Addition Of O2 Gas Research Articles

Photo-catalytic degradation of rhodamine B using microwave powered electrodeless discharge lamp

A microwave discharge electrodeless lamp (MDEL) was used as the light source for microwave assisted TiO2 photo-catalysis to degrade rhodamine B. A MDEL filled with low pressure mercury gas has been developed for the photo-catalytic treatment of water pollutants over TiO2 balls. TiO2 balls produced by the chemical vapor deposition method were used. The degradation reaction rate was shown to be higher with higher microwave intensity and with a larger amount of O2 gas addition. The effect of addition of H2O2 was not significant when photo-catalysis was used without additional microwave irradiation 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 result suggests that there is a synergy effect when the constituent tech- niques are applied together.

(100) Oriented Sputter-deposited Pt Thin Films on MgO/Fe Composite Bilayers using SiO2/Si substrates With Addition of O2 During Pt Sputtering

AbstractPerovskite type oxide thin films have attracted a lot of attention, because they are essential materials which will be used for various electric devices such as ferroelectric random access memory (FeRAM) and tunable filter devices. When the materials are used for such capacitive devices, bottom electrode layers for oxide films are very important, since they significantly affect the crystallinity of the oxide films. Platinum (Pt) is one of the well known bottom electrode materials used for the oxide thin films. Pt provides also better nucleation sites for such perovskite materials due to small lattice misfit. Since dielectric properties of ferroelectric films are originated from the displacement of ions in a crystal along the c-axis direction, c-axis oriented ferroelectric thin films are required to attain better dielectric properties. (100) oriented Pt layers are required to attain c-axis oriented perovskite type ferroelectric films. In our previous report, we succeeded in preparing (100)-oriented Pt thin films with thickness of 20 nm on SiO2/Si substrate at substrate temperature Ts above 400 °C using MgO (100) buffer layers which deposited on Fe (100) seed layers. However, the growth of Pt(111) texture appeared when the thickness was increased from 20 nm to 100 nm, since (100) texture has relatively higher surface energy than (111) closely packed texture for Pt surface. It suggested that surface energy of the films changed during the deposition. In order to keep the surface energy, addition of O2 gas was performed during Pt deposition. Pt thin films with (100) preferred orientation with thickness above 100 nm were deposited on the (100) oriented MgO layer prepared on very thin seed Fe layers deposited on SiO2/Si substrates at Ts of 500 °C by facing-targets sputtering. It was also succeeded to attain (100) oriented perovskite oxide layer when they were deposited on the Pt(100)/Mg(100)/Fe/SiO2/Si underlayer.

Initial growth process of carbon nanowalls synthesized by radical injection plasma-enhanced chemical vapor deposition

We synthesized carbon nanowalls (CNWs) using radical injection plasma-enhanced chemical vapor deposition. The initial growth process of CNWs was investigated with and without O2 gas addition to a C2F6 capacitively coupled plasma with H radical injection. In the case of the CNW synthesis without the addition of O2 gas, scanning electron microscopy (SEM), transmission electron microscopy, x-ray photoelectron spectroscopy (XPS), and Raman spectroscopy revealed that a 10-nm-thick interface layer composed of nanoislands was formed on a Si substrate approximately 1 min prior to CNW formation. In contrast, with O2 gas addition, SEM and XPS revealed that an interface layer was not formed and that CNWs were grown directly from nanoislands. Moreover, Raman spectroscopy suggested that the interface layer was composed of amorphous carbon and that O2 gas addition during CNW growth is effective for achieving a high graphitization of CNWs. Therefore, O2 gas addition has the effect of reducing the amorphicity and disorder of CNWs and controlling CNW nucleation.

Effect of Surface Treatment on the Mechanical Strength of Ultrasonically Bonded Chip on Copper-Coated Glass for Ultra-Fine Pitch Application in Microelectronics

This study was focused on the effect of surface treatment on the mechanical strength of ultrasonically bonded copper chips on copper-coated glass. The plasma treatment was performed with two different gases, either N2+O2, or N2+H2, for treatment times up to 18 s. Wet treatment was also carried out with 5 vol % H2SO4. Surface analysis was carried out after the treatment using Auger electron spectroscopy (AES) and it was found that treatment conditions greatly affected the joint strength. Wet cleaning with 5 vol % H2SO4 effectively removed oxides from the Cu surface, while addition of O2 gas into N2 gas plasma was good for removing carbides. The treatment conditions greatly affected the removal of contaminants on the Cu surface and the bondability between Cu bumps and Cu-coated glass substrates.

