• Korean Chemical Engineering Research
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• v.59 no.2
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• pp.281-295
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• 2021

In this study, the direct amination of ethanol was performed over impregnated Ni on SiO2-Al2O3 mixed oxide catalysts prepared by varying Si/(Si + Al) molar ratio to 30 mol%. To characterize the physico-chemical properties of the catalysts used, X-ray diffraction (XRD), N2-physisorption, temperature-programmed desorption of iso-propyl alcohol (IPA-TPD), temperature-programmed desorption of ethanol (EtOH-TPD), temperature-programmed reduction with H2 (H2-TPR), H2-chemisorption and transmission electron microscopy (TEM) were used. The acidic property was continuously increased until Si/(Si + Al) = 30 mol% in SiO2-Al2O3 mixed oxides used. The dispersion of Ni metal and surface area, acid characteristics of the supported Ni catalyst have a complex effect on the catalytic reaction activity. The low reduction temperature of nickel oxide and acidic properties were beneficial to the formation of acetonitrile. In terms of conversion of ethanol, Ni/SiO2-Al2O3 catalyst with a molar ratio of 10 mol% Si/(Si+Al) showed the highest activity and a volcanic curve based on it. The tendency of results were consistent in the metal dispersion and catalytic activity.

• Transactions on Electrical and Electronic Materials
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• v.10 no.5
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• pp.147-151
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• 2009

For integrated passive device (IPD) applications, we have successfully developed and characterized metalinsulator-metal (MIM) capacitors with 2000 $\AA$ plasma-enhanced chemical vapor deposition (PECVD) silicon nitride which are deposited with the $SiH_4/NH_3$ gas mixing rate, working pressure, and RF power of PECVD at $250^{\circ}C$. Five PECVD process parameters are designed to lower the refractive index and lower the deposition rate of $Si_3N_4$ films for the high breakdown electric field. For the PECVD process condition of gas mixing rate (0.957), working pressure (0.9 Torr), and RF power (60 W), the atomic force microscopy (AFM) root mean square (RMS) value of about 2000 $\AA$ $Si_3N_4$ on the bottom metal is lowest at 0.862 nm and the breakdown electric field is highest at about 8.0 MV/cm with a capacitance density of 326.5 pF/$mm^2$. A pretreatment of metal electrodes is proposed, which can reduce the peeling of nitride in the harsh test environment of heat, pressure, and humidity.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.60.2-60.2
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• 2011

본 연구에서는 Indium-free 및 gallium-free 기반의 산화물 TFT를 제작하기 위해 n-type $TiO_2$ 반도체 기반의 thin film transistor ($Mo/TiO_{2-x}/SiO_2/p+\;+Si$)를 oxygen deficient black $TiO_{2-x}$ 타겟을 이용하여 DC magnetron sputtering 공법으로 제작하고 그 특성을 분석하였다. DC magnetron sputtering 공법으로 성막된 $TiO_{2-x}$ semiconductor의 전기적, 광학적, 화학적 결합 에너지 및 구조적 특성 분석을 위해 semiconductor parameter analyzer (Aglient 4156-C), UV/Vis spectrometer, X-ray Photoelectron Spectroscopy, Transmission Electron Microscopy를 각각 이용하여 분석하였으며 이를 RTA 전/후 특성 비교를 통하여 관찰하였다. $TiO_{2-x}$ TFT의 소자 특성은 RTA 열처리 전/후 전형적인 insulator 특성에서 semiconductor 특성으로 변화되는 것을 관찰할 수 있었으며, 최적화된 열처리 공정에서 filed effect mobility 0.69 $cm^2$/Vs, on to off current ratio $2.04{\times}10^7$, sub-threshold swing 2.45 V/decade와 Vth 10.45 V를 확보할 수 있었다. 또한 RTA 열처리 후 밴드갭이 3.25에서 3.41로 확장되는 특성을 나타내었다. 특히 RTA 열처리 후 stoichiometric $TiO_2$ 상태와는 다른 $Ti^{2+}$, $Ti^{3+}$, $Ti^{4+}$ 등의 다양한 oxidation states가 관찰되었으며 이러한 oxidation states를 $TiO_{2-x}$ 박막에서의 oxygen deficient 상태와 연관시킴으로써 oxygen vacancy의 n-type dopant로의 거동을 확인하였다. $TiO_2$ 채널 기반의 TFT 특성을 통하여서 indium free 또는 gallium free 산화물 채널로써의 가능성을 확인하였다.

