• Korean Journal of Materials Research
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• v.33 no.5
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• pp.195-204
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• 2023

Micro-electronic gas sensor devices were developed for the detection of carbon monoxide (CO), nitrogen oxides (NO_x), ammonia (NH₃), and formaldehyde (HCHO), as well as binary mixed-gas systems. Four gas sensing materials for different target gases, Pd-SnO₂ for CO, In₂O₃ for NO_x, Ru-WO₃ for NH₃, and SnO₂-ZnO for HCHO, were synthesized using a sol-gel method, and sensor devices were then fabricated using a micro sensor platform. The gas sensing behavior and sensor response to the gas mixture were examined for six mixed gas systems using the experimental data in MEMS gas sensor arrays in sole gases and their mixtures. The gas sensing behavior with the mixed gas system suggests that specific adsorption and selective activation of the adsorption sites might occur in gas mixtures, and allow selectivity for the adsorption of a particular gas. The careful pattern recognition of sensing data obtained by the sensor array made it possible to distinguish a gas species from a gas mixture and to measure its concentration.

• Current Photovoltaic Research
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• v.11 no.4
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• pp.103-107
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• 2023

A Nickel oxide (NiO_x) thin films were prepared via sol-gel process on a transparent conductive oxide glass substrate. The NiO_x thin films were spin-coated in ambient air and subsequently annealed for 30 minutes at temperatures ranging from 150℃ to 450℃. The structural and optical characteristics of the NiO_x thin films annealed at various temperatures were measured using X-ray diffraction, field emission scanning electron microscopy, and ultraviolet-visible spectroscopy. After optimizing the NiO_x coating conditions, perovskite solar cells were fabricated with p-i-n inverted structure, and its photovoltaic performance was evaluated. NiO_x thin films annealed at 350℃ exhibited the most favorable characteristics as a hole transport layer, resulting in the highest power conversion efficiency of 17.88 % when fabricating inverted perovskite solar cells using this film.

• Journal of Ceramic Processing Research
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• v.22 no.2
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• pp.214-220
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• 2021

Heterolayered potassium tantalate niobate(KTN(70/30)/KTN(30/70)) thin films on Pt/Ti/SiO2/Si substrates prepared by the sol-gel process and spin coating method. When sintered at 700 ℃ or higher, the X-ray diffraction intensities of the perovskite phase were greatly increased, and it was observed as the main phase of the KTN heterolayered thin film. As the sintering temperature increased from 650 ℃ to 800 ℃, the average grain size increased from 146nm to 380 nm, and the average thickness of the KTN films coated six times was about 394-441 nm. Dielectric constant and dielectric loss of the KTN film sintered at 750 ℃ and room temperature showed good properties of about 2850 and 0.573, respectively, and all films exhibited the typical dielectric relaxation characteristics. The phase transition temperature of KTN thin film was around 12-13 ℃. Remanent polarization and the coercive field of KTN film sintered at 750 ℃ showed excellent properties of 23.98 μC/cm2 and 35.41 kV/cm, respectively. Adiabatic temperature changes (ΔT) and electrocaloric strength of the KTN films sintered at 750 ℃ at 60 ℃ were 2.67℃ and 0.012 KcmkV-1, respectively.

• Journal of the Korean Ceramic Society
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• v.42 no.7 s.278
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• pp.475-482
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• 2005

