• Journal of the Microelectronics and Packaging Society
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• v.27 no.4
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• pp.77-81
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• 2020

Resistive RAM (ReRAM) is a strong candidate for the next-generation nonvolatile memories which use the resistive switching characteristic of transition metal oxides. The resistive switching behaviors originate from the redistribution of oxygen vacancies inside of the oxide film by applied programming voltage. Therefore, controlling the oxygen vacancy inside transition metal oxide film is most important to obtain and control the resistive switching characteristic. In this study, we introduced an applying electric field into photochemical metal-organic deposition (PMOD) process to control the oxidation state of metal oxide thin film during the photochemical reaction by UV exposure. As a result, the surface oxidation state of FeOx film could be successfully controlled by the electric field-assisted PMOD (EFAPMOD), and the controlled oxidation states were confirmed by x-ray photoelectron spectroscopy (XPS) I-V characteristic. And the resistive switching characteristics with the oxidation-state of the surface region could be controlled effectively by adjusting an electric field during EFAPMOD process.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.6
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• pp.518-523
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• 2002

The influences of ion beam energy and reactive oxygen partial pressure on the physical and crystallographic characteristics of transition metal oxide compound(CrOx) film were studied in this paper. Chromium oxide films were deposited onto a cover-glass using ion Beam Sputter Deposition(IBSD) technique according to the various processing parameters. Crystallinity and grain size of as-deposited films were analyzed using XRD analysis. Thickness and Resistivity of the films were measured by $\alpha$-step and 4-point probe measurement. According to the XRD, XPS and resistivity results, the deposited films were the cermet type films which had crystal structure including amorphous oxide(a-oxide) phase and metal Cr phase simultaneously. The increment of the ion beam energy during the deposition process led to decreasing of metal Cr grain size and the rapid change of resistivity above the critical $O_2$ partial pressure.

• Applied Chemistry for Engineering
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• v.26 no.2
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• pp.128-131
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• 2015

Hydration of nitriles in the environmentally benign neutral conditions is the most economical and attractive way to produce amides. Substantial research works have been carried out to apply the solid metal oxides and transition metal supported catalytic systems to promote the hydration of nitriles. The most significant feature of these catalysts is the applicability to a wide range of substrates including aromatic, alicyclic, hetero-atomic, and aliphatic nitriles. These catalysts are also characterized by the easy isolation from the reaction mixture and the reusability while maintaining the high catalytic activity. This review accounts over the detailed survey of the metal oxide and solid supported metal catalysts for preparing amides from the hydration of nitriles.

• Journal of IKEEE
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• v.23 no.4
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• pp.1128-1133
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• 2019

This paper proposed colored front panel glass for Building Integrated Photovoltaic (BIPV) systems using multi-layered thin films composed of transition metal oxide (TMO) layers. Molybdenum oxide (MoO₃) and tungsten oxide (WO₃) provided complementary and suitable materials in making effective interference of reflected light from interfaces with significant difference in refractive indices. A simple, fast, and cheap fabrication method was achieved by depositing the multi-layer films in a single thermal evaporator. Magenta colored glass with optical transmittance of more than 90% was achieved with MoO₃ (60nm)/WO₃(100nm) multi-layered film. This technology could play in a critical role in commercial BIPV system applications.

• Journal of the Korean Vacuum Society
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• v.12 no.S1
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• pp.100-103
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• 2003

The magnetoresistance (MR) of $La_{1-\chi}S_{\chi}CoO_{3-\delta}$ films prepared by pulsed-laser deposition were investigated in order to clarify the magnetotransport properties around the metal-insulator transition. For the films in the metallic state ($\chi$ > 0.25), the MR(T) manifests a small peak at the Curie temperature due to the spin-disorder scattering. The transition of the film into the insulating state ($\chi\;\leq$ 0.25) is accompanied by an essential growth of the MR and results in a significant increase in the MR(T) with decreasing temperature, due to a phase separation into the ferromagnetic-metal clusters and the insulating matrix.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.424.1-424.1
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• 2014

