• Journal of the Korean Ceramic Society
• /
• v.25 no.3
• /
• pp.243-250
• /
• 1988

The cross effect between an ion flux and an electronic current in a nonstoichiometric binary oxide, $A_{1-\delta}O_\mu$, has been analyzed in the light of irreversible thermodynamics. It has been shown that a net flux of the mobile cation vacancy is induced through the system in an electrical potential gradient applied across a pair of the reversible electrodes, which makes the Fick frame shift relative to the laboratory frame. As a consequence, the relative shift is a measure of the effective charge responsible for the cross effect. Two experiments are proposed to measure the shift.

• Applied Microscopy
• /
• v.42 no.4
• /
• pp.207-211
• /
• 2012

We examined the electrical properties and microstructure of NiO produced using a sol-gel method and Ni nitrate hexahydrate ($Ni[NO_3]_2{\cdot}6H_2O$) to investigate if this NiO thin film can be used as an insulator layer for resistance random access memory (ReRAM) devices. It was found that as-prepared NiO film was polycrystalline and presented as the nonstoichiometric compound $Ni_{1+x}O$ with Ni interstitials (oxygen vacancies). Resistances-witching behavior was observed in the range of 0~2 V, and the low-resistance state and high-resistance state were clearly distinguishable (${\sim}10^3$ orders). It was also demonstrated that NiO could be patterned directly by KrF eximer laser irradiation using a shadow mask. NiO thin film fabricated by the sol-gel method does not require any photoresist or vacuum processes, and therefore has potential for application as an insulating layer in low-cost ReRAM devices.

• Proceedings of the Korean Powder Metallurgy Institute Conference
• /
• 2006.09b
• /
• pp.1114-1115
• /
• 2006

The preparation of single-phase $CuLaO_2$ with delafossite-type structure by means of the solid-state reaction method was investigated using X-ray diffraction. The results showed that notwhistanding the fact that there was a trace of metallic copper, nearly single-phase $CuLaO_2$ was obtained by using $La(OH)_3$ as a lanthanum source and by firing the mixed powder with nonstoichiometric composition ratio of $La(OH)_3:Cu_2O=1:1.425$ in a vacuum at 1273 K for 10 h. The measurement of electrical conductivity and Seebeck coefficient showed that $CuLaO_2$ thus obtained was a p-type semiconductor and had a Seebeck coefficient of approximately $70{\mu}V/K$.

• Macromolecular Research
• /
• v.14 no.3
• /
• pp.267-271
• /
• 2006

Polyelectrolyte complex films were prepared with two compounds, chitosan and poly(ethylene glycol)-monosuccinate, using a casting in order to synthesize a polyelectrolyte complex film with various mole ratios of chitosan and poly(ethylene glycol)-monosuccinate. The solution properties of isolated PEC were investigated for the effects of FTIR, pH value, Brookfield viscosity and cell viability assay using MTT staining. The PEC films were evaluated for mechanical properties by typical stress-strain curve, far thermal properties by DSC and TGA and for surface morphology Properties by SEM. Furthermore, the surface resistance, moisture regain and water content of the films were characterized. The solution properties were affected by several factors including the chitosan content in the PEC, the mixing ratio of PEG and chitosan, and pH. Several PEC in acidic conditions exhibited film formation under appropriate conditions of mixing ratio and chitosan concentration in the mixing process. These PEC films were found to have sufficiently flexible and stable properties due to their hydrophilic structure, which was farmed by the oppositely charged interaction between PEG-MS and chitosan matrix. The results showed the potential applicability of chitosan and poly(ethylene glycol)-monosuccinate films as a biocompatible polymer.

• Journal of the Korean Ceramic Society
• /
• v.35 no.10
• /
• pp.1020-1029
• /
• 1998

The reaction-bonded TiC-Ni/Si/Co composites were prepared by the melt infiltration of Co, Si, and Ni me-tal into the TiC preforms. The miocrostructure reaction composition and mechanical properties were in-vestigated. In the case of the melt infiltrated with Co and Ni TiC grain shape was changed from angular to spherical shape with the average grain size of ∼5$\mu\textrm{m}$. In the case of the melt infiltrated with Co/Si or Ni/Si, Si was reacted with TiC particles and formed SiC particles. The bending strength of both specimens which have atomic ratio of 3 were 710 MPa and 515 MPa respectively. In the case of the melt infiltrated with Ni/Si/Co,. nonstoichiometric TiC was formed and its bending strength decreased to 420 MPa.

• Proceedings of the KIEE Conference
• /
• 1994.11a
• /
• pp.190-192
• /
• 1994

Microwave dielectric properties of $0.15(Ba_xSr_{0.05})O-0.15(Sm_{2(1-y)}Nd_{2y})O_3-0.7TiO_2$ ($x=0.9{\sim}1.0[mol.]$, y=6[m/0]) and $0.15(Ba_{0.95}Sr_{0.05})O-0.15(Sm_{2(1-y)}Nd_{2y})O_3-zTiO_2$(y=6[m/o], $z=0.66{\sim}0.7[mol.]$) ceramics were investigated with the contents of BaO and $TiO_2$. In the specimen with contents of BaO (0.975[mol.]), dielectric constant, quality factor and temperature coefficient of resonant frequency have good values of 76.52, 3001(at 3[GHz]), +0.71[ppm/$^{\circ}C$], respectively. In the specimen with contents of $TiO_2$(0.69[mol.]), dielectric constant, quality factor and temperature coefficient of resonant frequency showed the maximum values of 80.89, 3057(at 3[GHz]), +26.12[ppm/$^{\circ}C$], respectively.