Zn$_{l-x}$Co$_{x}$O (x = 0.05 - 0.20) films were grown on Coming 7059 glass by sol-gel process. A homogeneous and stable Zn$_{l-x}$Co$_{x}$O sol was prepared by dissolving zinc acetate dihydrate (Zn(CH$_{3}$COO)$_{2}$$\cdot$2H$_{2}$O), cobalt acetate tetrahydrate ((CH$_{3}$)$_{2}$$\cdot$CHOH) and aluminium chloride hexahydrate (AlCl$_{3}$ $\cdot$ 6H$_{2}$O) as solute in solution of isopropanol ((CH$_{3}$)$_{2}$$\cdot$CHOH) and monoethanolamine (MEA:H$_{2}$NCH$_{2}$CH$_{2}$OH). The films grown by spin coating method were postheated in air at 650°C for 1 h and annealed in the condition of vacuum (5 $\times$ 10$^{-6}$ Torr) at 300$^{\circ}C$ for 30 min and investigated the nature of c-axis preferred orientation and physical properties with different Co concentrations. Znl_xCOxO thin films with different Co concentrations were well oriented along the c-axis, but especially a highly c-axis oriented Zn$_{l-x}$Co$_{x}$O thin film was grown at 10 at$\%$ Co concentration. The transmittance spectra showed that Zn$_{l-x}$Co$_{x}$O thin films occur typical d-d transitions and sp-d exchange interaction became activated with increasing Co concentration. The electrical resistivity of the films at 10 at$\%$ Co had the lowest value due to the highest c-axis orientation. X-ray photoelectron spectroscopy and alternating gradient magnetometer analyses indicated that no Co metal cluster was formed, and the ferromagnetic properties appeared, respectively. The characteristics of the electrical resistivity and room temperature ferromagnetism of Zn$_{l-x}$Co$_{x}$O thin films suggested the possibility for the application to dilute magnetic semiconductors.

• Journal of the Korean Ceramic Society
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• v.41 no.2
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• pp.170-175
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• 2004

The ferroelectric (Y $b_{x}$ $Y_{1-x}$)Mn $O_3$ thin films were fabricated by sol-gel method using Y-acetate, Yb-acetate, and Mn-acetate as raw materials. The stable (Y $b_{x}$ $Y_{1-x}$)Mn $O_3$ precursor solution (sol) was prepared through the reflux process with acetylaceton as a catalyst and coated on Si(100) substrate by spin coating. The heat treatment temperature and, Rw ($H_2O$/alkoxide moi ratio) dependence on crystallinity of thin films were studied. The lowest temperature for obtaining YbMn $O_3$phase and the optimum heat-treatment conditions were proved as at 7$50^{\circ}C$ and 80$0^{\circ}C$, respectively. The hexagonal YbMn $O_3$with c-axis preferred orientation could be obtained at Rw=1 condition. The remanent polarization for the thin films of x=0 or 1 was about 200 nC/㎤ while, for the specimens ot 0< x< 1, were 50∼100 nC/$\textrm{cm}^2$.

• Journal of the Korean Ceramic Society
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• v.39 no.10
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• pp.1001-1006
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• 2002

Bond strength of $SrZrO_3$ resistive oxide barrier on Ag sheathed Bi(2223) tapes prepared by the sol-gel and dip-coating method was evaluated with an aid of Taguchi method and $L_18(2^1{\times}3^7)$ orthogonal arrays to determine the optimal process combination of levels of factors that best satisfy the bigger is better quality characteristic. The observed optimal condition is as follows: Sr/Zr mol ratio(0.3/0.7), amount of organic vehicle(5 wt%), drying temperature and time(160${\circ}C$, 10 min), heat treatment temperature and time(500${\circ}C$, 20 min), respectively. ANOVA analysis suggested that the influence of the factors within ${\alpha}$=0.1 was significant with a 90% confidence level.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.10 no.3
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• pp.211-218
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• 2000

$PbZrO_3$precursor was prepared for the spin coating on the Pt/Ti/$SiO_2$/Si substrate. Two different heat treatment methods were used and the differencies were studied. One of the method is that the films were inserted into the furnace for 30 minutes and the other is that the films were annealed by rapid thermal annealing (RTA) for 1 minute at the same temperatures. We also examined the tendency of crystallization by annealing at the fixed temperature, $700^{\circ}C$ as a function of time, namely during 1, 10, 20, and 30 minitues, respectively. The optimum conditions for the crystallization of these films were at $550^{\circ}C$ during 30 min. and at $700^{\circ}C$ during 10 min. in muffle furnace and at $650^{\circ}C$ during 1 min in RTA furnace. The best condition for making good quality grains needs 30 min. at $700^{\circ}C$.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.367-367
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• 2014