Effect of O2 Gas during Inductively Coupled O2/Cl2 Plasma Etching of Mo and HfO2 for Gate Stack Patterning

In this study, we investigated the etching characteristics of Mo and HfO2 single layers and Mo/HfO2 stacked structure for metal electrode/high-k gate stack patterning in O2/Cl2 inductively coupled plasmas and the effects of O2 addition on the etch rates and etch selectivity of the Mo to the HfO2 layer. By controlling the process parameters such as the O2/Cl2 flow ratio, the top electrode power and the dc self-bias voltage (Vdc), the Mo/HfO2 etch selectivity as high as \\cong67 could be obtained. Addition of O2 gas to the O2/Cl2 chemistry improved the Mo/HfO2 etch selectivity because the O2 gas in a certain flow ratio range reduced the HfO2 etching reactions due to less chlorination of Hf but enhanced the Mo etch rate presumably due to effective formation of highly volatile Mo–O–Cl etch by-products.

Effects of Oxygen Addition on Superconductivity of Sn Cluster-Assembled Films

Sn cluster-assembled films have been produced using a plasma-gas-condensation cluster deposition apparatus with and without O2 gas addition in a sputtering chamber. The Sn clusters prepared without O2 gas addition agglomerated on the substrate and formed larger islands. They exhibited a broad superconducting transition below 3.7 K, suggesting that their transition temperature Tc depends on their cluster size. When O2 gas was added to the cluster source, cluster size decreased and the agglomeration was prevented. The Sn cluster-assembled film prepared at an O2 gas flow rate RO2 =0.05 sccm showed a sharp superconducting transition at Tc=4.0 K, which was higher than the Tc of bulk β-Sn (Tcb=3.7 K). Magnetization measurements indicated that the Sn cluster-assembled films prepared at RO2 ≤0.1 sccm were type II superconductors.

LCD Glass Cleaning by Atmospheric Pressure Glow Discharge Plasma

We report on a novel method for the surface modification of indium tin oxide (ITO) in LCD glass by direct exposure to a dielectric barrier discharge (DBD) at atmospheric pressure and room temperature. To remove the organic contaminants from the surfaces of ITO film in LCD glass, the atmospheric pressure RF glow discharge plasma was used. Argon (Ar) and oxygen (O2) were used as the carrier gas and reactive gas, respectively. The addition of O2 gas to Ar decreased the contact angle of water and increased the surface cleaning rate due to the increase of oxygen radicals in the plasma. The chemical characteristics of ITO surface after the plama treatment were investigated using X-ray photoelectron spectroscopy (XPS), and new carboxyl group bond was produced. The contact angle of 64° before the plasma treatment was decreased to 7° in the processing condition with oxygen flow rate of 50 sccm, treatment speed of 100mm/sec, and input power of 300W. These hydrophilic effect will be very useful in the manufacturing processes of LCD glass.

Metal Leadframe Surface Cleaning Prior to Electroplating by Atmospheric Pressure Glow Discharge Plasma

Metal leadframes (Alloy 42) were cleaned using atmospheric pressure glow discharge plasma. Atmospheric pressure glow plasma was generated by a RF source of 13.56MHz with a matching network (300W power) on to the leadframes free from streamers and arc. Argon (Ar) and oxygen (O2) were used as the carrier gas and reactive gas, respectively. The addition of O2 gas to Ar decreased the contact angle of water and increased the surface cleaning rate due to the ncrease of oxygen radicals in the plasma. The chemical characteristics and morphologies of leadframe surface after the plama treatment were analyzed using X-ray photoelectron spectroscopy (XPS) and atomic force microscope (AFM), respectively. The contact angle of 82° before the plasma treatment was decreased to 5° in the processing condition with oxygen flow rate of 50sccm, treatment speed of 100mm/sec, and input power of 300W. These surface cleaning effect will be very useful in the replacement many steps of wet cleaning before electroplating.

Fabrication and Characterization of Pb(Zr,Ti)O3 Microcantilever for Resonance Sensors

A microcantilever beam that includes the Pb(Zr,Ti)O3 (PZT) layer was fabricated. In this cantilever structure, RuO2 conductive oxide thin film was adopted to simplify the structure. Deposition parameters for PZT film were optimized and the etching conditions of Si were studied. From the hysteresis loop of PZT thin film, we found that the remanent polarization (Pr) of PZT thin film increased as the deposition temperature decreased and the post-annealing temperature increased. When the PZT thin films were deposited at 375°C by the radio frequency (RF) magnetron sputtering method and were annealed at 725°C by a rapid thermal annealing (RTA) process, the Pr of PZT thin film reached the maximum value of 11 µC/cm2. The mode of Si etching changed from isotropic one to anisotropic one with the addition of O2 gas in SF6 gas. Using these optimized conditions, 50 µm wide microcantilevers with different lengths from 50 µm to 150 µm were fabricated. It turned out that the measured resonance frequency ranged from 41.6 kHz to 180 kHz and the resonance frequency decreased as the length of cantilever increased.