Vanadium dioxide (VO2) is a strongly correlated oxide exhibiting a first-order metal-insulator transition (MIT) that is accompanied by a structural phase transition from a low temperature monoclinic phase to a high-temperature rutile phase. VO2 has attracted significant attention because of a variety of possible applications based on its ultrafast MIT. Interestingly, the transition nature of VO2 is significantly affected by stress due to doping and/or interaction with a substrate and/or surface tension as well as defects. Accordingly, there have been considerable efforts to understand the influences of such factors on the phase transition and the fundamental mechanisms behind the MIT behavior. Here, we present the influences of oxygen deficiency, hydrogen doping, and substrate-induced stress on MIT phenomena in single-crystalline VO2 nanobeams. Specifically, the work function and the electrical resistance of the VO2 nanobeams change with the compositional variation due to the oxygen-deficiency-related defects. In addition, the VO2 nanobeams during exposure to hydrogen gas exhibit the reduction of transition temperature and the complex phase inhomogenieties arising from both substrate-induced stress and the formation of the hydrogen doping-induced metallic rutile phase.

• Transactions on Electrical and Electronic Materials
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• v.11 no.1
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• pp.1-10
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• 2010

This is an overview paper reporting our most recent work on processing and microstructure of nano-structured oxides and their photoluminescence and photo-catalysis properties. Zinc oxide and related transition metal oxides such as vanadium pentoxide and titanium dioxide were produced by a combination of magnetron sputtering, hydrothermal growth and atmosphere controlled heat treatment. Special morphology and microstructure were created including nanorods arrays, core-brushes, nano-lollipops and multilayers with very large surface area. These structures showed special properties such as much enhanced photoluminescence and chemical reactivity. The photo-catalytic properties have also been promoted significantly. It is believed that two factors contributed to the high reactivity: the large surface area and the interaction between different oxides. The transition metal oxides with different band gaps have much enhanced photoluminescence under laser stimulation. Use of these complex oxide structures as electrodes can also improve the energy conversion efficiency of solar cells. The mixed oxide complex may provide a promising way to high-efficiency photo emitting materials and photo-catalysts.

• Journal of Powder Materials
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• v.8 no.3
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• pp.186-191
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• 2001

Several fabrication processes, corresponding nanostructural features and multifunctionality as well has been investigated for oxide ceramic based nanocomposites with metal nanodispersion (i.e., ceramic/metal nanocomposites). Transition metal (Ni, Co, etc) dispersed alumina and zirconia based nanocomposites have been synthesized by reducing and hot-press sintering of ceramic and metal oxide mixtures prepared by several method. Improved fracture strength (1.1 and 1.9 GPa for $Al_2O_3/Ni$ and $ZrO_2/Ni$ nanocomposites, respectively) of these composites have been achieved according to their nanostructures. In addition, ferromagnetic characteristic has been kept. The variation of magnetization with an applied stress has found to be more sensitive as smaller as the magnetic metal dispersion is. This result thus suggests the possibility of fracture and/or stress sensing of the composites by simple magnetic measurement.

• Journal of the Korean Magnetics Society
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• v.21 no.1
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• pp.1-4
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• 2011

We have studied magnetic structure and magnetic anisotropy energy of cubic transition metal mono-oxide cluster FeO and MnO using OpenMX method based on density functional method. The calculation results show that the antiferromagnetic spin arrangement has the lowest energy for FeO and MnO due to the superexchange interactions. The magnetic anisotropy is only found for antiferromagnetically ordered FeO cluster, since occupied electron of 3d down-spin level induces the spin-orbit couplings with <111> directed angular momentum.

• Journal of the Korean Electrochemical Society
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• v.12 no.1
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• pp.1-10
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• 2009

This article reviewed transport behaviours of electroactive species in ionic compounds, focusing on chemical diffusion of Li through the transition metal oxide in a current flowing condition. For this purpose, a distinction has been first briefly made between migration and diffusion with respect to current, driving force and charge of electroactive species considered. Then, the equations for chemical diffusion are derived theoretically in open-circuit and current flowing conditions. Finally, the experimental methods such as ac impedance spectroscopy and current (potential) transient techniques are described in details for characterising chemical diffusion. In addition, the role of the thermodynamic enhancement factor in chemical diffusion is discussed.