Addition Of Oxygen Gas Research Articles

Mechanisms of microexplosion-accelerated pyrolysis and oxidation of lithium-containing droplets: an atomistic perspective.

Microexplosion has been extensively studied in the context of fuel spray and droplet evaporation in engines, while its existence, impact and atomistic insight have rarely been explored in the context of flame synthesis of nanoparticles. In this study, reactive force-field molecular dynamics simulations are performed to elucidate the mechanisms of pyrolysis and oxidation of an isolated lithium nitrate nanodroplet. During the pyrolysis process, the nucleation and growth of a bubble are observed inside the droplet, which should be ascribed to the release of nitrogen and oxygen gases from the decomposition of lithium nitrate, ultimately leading to rapid droplet fragmentation (microexplosion). To demonstrate the role of microexplosion with various intensities, via altering ambient temperature and addition of oxygen gas into the environment, thorough analyses of bond reactions, droplet morphology and compounds of the synthesized lithium nanoparticles are carried out. With elevated ambient temperature, the droplet substantially expands due to bubble growth and the time required for droplet disruption is shortened, which implies the enhanced strength of microexplosion. Simultaneously, the connection between the lithium and other atoms becomes weak, as evidenced by a decrease in the number of lithium bonds. These give rise to a reduction in the quantity of large-sized lithium agglomerates and simultaneously an increase in the amount of fine lithium nanoparticles. To further clarify the reaction mechanism for a lithium-containing droplet under various ambient conditions, three reaction modes, i.e., core-shell diffusion-controlled, microexplosion-accelerated and microexplosion-dominated, are distinguished based on the intensity of microexplosion and the quality of synthesized lithium nanoparticles. Fine lithium-containing nanoparticles are expected to be produced in the microexplosion-dominated mode under high temperature conditions.

High-speed etching of gallium nitride substrate using hydrogen-contained atmospheric-pressure plasma

Atmospheric-pressure plasma etching of a gallium nitride (GaN) substrate using hydrogen radicals instead of chlorine radicals was investigated toward the backside thinning of GaN vertical power devices to reduce on-resistance. As a basic experiment, a pipe-shaped electrode was placed facing the GaN substrate to generate atmospheric-pressure plasma of a gas mixture of helium and hydrogen and high-speed etching of approximately 4 μm min−1 was achieved. Although many spherical Ga metal particles were observed on the surface after processing, the addition of oxygen gas was found to be able to suppress them.

Increased Hydrophilicity of Silicon Surface through Plasma Treatment with Hydrogen Peroxide Gas

