. As a result, more rapid inactivation was achieved in the middle region of N2/O2 gas mixture ratio, such as 30–80% O2 gas addition, in the present N2/O2 gas mixture SWPs.

Enhanced electrochromic performance of flexible WFexOyCz films by O2 gas addition using low temperature plasma polymerization

An investigation was conducted into the prominent lithium electrochromic performance of flexible organo-tungsten-iron oxide (WFexOyCz) films deposited onto flexible (60 Ω/□ polyethylene terephthalate/indium tin oxide) substrates. The simple one-step low temperature (∼23 °C) plasma polymerization method was used to inject the precursors tungsten hexacarbonyl [W(CO)6] and biscyclopentadienyl iron [Fe(C5H5)2] into the plasma chamber, whilst being mixed with O2 gases at various gas flow rates. The plasma-polymerized WFexOyCz films at a certain addition of oxygen gases achieved outstanding lithium electrochemical reversibility of Li+ ion intercalation and de-intercalation proven by a potential sweep switching between −1 V and 1 V at a scan rate of 50 mV/s in a 1 M LiClO4-propylene carbonate electrolyte. High values for optical transmittance modulation (ΔT) of up to 83.2%, optical density (ΔOD) of up to 1.08 and color efficiency (η) of up to 62.3 cm2/C at a wavelength of 854.9 nm were obtained for the amorphous WFexOyCz films synthesized by the addition of oxygen gases at a flow rate of 17 sccm. The results verified that the proper addition of oxygen gas provides a suitable routine to enhance the electrochromic properties of plasma-polymerized WFexOyCz films.

A Process‐Structure Investigation of Aluminum Oxide and Oxycarbide Thin Films prepared by Direct Liquid Injection CVD of Dimethylaluminum Isopropoxide (DMAI)

AbstractWe present the direct liquid injection CVD of aluminum oxide and oxycarbide thin films using dimethylaluminum isopropoxide at high process temperature (500–700 °C) with the addition of O2 gas, and at low temperature (150–300 °C) with the addition of H2O vapor. Very smooth films with typical roughness values lower than 2 nm are obtained. The thin films are composed of an amorphous material. The composition evolves as a function of temperature from that of a partial hydroxide to a stoichiometric oxide at low deposition temperature (150–300 °C), and from that of a stoichiometric oxide to a mixture of an oxide with an (oxy) carbide at higher temperature (500–700 °C).

Structural and electrical properties of high-k HfO2 films modified by CHF3 and C4F8/O2 plasmas

As-deposited HfO2 films were modified by CHF3, C4F8, and mixed C4F8/O2 plasmas in a dual-frequency capacitively coupled plasma chamber driven by radio frequency generators of 60 MHz as the high frequency (HF) source and 2 MHz as the low frequency source (60/2 MHz). The influences of various surface plasma treatments under CHF3, C4F8, and C4F8/O2 were investigated in order to understand the chemical and structural changes in thin-film systems, as well as their influence on the electrical properties. Fluorine atoms were incorporated into the HfO2 films by either CHF3 or C4F8 plasma treatment; meanwhile, the C/F films were formed on the surface of the HfO2 films. The formation of C/F layers decreased the k value of the gate stacks because of its low dielectric constant. However, the addition of O2 gas in the discharge gases suppressed the formation of C/F layers. After thermal annealing, tetragonal HfO2 phase was investigated in both samples treated with CHF3 and C4F8 plasmas. However, the samples treated with O-rich plasmas showed monoclinic phase, which indicated that the addition of O plasmas could influence the Hf/O ratio of the HfO2 films. The mechanism of the t-HfO2 formation was attributed to oxygen insufficiency generated by the incorporation of F atoms. The capacitors treated with C4F8/O2 plasmas displayed the highest k value, which ascribed that the C/F layers were suppressed and the tetragonal phase of HfO2 was formed. Good electrical properties, especially on the hysteresis voltage and frequency dispersion, were obtained because the bulk traps were passivated by the incorporation of F atoms. However, the H-related traps were generated during the CHF3 plasma treatments, which caused the performance degradation. All the treated samples showed lower leakage current density than the as-deposited HfO2 films at negative bias due to the reduced trap-assisted tunneling by the incorporation of F to block the electrons transferring from metal electrode to the trap level.