Transparent conductive oxides (TCOs) 박막은 가시광선영역에서의 높은 투과율과 낮은 저항 특성을 동시에 갖고 있어 최근 smart windows, solar cells, liquid crystal displays (LCD), organic light emitting devices (OLED)등과 같은 최첨단 기기에 필수적인 구성요소로 활발히 사용되고 있다. 따라서, 현재까지 FTO ($SnO_2:F$), ITO ($In_2O_3:Sn$), ATO ($SnO_2:Sb$)등과 같은 다양한 TCO들이 많은 연구자들에 의해 연구되고 있다. 그 중 ITO는 우수한 전기적(${\sim}10^{-4}{\Omega}cm$) 및 광학적(~85%) 특성 때문에 현재 상업적으로 활발히 응용되고 있는 대표적인 물질이다. 하지만 ITO의 주된 구성요소인 indium은 제한적인 매장량과 과도한 소비량 때문에 원가가 비싸다는 문제점이 있다. 반면에, ATO는 우수한 전기적(${\sim}10^{-3}{\Omega}cm$) 및 광학적(~80%) 특성뿐만 아니라 구성물질들의 매장량이 풍부하여 ATO의 원가가 저렴하다는 장점을 가지고 있어 현재 ITO을 대체 할 수 물질로 관심 받고 있다 [1]. 지금까지 우수한 특성을 갖는 ATO박막을 합성하는 방법으로 sol-gel spin coating, sputtering, spray pyrolysis, chemical vapor deposition (CVD)등이 알려져 있다. 이 중에서도, sol-gel spin coating과 spray pyrolysis은 solution기반의 합성법으로 분류되며 합성과정이 간단하고 비용이 저렴하다는 장점이 있고 현재까지 많은 연구가 보고되었다. 그러나, 진공기반이 아닌 우수한 특성을 갖는 solution기반의 ATO박막을 합성하기 위해서는 새로운 합성법의 개발이 학문적으로나 산업적으로도 매우 중요한 이슈이다. 따라서, 본 연구에서는 electrospray을 활용하여 solution기반의 ATO박막을 처음으로 합성하였다. 게다가 ATO박막에 열처리온도에 따른 구조, 화학, 전기, 광학적 특성을 확인하기 위하여 X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Scanning Electron Microscopy (SEM), transmission electron microscopy (TEM), Hall Effect Measurement System, UV spectrophotometer를 사용하였다. 이러한 실험 결과들을 바탕으로 electrospray을 통해 합성된 solution기반의 ATO박막에 자세한 특성을 본 학회에서 다루도록 하겠다.

• Bulletin of the Korean Chemical Society
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• v.33 no.11
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• pp.3767-3771
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• 2012

In this study, we investigate the potential use of $TiO_2@SiO_2$ and $ZnO@SiO_2$ core/shell nanoparticles (NPs) as effective UV shielding agent. In the typical synthesis, $SiO_2$ was coated over different types of $TiO_2$ (anatase and rutile) and ZnO by sol-gel method. The synthesized $TiO_2@SiO_2$ and $ZnO@SiO_2$ NPs were characterized by UV-Vis, XRD, SEM and TEM. The UV-vis absorbance and transmittance spectra of core@shell NPs showed an efficient blocking effect in the UV region and more than 90% transmittance in the visible region. XRD and SAED studies confirmed the formation of amorphous $SiO_2$ coated over the $TiO_2$ and ZnO NPs. The FESEM and TEM images shows that coating of $SiO_2$ over the surface of anatase, rutile $TiO_2$ and ZnO NPs resulted in the increase in particle size by ~30 nm. In order to study the UV light shielding capability of the samples, photocatalytic degradation of methylene blue dye on $TiO_2@SiO_2$ and $ZnO@SiO_2$ NPs was performed. Photocatalytic activity for both types of $TiO_2$ NPs was partially suppressed. In comparison, the photocatalytic activity of ZnO almost vanished after the $SiO_2$ coating.

• Journal of the Korean Magnetics Society
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• v.15 no.1
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• pp.21-24
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• 2005

This work is to present each properties and the interfacial characterization between PZT layer and LSMO layer of PZT/LSMO/Pt. LSMO thin film grown by KrF(248 nm) excimer lasers are used in pulsed in pulsed laser deposition(PLD). PZT coposites thin films were deposited by spin coating using a commercial resist spinner. LSMO thin film by deposition oxygen pressure 125 mtorr have rhombohedral structure on Pt(111) substrate. The PZT/LSM/Pt pre-orientate to [111] direction. The final thin films were shown that magnetic and electric property was typical value, respective. We report that the lattice between the PZT/LSMO thin film and the substrate plays a very important role and may control to another effects.