Oxygen Mixed Gas Research Articles

Structural properties of zinc oxide thin films prepared by r.f. magnetron sputtering

ZnO thin films were deposited on sapphire, glass and silicon substrates by r.f. magnetron sputtering using metallic zinc target. A systematic study has been made of the influence of substrate temperature on the film structural properties. They exhibited a c-axis orientation of below 0.5° full width at half maximum of X-ray rocking curves, an extremely high resistivity of 10 10 Ω cm and an energy gap of 3.3 eV at room temperature. It was found that a substrate temperature of 100 °C and target/substrate distance about 50 mm, very low gas pressures of 3.35×10 −3 Torr in argon and oxygen mixed gas atmosphere giving to ZnO thin films a good homogeneity and a high crystallinity.

Improved Low Resistance Contacts of Ni/Au and Pd/Au to p-Type GaN Using a Cryogenic Treatment

A low resistance Ohmic contact to p-type GaN is essential for reliable operation of electronic and optoelectronic devices. Such contacts have been made using Ni/Au and Pd / Au contacts to p-type Mg-doped GaN (1.41×1017 cm−3) grown by metalorganic chemical vapor deposition ( MOCVD ) on ( 0001 ) sapphire substrates. Thermal evaporation was used for the deposition of those metals followed by annealing at temperatures of 400 ∼ 700 °C in an oxygen and nitrogen mixed gas ambient, then subsequently cooled in liquid nitrogen which reduced the specific contact resistance from the range of 9.46∼2.80×10−2 Ωcm2 to 9.84∼2.65×10−4 Ωcm2 for Ni/Au and from the range of 8.35∼5.01×10−4 Ωcm2 to 3.34∼1.80×10−4 Ωcm2 for Pd/Au. The electrical characteristics for the contacts were examined by the current versus voltage curves and the specific contact resistance was determined by use of the circular transmission line method (c-TLM). The effects of the cryogenic process on improving Ohmic behavior (I-V linearity) and reducing the specific contact resistance will be discussed from a microstructural analysis which reveals the metallurgy of Ohmic contact formation.

Poly(t-butyl-3α-(5-norbornene-2-carbonyloxy)-7α,12α-dihydroxy-5β-cholan-24-oate-co-maleic anhydride) for a 193-nm photoresist

A copolymer of t-butyl-3α-(5-norbornene-2-carbonyloxy)-7α,12α-dihydroxy-5β-cholan-24-oate and maleic anhydride was synthesized as a matrix polymer for ArF excimer laser lithography. The polymer has an excellent transmittance at 193nm and possesses good thermal stability up to 255°C. The resist formulated with the polymer showed better dry-etching resistance than the conventional KrF excimer laser resist for chlorine and oxygen mixed gas. A 0.15μm line and space patterns were obtained at a dose of 18mJcm−2 using an ArF excimer laser stepper.

Effects of annealing in an oxygen ambient on electrical properties of ohmic contacts to p-type GaN

Effects of annealing ambient of an oxygen and nitrogen mixed gas on the electrical properties were studied for Au-based ohmic contacts (NiAu, CoAu, CuAu, PdAu, and PtAu) to p-type GaN. Addition of oxygen to the nitrogen gas reduced the specific contact resistances (ρc) and resitivities of the p-GaN epilayers (ρs) of the contacts after annealing at temperatures of 500–600°C. The microstructural analysis at the p-GaN/metal interfaces did not detect the heterostructural intermediate semiconductor layer at the GaN/metal interfaces. The reason for reduction of both the ρc and ρs values by the oxygen gas addition was believed to be due to formation of the p-GaN epilayer with high hole concentrations, caused by removal of hydrogen atoms which bonded with Mg atoms.

Improved Low Resistance Contacts of Ni/Au and Pd/Au to P-Type GaN Using a Cryogenic Treatment

AbstractA low resistance Ohmic contact to p-type GaN is essential for reliable operation of electronic and optoelectronic devices. Such contacts have been made using Ni/Au and Pd / Au contacts to p-type Mg-doped GaN (1.41×1017 cm−3) grown by metalorganic chemical vapor deposition ( MOCVD ) on ( 0001 ) sapphire substrates. Thermal evaporation was used for the deposition of those metals followed by annealing at temperatures of 400 ∼ 700 °C in an oxygen and nitrogen mixed gas ambient, then subsequently cooled in liquid nitrogen which reduced the specific contact resistance from the range of 9.46∼2.80×10−2 ωcm2 to 9.84∼2.65×10−4 ωcm2 for Ni/Au and from the range of 8.35∼5.01×10−4 ωcm2 to 3.34∼1.80×10−4 ωcm2 for Pd/Au. The electrical characteristics for the contacts were examined by the current versus voltage curves and the specific contact resistance was determined by use of the circular transmission line method (c-TLM). The effects of the cryogenic process on improving Ohmic behavior (I-V linearity) and reducing the specific contact resistance will be discussed from a microstructural analysis which reveals the metallurgy of Ohmic contact formation.

