• Korean Journal of Materials Research
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• v.30 no.6
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• pp.285-291
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• 2020

Recent advances in technology using ultra-thin noble metal film in oxide/metal/oxide structures have attracted attention because this material is a promising alternative to meet the needs of transparent conduction electrodes (TCE). AZO/Ag/AZO multilayer films are prepared by magnetron sputtering for Cu₂ZnSn(S,Se)₄ (CZTSSe) of kesterite solar cells. It is shown that the electrical and optical properties of the AZO/Ag/AZO multilayer films can be improved by the very low resistivity and surface plasmon effects due to the deposition of different thicknesses of Ag layer between oxide layers fixed at AZO 30 nm. The AZO/Ag/AZO multilayer films of Ag 15 nm show high mobility of 26.4 ㎠/Vs and low resistivity and sheet resistance of 3.58^⁎10^-5 Ωcm and 5.0 Ω/sq. Also, the AZO/Ag (15 nm)/AZO multilayer film shows relatively high transmittance of more than 65 % in the visible region. Through this, we fabricated CZTSSe thin film solar cells with 7.51 % efficiency by improving the short-circuit current density and fill factor to 27.7 mV/㎠ and 62 %, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.1080-1083
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• 2001

Ultrafine NiO/YSZ composite powders were prepared by using a glycine nitrate process for anode material of solid oxide fuel cells. The specific surface areas of synthesized NiO/YSZ composite powders were examined with controlling pH of a precursor solution and the content of glycine. The characteristics of synthesized composite powders were examined with X-ray diffractometer, a BET method with N$_2$absorption, scanning and transmission electron microscopy. The strongly acid precursor solution increased the specific surface area of the synthesized composite powders. This is suggested to be caused by the increased binding of metal ions and glycine under a strong acid solution of pH=0.5 that lets glycine consist of mainly the amine group of NH$_3$$\^$+/. After sintering and reducing treatment of NiO/YSZ composite powders synthesized by GNP, the Ni/YSZ pellet showed ideal micro-structure very fine Ni parties of 3-5${\mu}$m were distributed uniformly and fine pores around Ni metal particles were formed, thes, leading to an increase of the triple phase boundary among gas Ni and YSZ.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.12
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• pp.808-812
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• 2015

Highly optical transparent photoelectric devices were realized by using a transparent metal-oxide semiconductor heterojunction of p-type NiO and n-type ZnO. A functional template of ITO nanowires (NWs) was applied to this transparent heterojunction device to enlarge the light-reactive surface. The ITO NWs/n-ZnO/p-NiO heterojunction device provided a significant high rectification ratio of 275 with a considerably low reverse saturation current of 0.2 nA. The optical transparency was about 80% for visible wavelengths, however showed an excellent blocking UV light. The nanostructured transparent heterojunction devices were applied for UV photodetectors to show ultra fast photoresponses with a rise time of 8.3 mS and a fall time of 20 ms, respectively. We suggest this transparent and super-performing UV responser can practically applied in transparent electronics and smart window applications.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.19 no.4
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• pp.202-207
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• 2009

Nanocomposite formation of metal-metal oxide systems by mechanical alloying (MA) has been investigated at room temperature. The systems we chose are the $Fe_3O_4$-M (M = AI, Ti), where pure metals are used as reducing agent. It is found that $Fe/Al_2O_3$ and $Fe/TiO_2$ nanocomposite powders in which $Al_2O_3$ and $TiO_2$ are dispersed in ${\alpha}$-Fe matrix with nano-sized grains are obtained by MA of $Fe_3O_4$ with Al and Ti for 25 and 75 hours, respectively. It is suggested that the shorter MA time for the nanocomposite formation in $Fe/Al_2O_3$ is due to a large negative heat associated with the chemical reduction of magnetite by aluminum. X-ray diffraction results show that the average grain size of ${\alpha}$-Fe in $Fe/TiO_2$ nanocomposite powders is in the range of 30 nm. The change in magnetic properties also reflects the details of the solid-state reduction of magnetite by pure metals during MA.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.37 no.2
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• pp.208-214
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• 2024

This reports the electrical properties of single-crystal β-gallium oxide (β-Ga₂O₃) vertical Schottky barrier diodes (SBDs) with a different guard ring structure. The vertical Schottky barrier diodes (V-SBDs) were fabricated with two types guard ring structures, one is with metal deposited on the Al₂O₃ passivation layer (film guard ring: FGR) and the other is with vias formed in the Al₂O₃ passivation layer to allow the metal to contact the Ga₂O₃ surface (metal guard ring: MGR). The forward current values of FGR and MGR V-SBD are 955 mA and 666 mA at 9 V, respectively, and the specific on-resistance (R_on,sp) is 5.9 mΩ·cm² and 29 mΩ·cm². The series resistance (R_s) in the nonlinear section extracted using Cheung's formula was 6 Ω, 4.8 Ω for FGR V-SBD, 10.7 Ω, 6.7 Ω for MGR V-SBD, respectively, and the breakdown voltage was 528 V for FGR V-SBD and 358 V for MGR V-SBD. Degradation of electrical characteristics of the MGR V-SBD can be attributed to the increased reverse leakage current caused by the guard ring structure, and it is expected that the electrical performance can be improved by preventing premature leakage current when an appropriate reverse voltage is applied to the guard ring area. On the other hand, FGR V-SBD shows overall better electrical properties than MGR V-SBD because Al₂O₃ was widely deposited on the Ga₂O₃ surface, which prevent leakage current on the Ga₂O₃ surface.

