• Korean Journal of Optics and Photonics
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• v.18 no.2
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• pp.171-177
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• 2007

We prepared $TiO_2$ thin films by electron-beam evaporation at various oxygen pressures, and investigated their optical and structural properties as a function of the annealing temperature. The physical properties of the $TiO_2$ thin films depend upon the injection oxygen content. With the increased injection of oxygen, the phase transformation temperature and the transmittance of $TiO_2$ thin films in the range of visible wavelength were increased. For low injection of oxygen, the absorption edges of $TiO_2$ thin films were more red-shifted when annealed at temperatures from $700^{\circ}C$ to $1100^{\circ}C$.

• Journal of the Korean institute of surface engineering
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• v.42 no.5
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• pp.220-226
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• 2009

Cr-O-N coatings having different oxygen contents were deposited on Si wafer and SUS 304 substrates by an arc ion plating technique using Cr target in $Ar/O_2/N_2$ gaseous atmosphere. As increasing oxygen content in the coating, the microstructure of Cr-O-N coating changed from polycrystalline having NaCl structure to amorphous structure. Further increase of oxygen content resulted in phase transformation from amorphous to rhombohedral structure. From the variations of d value and average grain size, it was revealed that the maximum solubility of oxygen in Cr-O-N coating was about 21 at.%. And the maximum micro-hardness of 2751HK was obtained in this composition. The lowest friction coefficient was measured in the coating having 34.8 at.% of oxygen. However, more narrow width of wear track was found in the coating having 30.1 at.% of oxygen.

• Journal of the Korean Chemical Society
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• v.28 no.2
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• pp.114-120
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• 1984

The reversible oxygenation of a solid stae polymeric cobalt(II) porphyrin complex, PVP-CoTPP was studied at 0, -24 and $-78^{\circ}C$. When PVP-CoTPP was contacted with $O_2 $at$-78^{\circ}C$ the oxygen uptake increased with oxygen partial pressure. At about 700mmHg $O_2$, the amount of oxygen taken up corresponded approximately one oxygen molecule to one Co(II) complex. The amount of $O_2$ taken up by PVP-CoTPP decreased with increasing temperature. When $16O_2$ was admitted to the Co(II) complex a EPR signal corresponding to $O_2^-$ increased with a decrease in Co(II) signal. The results suggest that an electron is transfered from Co(II) in PVP-CoTPP to oxygen forming a $Co(III)-O_2^-$ complex where $O_2^- $is superoxide type.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.378.1-378.1
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• 2014

In this study, we investigated that the resistance switching characteristics of Nb-doped HfO2 films with increasing Nb doping concentration. The Nb-doped HfO2 based ReRAM devices with a TiN/Nb-doped HfO2/Pt/Ti/SiO2 were fabricated on Si substrates. The Nb-doped HfO2 films were deposited by reactive dc magnetron co-sputtering at $300^{\circ}C$ and oxygen partial ratio of 60% (Ar: 16sccm, O2: 24sccm). Microstructure of Nb-doped HfO2 films and atomic concentration were investigated by XRD, TEM, and XPS, respectively. The Nb-doped HfO2 films showed set/reset resistance switching behavior at various Nb doping concentrations. The process voltage of forming/set is decreased and whereas the initial current level is increased in doped HfO2 films. However, the switching properties of Nb-doped HfO2 were changed above the specific doping concentration of Nb. The change of resistance switching behavior depending on doping concentration was discussed in terms of concentration of non-lattice oxygen and micro-structure of Nb-doped HfO2.

• The Korean Journal of Ceramics
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• v.1 no.1
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• pp.21-28
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• 1995

Electrical conductivity of $TiO_2$ thin films, deposited on $Al_2O_3$ substrates by metal organic chemical vapor deposition (MOCVD), was measured by four-point probe method in a temperature range from $800^{\circ}C$ to $1025^{\circ}C$ and an oxygen partial pressure range from $2.7{\times}10^{-5}$ atm to 1 atm. In the low oxygen partial pressure region n-type conduction was dominant, but in the high oxygen partial pressure region p-type conduction behavior appeared due to substitution of Ti ions by Al ions, which were diffused from the substrate during post deposition annealing process. Electrical conductivity of the film decreases in the n-type region and increases in the p-type region as the oxygen partial pressure increases. The transition points, which show the minimum conductivity, shifted to the higher oxygen partial pressure region as the measuring temperature increased, but it shifted to lower oxygen partial pressure region with an increase in the post annealing temperature. The results were also discussed with the possible defect models.

• The Korean Journal of Pharmacology
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• v.21 no.1
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• pp.34-48
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• 1985

In vitro effects of nitrofurantoin, an antimicrobial agent for acute and chronic urinary tract infection, on the lung microsomal lipid peroxidation and the generation of reactive oxygen radicals were investigated to elucidate the biochemical mechanisms of its in vivopulmonary toxicity. The interaction of nitrofurantoin with porcine lung microsome resulted in significant lipid peroxidation. In addition, nitrofurantoin stimulated the generation of reactive oxygen radicals, $O^{-}_{2}{\cdot},\;H_2O_2$ as well as a highly reactive secondary oxygen species, $OH{\cdot}$. The stimulation of lipid peroxidation was inhibited not only by superoxide dismutase and catalase, but also by hydroxyl radical scavengers, mannitol and thiourea. Neither singlet oxygen $({^1}O_{2})$ was detected during the incubation of microsome with nitrofurantoin, nor lipid peroxidation was inhibited by singlet oxygen scavengers. When incubated anaerobically under the nitrogen atmosphere, the ability of nitrofurantoin to stimulatle lipid peroxidation was abolished. It appears that NADPH-dependent metaboliam of nitrofurantoin in pulmonary microsome under aerobic condition is accompanied by the stimulation of lipid peroxidation through the mediation of reactive oxygen radicals, particularly hydroxyl radical. It is strongly suggested from these results that the stimulation of pulmonary microsomal lipid peroxidation by the reactive oxygen radical may be a in vivo mechanism of pulmonary toxicity caused by nitrofurantoin.