Optical and electrical properties of sputter-deposited ZnMgAlO UV-range transparent conducting films

Effects of the Al concentration and the growth variables on the optical and electrical properties of UV-range Zn0.88-xMg0.12AlxO TCO films were studied in detail. As the Al content increased from 0% to 5%, the band gap increased from 3.6 to 3.8 eV, with the optical transmittance maintained at ∼90% within the 370–800 nm wavelength range. The resistivity significantly decreased by doping the film with Al, to 2–3 × 10−3 Ω cm, but was not critically affected by the addition of a larger amount of Al. The resistivity drastically increased with the addition of O2 gas into the Ar sputter plasma and/or by increasing growth temperature. It was proposed that the density of the point defects, as well as the presence of the dopant impurity, plays a key role in determining the carrier concentration. Minimum resistivity, ∼3 × 10−3 Ω cm, was obtained when grown at 10 mTorr pressure, 125 W RF power, Ar ambient and room temperature.

Effect of different sputtering gas mixtures on the structural, electrical, and optical properties of p-type NiO thin films

We investigated how mixtures of Ar and O2 or N2 gases affect the structural, electrical and optical properties of RF-magnetron-sputtered NiO films. It is shown that the addition of O2 gas to Ar ambient (namely, Ar:O2=2:1 to 1:2) slightly reduces the (200) texturing of the NiO films. The introduction of N2 gas (from 0 to 2sccm) to Ar:O2 (2:1) mixture enhances the (200) texturing, while the addition of N2 gas (from 0 to 2sccm) to Ar ambient slightly weakens the (111) texturing. The deposition rate is reduced from 6.1 to 1.5nm/min when O2 gas is added to Ar ambient. The addition of N2 gas to the Ar:O2 (2:1) mixture slightly increases the deposition rate from 1.8 to 2.6nm/min, whereas adding N2 gas to Ar only ambient somewhat reduces the rate from 6.1 to 4.4nm/min. The carrier concentration of the films is increased and the mobility is decreased as the O2 flow rate in the Ar:O2 mixture is increased. The addition of N2 gas to the Ar:O2 (2:1) mixture increases the resistivity of the films, while adding N2 gas to Ar ambient decreases the resistivity. The transmittance and optical bandgap of the films are reduced (from 58.4 to 45.5% at 550nm and from 3.5 to 3.3eV, respectively) with increasing O2 flow to Ar ambient. When N2 gas is added to the Ar:O2 (2:1) mixture, the transmittance in the visible wavelength range increases from 58.4 to 71.3% and the optical bandgap increases from 3.5 to 3.6eV. However, adding N2 gas to the Ar only ambient results in decrease in the transmittance in the visible wavelength region (from 69.3 to 56%) and the optical bandgap (from 3.7 to 3.5eV).

Inductively coupled plasma reactive ion etching of FePt magnetic thin films in a CH4/O2/Ar plasma

An inductively coupled plasma (ICP) reactive ion etching of FePt thin films masked with TiN films was carried out in CH4/O2/Ar plasma. As CH4 gas was added to Ar, the etch rates of the FePt thin films and TiN hard mask decreased gradually, and the etch profile of the FePt films improved slightly. The addition of O2 gas to the CH4/Ar gas mixture enhanced the etch profile due to an increase in the etch selectivity of the FePt film to the TiN hard mask. From optical emission spectroscopy (OES) for the CH4/O2/Ar gas mix, the increase in etch selectivity was attributed to the increase in [H] species as well as [O] species due to the addition of O2 gas.With increasing ICP rf power and dc-bias voltage to the substrate, the etch rates increased and the etch profiles improved with a higher degree of anisotropy. X-ray photoelectron spectroscopy (XPS) of the etched FePt films revealed the existence of Fe-containing compounds formed during etching in CH4/O2/Ar plasma. The etch characteristics, OES and XPS analysis of the film surface showed that the etching of FePt films in CH4/O2/Ar plasma follows mainly sputter etching with the assistance of chemical reactions with the films.