Increased Hydrophilicity of Silicon Surface through Plasma Treatment with Hydrogen Peroxide GasSpiegelman, D. Alvarez, C. Ramos (RASIRC), K. Andachi, G. Tsuchibuchi, and K. Suzuki (Taiyo Nippon Sanso Corporation)Wafer bonding is a critical step in the development of advanced semiconductor and MEMS devices.1 Wafer bonding enables the bonding of dissimilar materials as well as the union of separate manufacturing pathways where the pathway steps are dissimilar and frequently incompatible to a single wafer process. Oxide wafer bonding is a common bonding method that requires the wafer surface to have a uniformly flat surface with sufficiently dense hydroxyl (-OH) groups. The hydroxyl groups provide a pathway for chemical covalent bonding between two wafer surfaces (EG Si-O-Si). Ultimately, the wafer bonding strength is a function of the density of the hydroxyl groups populated on the wafer surface before bonding.Several challenges are associated with functionalizing wafer surfaces. Wet Thermal oxidation is a common method for incorporating surface hydroxyl groups on silicon, however this process typically takes place at very high temperatures (>600C °) where surface hydroxyl groups may reversibly desorb, thus limiting surface functionalization. Surface oxidation by Oxygen plasma is another common method for the creation of hydrophilic surfaces,2 however, this property may be attributed to bridging oxides on the surface, where hydroxyl groups may not be present. In the latter case, residual charge or surface radical species may lead to the observed improvement in wafer bonding properties. Plasma oxidation allows for lower temperature activation.2 Oxygen or clean dry air are frequently used in the plasma process with argon.Our investigation involves the use of hydrogen peroxide gas. In recent years this material has become available in the gas phase where:Gas-phase H2O2/H2O mixture is delivered from an ampoule-based formulation. (RASIRC® BRUTE® Peroxide)High concentration H2O2/H2O is vaporized by in situ concentration methods and use of a membrane vaporizer as a gas generator. (RASIRC Peroxidizer®)Early studies by Kummel3 demonstrated that Hydrogen peroxide gas provides a denser hydroxyl surface on SiGe and Ge vs water. Here, all thermal methods were utilized at reduced temperatures.Before our current work, the creation and use of gas-phase hydrogen peroxide plasma has not been addressed. The objective of this work is to demonstrate the generation of hydrogen peroxide plasma and compare its surface functionalization characteristics to those of water and oxygen plasma methods.A constant gas stream of H2O2/H2O mixture in a carrier gas was introduced to a remote plasma source (MKS). (Figure 1). The use of an argon carrier gas led to stable ignition of the plasma mixture. The subsequent addition of oxygen gas gives rise to plasma instability.In the comparative study, the H2O2 gas stream was mixed with water vapor, molecular oxygen, and argon in different ratios, subjected to a remoted plasma. Functionalization was then carried out on a Si-H terminated surface (HF last silicon wafer surface). Thermal effects without plasma were also compared. Surface hydrophilicity (relative Hydroxyl density) was determined by contact angle measurements with the use of a goniometer.The initial wafer surface after HF clean had a water contact angle of 84.9 °. The smallest wetting angle was found for H2O2/H2O/Ar plasma at 4 °. Water alone led to a wetting angle that was 62.5% larger than the hydrogen peroxide mixture. The angle increased with increasing oxygen concentration in the H2O2 gas stream. The wetting angle with dry oxygen at 200C ° was 27.3°. Thermal only H2O2 gas at 150C° was 47.3 ° and further reduced to 11.4 ° when the temperature was increased to 300C °. (Figure 2). These results along with mechanism and ramifications for wafer bonding will be discussed.

Ion formation in an argon and argon-oxygen gas mixture of a magnetron sputtering discharge

Formation of singly and doubly charged Arq+ and Tiq+ (q = 1,2) and of molecular Ar, ArTi+, and Ti ions in a direct current magnetron sputtering discharge with a Ti cathode and argon as working gas was investigated with the help of energy-resolved mass spectrometry. Measured ion energy distributions consist of low-energy and high-energy components resembling different formation processes. Intensities of Ar and ArTi+ dimer ions strongly increase with increasing gas pressure. Addition of oxygen gas leads to the formation of positively charged O+, , and TiO+ and of negatively charged O− and ions.

Flexible electrochromic tungsten/iron mixed oxide films synthesized by an atmospheric pressure plasma jet

Flexible electrochromic organo-tungsten-iron oxide (WFexOyCz) films are rapidly deposited onto flexible (60 Ω/□ polyethylene terephthalate/indium tin oxide; PET/ITO) substrates by a low temperature-atmospheric pressure-plasma polymerization method with an atmospheric pressure plasma jet (APPJ) for a short exposed duration of 48 s. The precursor vapors of tungsten hexacarbonyl [W(CO)6] and biscyclopentadienyl iron [ferrocene; Fe(C5H5)2] are mixed with O2 gases at various gas flow rates, injected into air plasma jet and sprayed onto PET/ITO substrates at room temperature (~23 °C) and at atmospheric pressure (1.013 × 105 Pa). Flexible electrochromic WFexOyCz films are synthesized with a specific addition of oxygen gases with superior lithium electrochromic properties as demonstrated by a potential sweep alternating between −1 V and 2 V at a scan rate of 40 mV/s in a 1 M LiClO4-propylene carbonate electrolyte. With amorphous WFexOyCz films produced with an APPJ by adding oxygen gases at a specific flow rate of 0.5 sccm, a high value in oxygen deficiency up to 0.189 allows more Li+ ions to intercalate into and deintercalate out of the film. Significant coloration and bleaching are proven by the high values in optical transmittance modulation (ΔT) of up to 70.3%, optical density (ΔOD) up to 0.77 and color efficiency (η) up to 61.3 cm2/C, at a wavelength of 800 nm, respectively.