Crystal growth of superconductive PrBa 2Cu 3O 7− y

Superconductive PrBa 2Cu 3O 7− y (Pr123) crystals have been grown successfully by the travelling-solvent floating-zone (TSFZ) method using 3.7–5.8% PrO, 27–37% BaO, and 60–69% CuO composition solution with the 0.1–0.4% oxygen mixed argon gas atmosphere. The grown crystals have been identified to be Pr123 by a precession camera, X-ray powder diffractions and scanning electron microscopy–X-ray energy dispersion spectroscopy (SEM-EDS). Some portion of the grown TSFZ crystal boules show bulk superconductivity below about 80 K after annealing in oxygen.

NdBa 2Cu 3O 7-δ superconducting thin films made by the PLD method

We have made NdBa 2Cu 3O 7-δ (NBCO) thin films on (100) SrTiO 3(STO) substrates by the pulsed laser deposition (PLD) method. We have found the optimum deposition conditions in the mixed gas of oxygen and argon as well as in pure oxygen. The NBCO thin films of T c= 93 ∼ 93.5K were obtained, and they were grown epitaxially with c-axis preferred orientation. The critical current density of the NBCO thin films were 1 ∼ 2 × 10 6A/cm 2 at 77 K.

High-deposition-rate growth of PZT thin films by reactive electron beam coevaporation using Ti/Zr alloy

Abstract Lead zirconate titanate (PZT) thin films were prepared by coevaporation of titanium/zirconium alloy and lead metal with an electron beam gun. Each of evaporation rates was independently controlled by each quartz crystal thickness monitor. Titanium/zirconium alloy was used because of simplicity of chemical composition control. To promote oxidation of the films, a mixed gas of oxygen and ozone (5%) was used. When evaporation rates of titanium/zirconium alloy and lead metal were controlled moderately, perovskite phase PZT film was obtained on 50 nm-thick-PbTiO3-film at substrate temperature of 550°C. When atomic ratio of titanium/zirconium alloy was 50:50, chemical composition of the films was Ti:Zr = 9:1. Deposition rate was greater than 50 nm/min, which was much larger than that by the sputtering method.

Magnetic properties of amorphous-like oxides of the Bi 2O 3-Fe 2O 3-PbTiO 3 system synthesized by sol-gel method

Similar to films rf-sputtered in an argon and oxygen mixed gas, amorphous-like oxides (films and powders) with the ternary Bi 2O 3-Fe 2O 3-PbTiO 3 system prepared by sol-gel method develop a considerably large spontaneous magnetization after being annealed above T a = 500 °C in air. The magnetization of gel-coated films showed a sharp maximum I S exceeding 0.1 T in a narrow region with the Fe 2O 3-rich compositions when annealed around T a = 700 °C, where samples showed halo-patterns in X-ray diffraction, retaining the amorphous state, while further increase in Ta results in a rapid decrease in magnetization, where X-ray diffraction lines assigned to para- and/or antiferromagnetic oxide precipitates such as α-Fe 2O 3, BiFeO 3, and Bi 2Fe 4O 9, were apparent. It may be concluded that spontaneous magnetization arises from nano-ferrimagnetic clusters which cannot be detected by X-ray diffraction. In order to elucidate its microscopic origin, Mössbauer measurement was also carried out.

High-Deposition-Rate Growth of Lead Titanate Zirconate Films by Reactive Electron Beam Coevaporation

Lead titanate zirconate (PZT) thin films were prepared by reactive coevaporation of lead, zirconium and titanium with an electron beam gun. To promote oxygenation of deposited films, mixed gas of oxygen and ozone was used. A PZT film with a single perovskite phase was obtained at a substrate temperature of 550° C without post-thermal annealing on a lead titanate film. The deposition rate was 50 nm/min, which was much higher than that in the case of the sputtering method. The axial ratio (c/a) of the tetragonal perovskite phase decreased with the increase of zirconium content.

Direct analysis of materials using direct sample insertion devices and mixed gas inductively coupled plasma atomic emission spectrometry

It is shown that a direct sample insertion (DSI) device can be used in conjunction with inductively coupled plasma atomic emission spectrometry for the direct determination of trace elements in a variety of materials. The majority of analyses involving DSI devices have concerned samples in the form of small aqueous solution volumes or dried solution residues. Successful analyses have now been carried out for the direct insertion of Al2O3, Al metal, oil and botanical samples. The key operational feature that has allowed the successful direct determination of trace elements in these materials, with essentially no a priori sample treatment, is the utilization of an argon–oxygen mixed gas plasma. The calibration curves are linear over a dynamic range of 3–4 orders of magnitude and the detection limits are in the range of tens of picograms.