• Korean Journal of Materials Research
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• v.9 no.4
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• pp.414-418
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• 1999

Typical metal oxide thin films having optical and electrical properties are widely used as inorganic functional materials. Liquid phase deposition(LPD) method, a new low temperature process, has been developed for the several advantages of no vacuum system, low cost, high throughput, and low processing temperature(<$50^{\circ}C$). Silica powder was added to 40wt% hydrofluoro-silicic acid($H_2$SiF\ulcorner) to obtain an immersing solution of silica-saturated hydrofluorosilicic acid solution. Boric acid solution was continuously added in the range from 0 to 0.05M to prepare supersaturated hydrofluorosilicic acid solution. LPD $SiL_2$film was formed with the variation of added amount of $H_2$O. The SiO$_2$thin film could be prepared from hydrofluorosilicic acid by LPD method. The thickness of LPD $_SiO2$film was influenced by the boric acid concentration and added amount of $H_2$O. Silicon in thin film existed as SiF\ulcorner by Raman spectrum.

• Journal of Sensor Science and Technology
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• v.17 no.4
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• pp.281-288
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• 2008

Polyacrylonitrile(PAN)/metal oxide(MO) nanocomposite mats with a thickness of 0.12 mm were electrospun by adding 0 to 10 wt% of MO nanoparticles ($Fe_2O_3$, ZnO, $SnO_2$, $Sb_2O_3-SnO_2$) into PAN. Pt electrode was patterned on $Al_2O_3$ substrate by DC sputtering and then the PAN(/MO) mats on the Pt patterned $Al_2O_3$ were electrically wired to investigate the $CO_2$ gas sensing properties. As the MO content rose, the fiber diameter decreased due to the presence of lumps caused by the presence of MOs in the fiber. The PAN/2% ZnO mat revealed a faster response time of 93 s and a relatively short recovery of 54 s with a ${\Delta}R$ of 0.031 M${\Omega}$ at a $CO_2$ concentration of 200 ppm. The difference in sensitivity was not observed significantly for the PAN/MO fiber mats in the $CO_2$ concentration range of 100 to 500 ppm. It can be concluded that an appropriate amount of MO nanoparticles in the PAN backbone leads to improvement of the $CO_2$ gas sensing properties.

• Applied Chemistry for Engineering
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• v.17 no.4
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• pp.420-425
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• 2006

Nano sized mixed metal hexagonal ferrite powders with improved magnetic properties have been prepared by sol-gel method using propylene oxide as a gelation agent. To obtain the desired ferrite, two different metal ions were used. One of the ions has only +2 formal charge. The key step in the processes is that hydrated $Ba^{2+}$ or $Sr^{2+}$ ions are hydrolyzed and condensed at the surface of the previously formed $Fe_{2}O_{3}$ gel. In this processes, all the reaction can be finished within a few minutes. The magnetic properties of the produced powder were improved by heat treatment. The highest values of the magnetic properties were achieved at temperature $150^{\circ}C$ lower than those of the previously published values. The highest observed values of coercivity and the saturation magnetization of Sr-ferrite and Ba-ferrite powder were 6198 Oe, 5155 Oe and 74.4 emu/g, 68.1 emu/g, respectively. The ferrite powder annealed at $700^{\circ}C$ showed spherical particle shapes. The resulting spheres which were formed by the aggregation of nanoparticles with size 3~5 nm have diameter around 50 nm. The powder treated at $800^{\circ}C$ showed hexagonal-shaped grains with crystallite size above 500 nm.

• Journal of the Korean Institute of Telematics and Electronics
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• v.21 no.4
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• pp.52-57
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• 1984

The electrical properties and their instability of InP tunnel MIS diodes fabricated by inserting the chemically grown oxide between metal and n-lnP (100) surface have been in-vestigated. The structure of the gown oxide was the mixture of In2O3 and P2O5, as was other low-temperature grown oxide, and its thickness was estimated to be the order of 200 $A^{\circ}$. The forward and reverse currents increased even with slight heat treatment of diodes in vacuum, and they were reduced when the diodes were exposed to humid ambient. It was discussed that the observed instability in I-V characteristics is due to a change of the physicochemical properties of the oxide film and of the interface states between oxide and InP according to the absorption of H2O.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.336-337
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• 2005

ZnO varistor ceramics were fabricated as a function of the amount of $Y_2O_3$ addition and sintered at $1250^{\circ}C$ for 2 hour. The average grain size was decreased from 14.2 ${\mu}m$ to 8.3 ${\mu}m$ with the amount of $Y_2O_3$ addition, and varistor voltage was increased from 433 V to 563 V with $Y_2O_3$ addition. Nonlinear coefficient a of all specimens were increased with the amount of $Y_2O_3$ more than 67, in case of $Y_2O_3$ 0.01wt% addition showed the excellent results of 87. And leakage current was less than $1{\mu}A$ at 82% of varistor voltage. The clamping voltage ratio of the specimens added 0.01wt% $Y_2O_3$ was 1.41 at 25A [8/20${\mu}s$]. At the specimen 0.01wt% $Y_2O_3$ addition. endurance of surge current and deviation of varistor voltage were 5700A/$cm^2$ and $\Delta$-2.86%, respectively.