Experimental study on bacteria disinfection using a pulsed cold plasma jet with helium/oxygen mixed gas

Cold atmospheric plasma jet is widely used in many fields due to the reactive oxygen species and low temperature for heat-sensitive products. This paper presents the inactivation of bacteria via a pulsed plasma jet with He/O2 mixed gas. To evaluate the disinfection performance, Staphylococcus aureus was used as an indicator bacteria for experiments. When the plasma jet dealt with agar plates spraying bacteria, it was found that mixed gas has a better performance than pure inert gas, indicated by the disinfection area. The increment of oxygen gas addition was beneficial to the disinfection ability of the plasma jet, while the gas had an opposite effect on the length of jet production. The experiments showed the efficacy of Staphylococcus aureus disinfection could reach up to 99.47% via a helium/oxygen (2%) plasma jet.

Functional interlayers with controlled adhesion developed for polymer composites

The plasma coating of glass fibers is an alternative technology to the wet chemical processes employed for the commercial sizing used for glass-fiber-reinforced polymer composites. A polymer-like film prepared by plasma polymerization can be used as a compatible interlayer between the glass fiber and the polymer matrix. The shear stress distribution across the interphase in a fiber-reinforced polymer composite indicates that the interfacial adhesion at the interlayer/fiber interface is the key factor influencing the performance of the polymer composite. The plasma-polymerized tetravinylsilane deposited at an enhanced effective power was tested as an adhesion film on planar glass substrate using a nanoscratch test. The work of adhesion was used as a measure of film adhesion based on the analysis of the scratch mechanics. An enhanced effective power (0.1–10 W) resulted in a film adhesion change only in the region of 30% for plasma-polymerized tetravinylsilane. The addition of oxygen gas to the tetravinylsilane monomer enabled the depositing of films over a wide range of film adhesions. A 3.7-fold increase in film adhesion was revealed for optimized deposition conditions. For a given film, a strong correlation was found between the shear strength of the polymer composite with glass fibers coated by plasma polymer film and the corresponding film adhesion on planar glass substrate determined using the nanoscratch test.

22.2: Invited Paper: Sputtered Molybdenum‐Oxide for Anti‐Reflection Layers in Displays: Optical Properties and Thermal Stability

Molybdenum (Mo) is commonly used for thin film transistor (TFT) metallization in displays. Apart from its outstanding electronic and adhesive properties in the metallic form, it also possesses stable oxidation states, including sub‐stoichiometric oxides. Depending on the amount of oxygen, the properties can be widely tuned and oxygen‐deficient MoO3‐y films can be electrical conducting and optically absorbing, making them suitable candidates for integration as low‐reflection coatings for on/in cell touch, black matrix on array, narrow bezel, or TFT metallization. Deposition of these oxides by fully reactive sputtering from metal targets implies several problems such as lateral inhomogeneities on large substrates (>G5) and difficult control of oxygen flow. To avoid these obstacles, DC‐ sputtering from ceramic Molybdenum oxide targets without the addition of oxygen gas is proposed.In our work, we show the non‐reactive DC‐sputtering of MoOx:TaOx in a stable and reliable process with deposition rates of up to 180 nm/min. Further on, the electrical, optical, and structural properties of the resulting films are studied. The reflectance of light from external sources and the resulting color impression of the dark layer coatings is investigated on different substrates. The color coordinates of the film can be tuned by the layer thickness, the type of covered metal layer (e.g. Cu, Al, Mo), as well as composition of the oxide. From a process stability point of view, we discuss changes during additional annealing steps, and show structural changes at elevated temperatures.