Ｎｉ‐Ｃｒ系酸化物薄膜の微細構造に及ぼす酸素添加の影響

Ni-Cr oxide thin films were prepared by the magnetron sputtering with an NiO-Cr2O3 composite target and O2-added Ar sputtering gas. The electric conductivity of the films showed sharp changes from 10-11 S·m-1 to 100 S·m-1 with the addition of O2 gas from 0 vol% to 20 vol%. The existence of the cubic nickel oxide crystal was assured only in the films prepared by the O2-addition of 20 vol% or less from X-ray diffraction measurements. X-ray photoelectron spectroscopic analysis revealed that the chemical states of chromium and nickel are Cr2O3 and Ni1-xO (0<x<0.34), respectively, and the nickel deficiency maybe increased with the addition of O2 gas. These results suggested that the Ni1-xO crystalline particles were embedded in the amorphous Cr2O3 matrix. The crystallite size of Ni1-xO particles increased from 6.3 nm to 32 nm with increase in the O2-addition ratio from 0 vol% to 20 vol%. The close relationship between the electrical conductivity and the Ni1-xO particle size of the films brought us to the conclusion that the increase in conductivity was possibly attributable to the crystal growth of the conductive Ni1-xO crystallites as well as its nickel deficiency.

Modeling of Dielectric Barrier Discharges in Xe/O2 Gas Mixture Influence of O2 Gas Addition on Xe Barrier Discharge Properties

The influence of O2 gas addition (˜1%) on discharge properties of high-pressure Xe dielectric barrier discharges was investigated using one-dimensional fluid model. In calculated voltage-current characteristics, sharp and shallow current pulses were observed during a half cycle in pure xenon case. With an increase in the mixture ratio rO2 of oxygen, only a sharp current pulse was observed. The electronegativity in a discharge gap, which depends on rO2, was varied spatially and temporally. Even in rO2=1%, the maximum of electronegativity was reached to 53.1 at the phase of maximum value of discharge gap voltage. Despite of small rO2, dominant positive and negative charged species were changed from Xe2+ ions and electrons to O2+ and O- ions rapidly.

Specific activity of [11C]CO2 generated in a N2 gas target: effect of irradiation dose, irradiation history, oxygen content and beam energy

Pure and O2-mixed nitrogen gases were irradiated by 18 MeV protons (14.2 MeV on target) and analyzed directly by a specially designed radio-GC system with a FID coupled to a methanyzer. Non-radioactive carbon, especially CO2 was observed to be generated in the target chamber by irradiation and to decrease gradually with repeated irradiation. The amount of carbon was increased by the use of new materials for the front foil, transport line, and so on. Higher irradiation dose also increased the carrier carbon, where beam current affected carbon generation more strongly than irradiation time. The addition of oxygen gas to nitrogen gas also increased the amount of carrier carbon, nearly all of which was observed to be generated in the chemical form of CO2. The ratio of [11C]CO2 to total C-11 was always low in a pure N2 gas target and increased with higher irradiation dose, addition of oxygen gas and by changing some part of the irradiation system. The ratios of [11C]CO2 were 22.4±1.5%, 77.8±7.1% and 94.0±4.0% in a pure N2 gas, 9.8 ppm O2-mixed N2 gas and 2000 ppm O2-mixed N2 gas, respectively. The specific activity of [11C]CO2 increased by the addition of O2 gas, but the effect of irradiation dose was not clear. Maximal specific activity of 610±150 GBq/μmol was obtained at the irradiation condition of 15 μA and 20 minutes in a 2000 ppm O2-mixed N2 gas. The effect of proton energy on the CO2 generation was also examined by degrading the proton energy with different thick energy absorbers. The amount of CO2 generated in the target depended on the proton energy, i.e., larger amount of CO2 generated with higher proton energy. Surprisingly, some amount of CO2 (1.5±0.3 nmol) was still observed in the target, even in the condition that all the protons stopped in the front foil and did not irradiate the target gas.