• Journal of the Korean Ceramic Society
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• v.27 no.7
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• pp.841-850
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• 1990

The electrical conductivity of SrTiO3 thick films, which has been prepared by screen printing and sintering on polycrystalline Al2O3 substrates, was determined as a function of oxygen partial pressure and temperature. The data showed that electrical conductivity was proportional to the -1/4th power of the oxygen partial pressure for the oxygen partial pressure range from 10-4-10-8 to 10-20 atm and proportional to Po2+1/4 for the oxygen partial pressure range from 10-6-10-4 to 1atm. And then n-p transition region of electrical conductivity moved to lower oxygen partial pressure region as the sintering temperature of thick film specimens increased under about 140$0^{\circ}C$. These data were consistent with the presence of small amounts of acceptor impurities in SrTiO3 thick film which have been diffused from Al2O3 substrate in the range of solid solubility limit.

• Journal of the Korean Chemical Society
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• v.33 no.2
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• pp.192-202
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• 1989

Tetradentate schiff bases cabalt (II) complexes; Co(SED) and Co(ο-BSDT) were synthesized and these complexes allowed to reaction with dry oxygen to form oxygen adduct cobalt(III) complexes such as $[Co(o-BSDT)(DMSO)]_2O_2,\;[Co(SED)(Py)]_2O_2\;and\;[Co(o-BSDT)(Py)]_2O_2$ in DMSO and pyridine solutions. It has been found that the oxygen adduct cobalt(III) complexes have hexacoordinated octahedral configuration with tetradentate schiff base cobalt(II), DMSO or pyridine and oxygen, and the mole ratio of oxygen to cobalt(II) complexes are 1:2. The redox processes, were investigated for Co(SEDT) and Co(ο-BSD) complexes in 0.1M TEAP-DMSO and 0.1M TEAP-pyridine by cyclic voltammetry with glassy carbon electrode. As a result the redox processes of Co(II)/Co(III) and Co(II)/Co(I) found to be reversible or quasi-reversible for non uptake oxygen complexes but oxygen adduct complexes found to be irreversible processes and reaction processes of oxygen for oxygen adduct complexes are quasi-reversible process, the potential range was $E_{pc}=-0.85{\sim}-1.19V\;and\;E_{pa}=-0.74{\sim}-0.89V$.

• Journal of the Korean Chemical Society
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• v.18 no.4
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• pp.259-266
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• 1974

Isotopic experiments using $H_2O^{18}$ on the oxidation of V(III) in acid perchlorate by molecular oxygen were performed in the range pH 1.0 to 3.0. At pH < 2, where a rate equation of the form TEX>$ -\frac{d[V(III)]}{dt}=k_1\frac{[O_2][V(III)]}{[H^+]}$ is adequate, the tracer study clearly indicated that all the product vanadyl ion's ($VO^{2+}$) oxygen originated from the molecular oxygen. At pH > ~2, where a different rate expression of the form $-\frac{d[V(III)]}{dt}=K_2\frac{[O_2][V(III)]^2}{[Ht]^2}$is required, the isotopic experiment showed that half the vanadyl oxygen originated from the molecular oxygen. Considering the results of the isotopic study, a mechanism for the V(Ⅲ)-O2 reaction at pH < ~2, may be suggested as follows: The tracer results at pH > ~2 imply that the rate determining step may be $$ V_2(OH)_2^{4+} + O_2 \rightarrow 2VO^{2+} + H_2O_2$$ followed by $$V_2(OH)_2^{4+} + H_2O_2 \rightarrow 2VO^{2+} + 2H_2O$$ after establishing the equilibria V^{3+} + H_2O \leftrightarrow VOH^{2+} + H^+, and 2VOH^{2+}\leftrightarrow V_2(OH)_2^{4+}$$

• Korean Journal of Materials Research
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• v.8 no.12
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• pp.1090-1098
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• 1998

$RuO_2$ thin films were deposited on Si and Ru/Si substrates by rf magnetron reactive sputtering and annealed in oxygen atmosphere(1atm) to investigate their thermal stability and diffusion barrier property. $RuO_2$ thin films were thermally stable up to 700\ulcorner for 10min. in oxygen atmosphere and showed excellent barrier property against the interdiffusion of silicon and oxygen. After annealing at $750^{\circ}C$ , however, volatilization to higher oxide occurred at the surface and inside of $RuO_2$ thin film and diffusion barrier property was also deteriorated. When annealed at $800^{\circ}C$, $RuO_2$thin film showed a different microstructure from that of $RuO_2$ thin film annealed at 75$0^{\circ}C$. It is likely that surface defect structure of $RuO_2$, $RuO_3$, and excess oxygen had an influence on the mode of volatilization with increasing annealing temperature.