Influence of Oxygen Gas Ratio on the Properties of Aluminum-Doped Zinc Oxide Films Prepared by Radio Frequency Magnetron Sputtering.

Aluminum-doped zinc oxide (AZO) thin films were deposited on glass and polyimide substrates using radio frequency magnetron sputtering. We investigated the effects of the oxygen gas ratio on the properties of the AZO films for Cu(In,Ga)Se2 thin-film solar cell applications. The structural and optical properties of the AZO thin films were measured using X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), and UV-Visible-NIR spectrophotometry. The oxygen gas ratio played a crucial role in controlling the optical as well as electrical properties of the films. When oxygen gas was added into the film, the surface AZO thin films became smoother and the grains were enlarged while the preferred orientation changed from (0 0 2) to (1 0 0) plane direction of the hexagonal phase. An improvement in the transmittance of the AZO thin films was achieved with the addition of 2.5-% oxygen gas. The electrical resistivity was highly increased even for a small amount of the oxygen gas addition.

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.

Effects of Ga concentration, process conditions, and substrate materials on properties of ZnMgBeGaO ultraviolet-range transparent conducting films

The effects of gallium (Ga) concentration, growth variables and substrate materials on the optical, electrical, and structural properties of the sputter grown Zn0.92-xMg0.05Be0.03GaxO films were studied in detail. The resistivity significantly decreased by doping the film with Ga, from 46.8Ωcm to 1.6×10−3Ωcm, indicating that Ga is an effective donor. It was observed that the crystalline quality of the films degrades, the resistivity increases with increasing growth temperature (Tg), and the resistivity drastically increased with the addition of oxygen gas to the Ar plasma. It was proposed that the Tg effect is mainly due to the increase in the Ga concentration and the oxygen effect is due to the decrease in the point defect density and the passivation of Ga donors. It was also observed that the band gap of the films decreases with increasing Tg and O2 concentration, due to the combined effects of the Burstein–Moss effect and the compositional changes. Films grown on GaN substrates showed significantly improved crystalline quality compared with those of samples grown on Si or SiO2, due to the reduced lattice mismatch.

Rapid destruction of the rhodamine B using TiO2photocatalyst in the liquid phase plasma

BackgroundRhodamine B (RhB) is widely used as a colorant in textiles and food stuffs, and is also a well-known water tracer fluorescent. It is harmful to human beings and animals, and causes irritation of the skin, eyes and respiratory tract. The carcinogenicity, reproductive and developmental toxicity, neurotoxicity and chronic toxicity toward humans and animals have been experimentally proven. RhB cannot be effectively removed by biological treatment due to the slow kinetics. Therefore, RhB is chosen as a model pollutant for liquid phase plasma (LPP) treatment in the present investigation.ResultsThis paper presents experimental results for the bleaching of RhB from aqueous solutions in the presence of TiO2 photocatalyst with LPP system. Properties of generated plasma were investigated by optical emission spectroscopy methods. The results of electrical-discharge degradation of RhB showed that the decomposition rate increased with the applied voltage, pulse width, and frequency. The oxygen gas addition to reactant solution increases the degradation rate by active oxygen species. The RhB decomposition rate was shown to increase with the TiO2 particle dosage.ConclusionThis work presents the conclusions on the photocatalytic oxidation of RhB, as a function of plasma conditions, oxygen gas bubbling as well as TiO2 particle dosage. We knew that using the liquid phase plasma system with TiO2 photocatalyst at high speed we could remove the organic matter in the water.