Effects of Oxygen Gas Addition and Substrate Cooling on Preparation of Amorphous Carbon Nitride Films by Magnetron Sputtering

Amorphous carbon nitride (a-C1-xNx) films were prepared by magnetron sputtering using nitrogen (N2) and oxygen (O2) gases in order to reduce the sp2 structural region and to reduce triple bonding between carbon and nitrogen atoms (C≡N) with oxygen radical. Furthermore, these films were prepared at liquid-nitrogen temperature in order to increase the nitrogen concentration. Electron spin resonance (ESR), infrared (IR) absorption, ultra-violet visual (UV-vis) spectroscopy and X-ray photoelectron spectroscopy (XPS) were used to investigate the effects of O2 gas addition and substrate cooling on the preparation of a-C1-xNx films by magnetron sputtering.

Perfect selective and highly anisotropic electron cyclotron resonance plasma etching for WSix/poly-Si at electron cyclotron resonance position

Perfect selective and highly anisotropic etching for tungsten polycide (WSix/poly-Si) structure without sidewall protection is achieved at the electron cyclotron resonance (ECR) position in a newly developed ECR plasma etching system. The etching selectivity ratio of WSix/poly-Si structure etching to SiO2 etching is infinite by using Cl2/SF6/O2 gas mixture under 5×10−4 Torr. The etching rate is more than 2000 Å/min with no radio frequency bias above selectivity conditions. The addition of a small amount of SF6 is efficient for removing tungsten residue. The perfect etching selectivity is caused by low ion energy at the ECR position and the effect of O2 gas addition. The high etching rate is achieved by high ion current density at the ECR position. Furthermore, a highly anisotropic etching profile is realized at the substrate temperature of 60 °C.

Formation of adsorbed oxide (O2-) and hydroxide on a silver electrode in dilute chromate (CrO42-) electrolytes

Abstract : Surface enhanced Raman scattering has been used to detect in situ the formation of O= and OH- adsorbed on a Ag electrode in an aqueous solution of 25 micromolar Na2Cr2O7 and .01 to .001 M KC1. Both oxide and hydroxide adsorbates are observed after completion of an oxidation-reduction cycle in a standard voltammetry experiment. As the Ag electrode voltage is swept cathodically, the O=ads is protonated to form more OH-ads but, unlike in MnO4- solutions, no further protonation to form H20 occurs at any cell voltage. The addition of O2 gas to the electrolyte deprotonates the adsorbed OH- to form an oxide covered surface. These results for CrO4 solutions are contrasted with previous results for MnO4 electrolytes to obtain information about the nature of the metal-solution interface in chromate passivated metal surfaces. Keywords: Catalysis, Passivation, Metal surfaces, Protonation, Metal oxide absorbates, Silver, Electrodes, Hydroxides.

Laser-induced fluorescence study of silicon etching process: Detection of SiF2 and CF2 radicals

Using a laser-induced fluorescence (LIF) technique, SiF2 and CF2 radicals are detected during the downstream etching of silicon with a discharge of CF4 gas. It is confirmed that SiF2 radical is desorbed from the surface in the etching of silicon by fluorine atom. Addition of O2 gas to the CF4 discharge enhances the LIF intensity of SiF2 radical and extinguishes that of CF2. Mechanism of the increase of etching rate of silicon by addition of O2 is discussed on the basis of the results of LIF measurements. The etching rate of silicon is proportional to the LIF intensity of SiF2, when the microwave power of the discharge is changed. The relationship between the intensity of chemiluminescent continuum and the concentration of SiF2 is revealed, which suggests that the chemiluminescence is attributed to the emission of SiF*3 which is produced by the reaction between SiF2 and fluorine atoms in the gas phase. There is no signal of SiF2 during the etching of either SiO2 or SiNx.

ロックビット用超硬合金の塩化による回収

Some fundamental researches and their industrial applications were done on the chlorination process to recover W and Co from WC-Cosintered hard metals.Carbon in WC-Co alloys (Co10%) exists about 5.6% wt. and can be used as an available heat source by the addition of O2 gas. This fact brought the economical chlorination furnace without external heating to success.Chlorination of WC-Co alloys should be done under the temperature of 850-1, 000°C, under the gasflows of Cl2 and O2 necessary to convert WC-Co to WO2Cl2, CO2 and CoCl2. Reaction velocity was about 3g/cm2. hr at our 40mmφ testing furnace.Industrial tests were done at temperature of 850-1, 000°C, Cl2 and O2 gas flow of each 50l/mininour 300mmφ400mm ht (charging space) testing furnace. About 1 ton alloys were charged, 642kg alloys (corresponding 963kg as chlorides) were reacted for 60hrs and 923kg chlorides were caught. Meanchlorination velocity of WC-Co alloys at our pilot plant was 11.7kg/hr, while our expecting value was 15kg/hr.