Effect of O2 gas partial pressure on mechanical properties of Al2O3 films deposited by inductively coupled plasma-assisted radio frequency magnetron sputtering

The effect of O2 partial pressure on the mechanical properties of Al2O3 films is studied. Using films prepared by inductively coupled plasma-assisted radio frequency magnetron sputtering, the deposition rate of Al2O3 decreases rapidly when oxygen is added to the argon sputtering gas. The internal stresses in the films are compressive, with magnitude decreasing steeply from 1.6 GPa for films sputtered in pure argon gas to 0.5 GPa for films sputtered in argon gas at an O2 partial pressure of 0.89 × 10−2 Pa. Stress increases gradually with increasing O2 partial pressure. Using a nanoindentation tester with a Berkovich indenter, film hardness was measured to be about 14 GPa for films sputtered in pure argon gas. Hardness decreases rapidly on the addition of O2 gas, but increases when the O2 partial pressure is increased. Adhesion, measured using a Vickers microhardness tester, increases with increasing O2 partial pressure. Electron probe microanalyzer measurements reveal that the argon content of films decreases with increasing O2 partial pressure, whereas the O to Al composition ratio increases from 1.15 for films sputtered in pure argon gas to 1.5 for films sputtered in argon gas at O2 partial pressures over 2.4 × 10−2 Pa. X-ray diffraction measurements reveal that films sputtered in pure argon gas have an amorphous crystal structure, whereas γ-Al2O3 is produced for films sputtered in argon gas with added O2 gas. Atomic force microscopy observations reveal that the surface topography of sputtered Al2O3 films changes from spherical to needlelike as O2 partial pressure is increased. Fracture cross sections of the films observed by scanning electron microscopy reveal that the film morphology exhibits no discernible features at all O2 partial pressures.

High density plasma reactive ion etching of CoFeB magnetic thin films using a CH4/Ar plasma

In this study, high density plasma reactive ion etching of CoFeB magnetic thin films was investigated using CH4/Ar and CH4/O2/Ar gas mixes. The etch rate, etch selectivity and etch profile of CoFeB thin films were obtained as a function of gas concentration and etch parameters. The etch rate of CoFeB thin films and Ti hard mask gradually decreased with increasing CH4 or O2 concentrations. As the CH4 gas was added to Ar gas, the etch profile of the CoFeB thin films improved. The addition of O2 gas into the CH4/Ar gas mix also led to anisotropic etching of the CoFeB thin films. With an increase in the dc-bias voltage supplied to the substrate and a decrease in gas pressure, the etch rates increased and the etch profile became vertical without any redepositions or etch residues. Based on the etch characteristics and surface analysis of the etched films by X-ray photoelectron spectroscopy, it can be concluded that the etch mechanism of CoFeB thin films in CH4/Ar and CH4/O2/Ar plasmas does not follow the reactive ion etch mechanism but rather a chemically assisted physical sputtering mechanism.

Effect of Process Parameters on TSV Formation Using Deep Reactive Ion Etching

In the development of 3D package, through silicon via (TSV) formation technology by using deep reactive ion etching (DRIE) is one of the key processes. We performed the Bosch process, which consists of sequentially alternating the etch and passivation steps using SF6 with O2 and C4F8 plasma, respectively. We investigated the effect of changing variables on vias: the gas flow time, the ratio of O2 gas, source and bias power, and process time. Each parameter plays a critical role in obtaining a specified via profile. Analysis of via profiles shows that the gas flow time is the most critical process parameter. A high source power accelerated more etchant species fluorine ions toward the silicon wafer and improved their directionality. With O2 gas addition, there is an optimized condition to form the desired vertical interconnection. Overall, the etching rate decreased when the process time was longer. (Received May 12, 2010)