Effects of oxygen addition on enhancing electrochromic performance of flexible tungsten/tantalum oxide films using an atmospheric pressure plasma jet

An investigation was conducted on the lithium electrochromic performance of flexible organo-tungsten-tantalum oxide (WTaxOyCz) films enhanced by the addition of oxygen gases into an atmospheric pressure plasma jet at various flow rates for a short exposure duration of 33s. The deposition of flexible WTaxOyCz films onto flexible 40Ω/□ polyethylene terephthalate/indium tin oxide substrates using a certain addition of oxygen gas into plasma jet offers notable electrochromic performance after 200cycles of reversible Li+ ion intercalation and de-intercalation in a 1M LiClO4-propylene carbonate electrolyte tested by potential sweep switching between −1V and 1V at a scan rate of 50mV/s and the potential step switching at −1V for 20s and 1V for 13s. The optical modulation (ΔT) of amorphous WTaxOyCz at a wavelength of 803.4nm was significantly improved from 29.8% without the addition of oxygen gas to 61.2% with the addition of oxygen gas at a flow rate of 0.75sccm into a plasma jet.

Efficient Fluorescence “Turn-On” Sensing of Dissolved Oxygen by Electrochemical Switching

We report on a novel method for sensing oxygen that is based on the use of a perylene diimide dye (1) which is electrochemically reduced to its nonfluorescent dianion form (1(2-)). In the presence of oxygen, the dianion is oxidized to its initial form via an electron-transfer reaction with oxygen upon which fluorescence is recovered. As a result, the fluorescence intensity of the dianion solution increases upon the addition of oxygen gas. Results demonstrate that high sensitivity is obtained, and the emission intensity shows a linear correlation with oxygen content (0.0-4.0% v/v) at ambient barometric pressure. In addition, using electrochemical reduction, oxygen determination becomes regenerative, and no significant degradation is observed over several turnovers. The limit of detection is 0.4% oxygen in argon gas.

Design and testing of a novel hypolimnetic oxygenation system to improve water quality in Lake Bard, California

Hypolimnetic oxygenation, the engineered addition of oxygen gas to the bottom of lakes and reservoirs, can improve water quality by repressing the accumulation of nutrients, metals, and toxic compounds in bottom waters. This study designed and tested an oxygenation system in Lake Bard, California. Hypolimnetic oxygen demand, a key design parameter, was estimated through the combination of sediment–water chamber incubations and numerical analysis of water column dissolved oxygen (DO) profiles. Chamber incubations showed that increased water velocity near the sediment–water interface substantially increased the rate of sediment oxygen uptake, and this observation was incorporated into system sizing. The chamber study also confirmed that maintenance of oxygenated conditions repressed sediment release of phosphate, ammonia, manganese, and sulfide. Phosphorus and manganese release rates were 6–8 mg/m2/d and 2–5 mg/m2/d under anoxic conditions, respectively, but negligible or negative under oxic conditions. The novel hypolimnetic oxygenation system used a waste product, oxygen-rich off-gas from an ozone contactor at a nearby water treatment plant, to sustainably improve source water quality. The system was tested over a 2 week period in June 2004. Oxygen addition averaged 380 kg/d and increased bottom water DO from 1–2 to 5–6 mg/L with a concurrent drop in water column phosphate and iron, and a delay in sediment release of ammonia. Manganese, with its slow oxidation kinetics, remained in bottom waters during the oxygenation test, indicating that the oxygenation system needs to be turned on earlier in the season to better control manganese accumulation in bottom waters.

Sputter‐deposited Ga–Sn–Zn–O thin films for transparent thin film transistors

AbstractGa–Sn–Zn–O (GTZO) thin films were prepared on glass substrates at 100 °C by co‐sputtering of Ga‐doped ZnO and SnO2 targets. Characteristic properties of the films were investigated with varying oxygen gas content in the sputtering ambient. Whereas amorphous GTZO films were prepared with pure Ar sputtering, polycrystalline films were obtained with the addition of oxygen gas. With a proper mixing ratio of sputtering gases, O2/(Ar + O2) ∼2%, we could obtain GTZO films with good performances as an active channel material in thin film transistor (TFT); i.e, field effect mobility of 12.2 cm2 V−1 s−1, on/off current ratio of 109, and subthreshold voltage swing of 0.46 V decade−1.