Strengthening of CFRC by Plasma Treatment with Mixed Gas of Oxygen and CF4

Surface modification of PAN based carbon fiber (CF) was carried out by plasma treatment to obtain high compatibility between CF and matrix in CF paper/cement composites (CFRC). The plasma was generated by radio frequency discharge (13.56MHz) with O2 gas, CF4 gas, and the mixture of two gas.Wettability of CF surface to water was remarkably modified to be hydrophilic for flow ratio of 1.0 (O2 gas only) and 0.75 (O2/CF4=37.5sccm/12.5sccm) of mixed gas, and to be hydrophobic for flow ratio of 0 (CF4 gas only) and 0.25 (O2/CF4=12.5sccm/37.5sccm), while little modification was observed for flow ratio of 0.5 (O2/CF4=25sccm/25sccm).CF papers thus treated were used for the preparation of CFRC. CFRC plates (6mm thick) were prepared by laminating 11 sheets of CF paper preimpregnated with portland cement paste (water/cement 0.4), and curing it in water. These CFRC's bulk density showed the values of 1.39g/cm3 and CF content was 2.7vol%.The flexural strength and Young's modulus of CFRC plates could be controlled by regulating plasma treatment condition (discharge power, kind of gas, flow ratio of mixed gas). The flexural strength of CFRC plate prepared from plasma-treated CF with power of 50W and flow ratio of 0.75 (O2/CF4=37.5sccm/12.5sccm), was about 1.5 times (45MPa) that of CFRC plate prepared from non-plasma treated CF. CFRC plate prepared from CF paper pretreated with power of 150W and flow ratio of 0.75, has a flexural strength 2/3 times (18MPa) that of CFRC from plasma-untreated CF.These experimental results showed that flexural strength of CFRC plate prepared from plasma treated CF paper is affected by kind of gas, flow ratio of mixed gas, and discharge power of plasma.

TfP205. Preparation of lead titanate thin films by reactive electron beam coevaporation using ozone

Abstract Lead titanate(PbTiO3) thin films were prepared by reactive coevaporation of lead and titanium with an electron beam gun. Each of evaporation rates of lead and titanium was independently controlled by each quartz crystal thickness monitor. To promote oxidation of deposited films, a mixed gas of oxygen and ozone was used. When the ratio of lead to titanium was controlled properly, perovskite phase PbTiO3 was obtained at substrate temperature of 550°C without post thermal annealing on glass substrates. The deposition rate was 110nm/min, which was larger than that of prepared by sputtering method and that of prepared by coevaporation without ozone. The ratio of lead to titanium of the perovskite phase films was nearly equal to that of standard PbTiO3 powder sample. The film prepared without post thermal annealing had a smooth surface and was transparent in the visible region.

ANP Decreases Arterial Oxygen Partial Pressure by Increasing Shunt Flow in Pulmonary Circulation.

This study was designed to clarify the decreased arterial oxygen partial pressure (PaO2) mechanism induced by atrial natriuretic peptide (ANP) infusion. In order to examine the effects of ANP on gas exchange across the normal lungs, ANP was infused to eight anesthetized dogs, ventilated with mixed gases of oxygen and nitrogen. PaO2 and venous oxygen partial pressure (PvO2), ventilation-perfusion ratio (VA/Q), shunt-total blood flow ratio (QS/QT) were measured before and during ANP infusion under ventilation with 10, 20, 30% oxygen. In this study ANP decreased PaO2 from 89.0 +/- 4.2 to 85.4 +/- 5.4 mmHg during 20% oxygen ventilation, and from 138.1 +/- 3.6 to 132.5 +/- 4.1 mmHg during 30% oxygen ventilation. ANP increased VA/Q and QS/QT. We conclude that the decrease in PaO2 caused by ANP infusion was mainly due to the increased venous admixture.

Aerobic oxidative-carbonylation of olefins. A convenient preparation of β-hydroxyalkanoic acid derivatives from olefins

A variety of β-hydroxyalkanoic acid derivatives were prepared by palladium catalyzed aerobic oxidative-carbonylations of terminal olefins at normal pressure of carbon monoxide and oxygen mixed gas.

溶鉄および溶鋼の脱窒反応に関する研究

Kinetics of nitrogen desorption reaction of liquid iron and steel has been investigated by means of blowing various gas on the surface of the melt.The nitrogen desorption reaction of liquid iron is of second order, and the reaction rate is remarkably affected by oxygen content in liquid iron.The rate constant decreases in inverse proportion to the second power of oxygen content above 0.03%, increases gradually below this value of oxygen content and tends to approach a constant value below 0.01% of oxygen.From the standpoint of chemisorption of nitrogen atoms on the surface of liquid iron, these results lead to the conclusion that the rate-controlling step is the reaction between these atoms, which is disturbed by adsorbed oxygen atoms.The activation energy of nitrogen desorption reaction is 39 kcal/mole in liquid iron containing oxygen less than 001%.When the decarburization and the nitrogen desorption reactions proceed simultaneously by blowing argon and oxygen mixed gas to liquid steel, the latter reaction is deviated from the second order, and its rate becomes considerably slow in comparison with that of liquid iron by blowing only argon. These facts are considered to be caused by the disturbance of the reaction of nitrogen atoms by the oxygen atoms adsorbed on the surface of liquid steel.