• Electrical & Electronic Materials
• /
• v.9 no.7
• /
• pp.719-726
• /
• 1996

DLTS measurements were performed to study the annealing induced changes of the trap centers in MOV and to shed more light on the stability mechanism of the MOV. Two electron traps, Ec-0.26[eV] and Ec-(O.2-0.3)[eV], were observed in the unannealed samples in large quantities(7-9 X 1014[CM 3]), whereas the three electron traps Ec-0.17 [eV], Ec-0.26[eV] and Ec-(O.2-0.3)[eV] were observed far less in the annealed samples. The minima in the Ec-0.26[eV] trap density, coupled with the presented results that unannealed devices are unstable whereas 600.deg. C annealed devices are most stable, suggests that the instability of the MOV under long term electrical stressing is related to the Ec-0.26[eV] trap. This results support that the ion migration model for the device instability where the Ec-0.26[eV] defects may be the interstitial zinc or the migrating ions. The interstitial zinc originated as a result of the nonstoichiometric nature of ZnO might cause the degradation of the I-V characteristics of the MOV with long term electrical stressing.

• Journal of the Korean Vacuum Society
• /
• v.4 no.S2
• /
• pp.95-99
• /
• 1995

keV ion beam irradiatin for surface modification and thin film growth have been discussed. keV ion beam irradiation in reactive gas environment has been developed for improving wettability of polymer, and for enhancing adhesion to metal film, and adventages of the method have been reviewed. An epitaxial Cu film on Si(100) substrate has been grown by ionized cluster beam and changes of crystallinity and surface roughness have been discussed. Stoichiometric $SnO_2$ films on Si(100) and glass have been grown by a hybrid ion beam Deposition(2 metal ion sources+1 gas ion source), and nonstoichiometric $SnO_2$ films are controlled by various deposition conditions in the HIB. Surface modification for polymer by kev ion irradiation have been developed. Wetting angle of water to PC has been changed from 68 degree to 49 degree with $Ar^+$ irradiation and to 8 degree with $Ar^+$ irradiation and the oxygen environment. Change of surface phenomena in a keV ion beam and characteristics of the grown films are suggested.

• Bulletin of the Korean Chemical Society
• /
• v.15 no.1
• /
• pp.33-36
• /
• 1994

The x values of nonstoichiometric chemical formula, $Tb_4O_{7-{\delta}}\;or\;TbO_{1.5+x}$, have been determined in temperature range from 600$^{\circ}$C to 1000$^{\circ}$C under oxygen partial pressure of 2 ${\times}$ 10$^{-1}$ to 1 ${\times}$ 10$^{-5}$ atm by using quartz microbalance. The x values varied from 0.0478 to 0.1964 in the above conditions. The enthalpy of formation for x' in TbO$_{1.5+(0.25-xo-x')}$, ${\delta}H_f$, was 4.93-3.40 kcal mol$^{-1}$ and the oxygen partial pressure dependence was -1/8.80∼-1/11.8 under these conditions. The electrical conductivity of the $TbO_{1.5+x}$ was measured under the same conditions and the values varied from about 10$^{-3}$ to 10$^{-6}\;{\Omega}^{-1}cm^{-1}$ within semiconductor range. The activation energies for the conduction increase with oxygen partial pressure from 0.83 to 0.89 eV under the above conditions. The l/n values obtained from the oxygen pressure dependence of the conductivity are 1/4.4-1/5.2. The conduction mechanism, defect structure, and other physical properties of the oxides are dicussed with the x values, the electrical conductivity values, and the thermodynamic data.

• Bulletin of the Korean Chemical Society
• /
• v.15 no.7
• /
• pp.541-545
• /
• 1994

A series of samples of the ${Ca_xEu_{1-x}FeO_{3-y}$ (x=0.00, 0.25, 0.50, 0.75, and 1.00) system has been prepared at $1,250^{\circ}C$ under an atmospheric air pressure. X-ray diffraction analysis of the solid solution assigns the structure of the compositions of x=0.00, 0.25, 0.50, and 0.75 to the orthoferrite-type orthorhombic system, and that of x=1.00 to the brownmillerite-type orthorhombic one. The mole ratios of $Fe^{4+}$ ion in the solid solutions or ${\tau}$ values were determined by the Mohr's salt analysis and nonstoichiometric chemical formulas of the system were formulated from x, ${\tau}$, and y values. From the result of the Mossbauer spectroscopy, the coordination and magnetic property of the iron ion are discussed. The electrical conductivities are measured as a function of temperature. The activation energy is minimum at the composition of x=0.25. The conduction mechanism can be explained by the hopping of electrons between the mixed valences of $Fe^{3+}\;and\;Fe^{4+}$ ions.