Study on wettability improvement and its uniformity of wool fabric treated by atmospheric pressure plasma jet

AbstractThe influence of processing parameters on wettability improvement and its uniformity of wool fabric treated by atmospheric pressure plasma jet (APPJ) was explored. A woven wool fabric was treated by APPJ under various treatment conditions such as different treatment time, different oxygen flow rate, and different jet‐to‐substrate distance. The water absorption time of wool fabric was measured to determine wettability improvement. The diffusion photo of water droplet on wool fabric surface was taken by digital camera to reflect wettability uniformity. After APPJ treatment, SEM observation showed that the scales on the wool fiber surface directly facing plasma jet pores were destroyed than those on the other fiber surface. XPS analysis showed that the carbon concentration substantially decreased. The concentration of oxygen and nitrogen significantly increased and but the concentration of sulfur and silicon did not obviously changed. With the addition of oxygen gas, more polar groups such as hydroxyl and carboxyl produced on wool fiber surface. The water absorption time of wool fabric greatly reduced indicating wettability improvement. The diffusion of water droplet on wool fabric surface was also larger and more homogenous suggesting uniform plasma treatment. It was concluded that the wettability improvement and its uniformity of the treated wool fabric increased and then decreased with the increasing oxygen flow rate and jet‐to‐substrate distance, and increased with the increasing treatment time. Therefore to achieve reasonable wettability and its uniformity of the wool fabric treated by APPJ, plasma treatment conditions have to be carefully chosen. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Photocurrent and Photoluminescence of Amorphous Silicon Nanoclusters Embedded in Silicon Suboxide Matrix

We have presented a technique, based on magnetron sputtering of silicon target in the mixture of argon, silane, and oxygen. Addition of oxygen gas was shown to cause formation of silicon suboxide layers with amorphous silicon nanoclusters without subsequent annealing. The layers exhibit significant photoluminescence at room temperature. Their photoluminescence spectra reveal special features predicted in the preceding well-known theoretical works. Heterostructures, fabricated with such layers, show high photocurrent efficiency in short-wavelength spectral region. Our results demonstrate that the investigated structures are promising for photoelectric and photovoltaic applications.

The Effect of Microwave-Assisted for Photo-Catalytic Degradation of Rhodamine B in Aqueous Nano TiO2 Particles Dispersions

The photo-catalytic decomposition of rhodamine B was examined in aqueous nano TiO2 particles dispersions to assess effects of the microwave radiation assisted photo-catalytic process driven by UV radiation. The results of photo-catalytic degradation of rhodamine B showed that the decomposition rate increased with the microwave intensity, UV intensity, TiO2 particle dosages and the circulating fluid velocity. Addition of oxygen gas in the photo-catalytic degradation of rhodamine B increased the reaction rate. The effect of addition of H2O2 was not significant when photo-catalysis was used without additional microwave radiation or when microwave was irradiated without the use of photo-catalysts. When H2O2 was added under simultaneous use of photo-catalysis and microwave irradiation, however, considerably higher degradation reaction rates were observed. This study demonstrates that the microwave irradiation can play a very important role in photo-catalytic degradation.

Carbon nanotubes decorated with gold, platinum and rhodium clusters by injection ofcolloidal solutions into the post-discharge of an RF atmospheric plasma

In this paper, we present a new, simple, robust and efficient technique to decoratemulti-wall carbon nanotubes (MWCNT) with metal nanoparticles. As case studies, Au, Ptand Rh nanoparticles are grafted onto MWCNTs by spraying a colloidal solution intothe post-discharge of an atmospheric argon or argon/oxygen RF plasma. Themethod that we introduce here is different from those usually described in theliterature, since the treatment is operated at atmospheric pressure, allowing therealization in only one step of the surface activation and the deposition processes.We demonstrate experimentally that the addition of oxygen gas in the plasmaincreases significantly the amount of grafted metal nanoparticles. Moreover, TEMpictures clearly show that the grafted nanoparticles are well controlled in size.