• Electrical & Electronic Materials
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• v.10 no.7
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• pp.692-699
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• 1997

The silicon doped $Al_{0.33}$G $a_{0.67}$As were grown by molecular beam epitaxy. The electroreflectance(ER) spectra of Schottky barrier Au/n-Al/suu x/G $a_{1-x}$ As have been measured at various modulation voltage( $V_{ac}$ ) and dc bias voltage( $V_{bias}$). From the observed Franz-Keldysh oscillations(FKO) peak, the band gap energy of the $Al_{x}$G $a_{1-x}$ As is 1.91 eV which corresponds to an Al composition of 33%. The internal electric field( $E_{i}$)of this sample is 2.96$\times$10$^{5}$ V/cm. As the modulation voltage( $V_{ac}$ ) is changed, the line shape of ER signal does not change but its amplitude varies linearly. The amplitude as a function of modulation voltage has saturated at 0.8 V. The internal electric field has decreased from 6.47$\times$10$^{5}$ V/cm to 2.00$\times$10$^{5}$ V/cm as the dc bias voltage( $V_{bias}$) increases from -3.5 V to +0.8 V. The values of built-in voltage( $V_{bi}$ ) and carrier concentration(N) determined from the plot of $V_{bias}$ from the plot of $V_{bias}$ versus $E_{i}$$^{2}$ are 0.855 V and 3.83$\times$10$^{17}$ c $m^{-3}$ , respectively.ively.y.y.y.

• 한국정보디스플레이학회:학술대회논문집
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• 2007.08b
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• pp.1298-1300
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• 2007

The interface between SiNx and ZnO was investigated with Near Edge X-ray Absorption Fine Structure (NEXAFS) for ZnO based thin film transistor (TFT) applications. Impurity species were interstitial $N_2$ molecules at the SiNx / ZnO interface. The evolution of $N_2$ is decreased with increasing of anneal temperature.

• Journal of the Korean Magnetics Society
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• v.5 no.5
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• pp.511-514
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• 1995

The crystallization kinetics of $Fe_{73.5}Si_{13.5}B_{9}Cu_{1}Nb_{3}$ amorphous alloy has been investigated using differential scanning calorimetry (DSC). The crystallization process had two stages, i.e. precipitation of the $\alpha$-Fe(Si) solid solution and the tetragonal borides. The isothermal transformation data of the amorphous alloy has been fitted successfully to the generalized Johnson-Mehl-Avrami equation. The mean time exponent, n, obtained is close to 2.5. The value of n=2.5 may be interpreted as being due to a diffusion-controlled transformation process with a constant nucleation rate, one likely transformation mode for the crystallization of metallic amorphous alloys. The activation energy of the overall crystallization process deduced from the time to 50% crystallization are about 81 kcal/mole. The value is of the same order as those estimated from viscous flow.

• Proceedings of the IEEK Conference
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• 2000.06b
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• pp.115-118
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• 2000

Uncooled pyroelectric infrared detectors based on BST(B $a_{-x}$S $r_{x}$Ti $O_3$) thin films have been fabricated by RF magnetron sputtering and surface Micromachining technology. The detectors form BST thin film ferroelectric capacitors grown by RF magnetron sputtering on N/O/N(S $i_3$ $N_4$/ $SiO_2$/S $i_3$ $N_4$) membrane. The sputtered BST thin film exhibits highly c-axis oriented crystal structure that no poling treatment for sensing applications is required. This is an essential factor to increase the yield for realization of an infrared image sensor. surface-Micromachining technology is used to lower the thermal mass of the detector by giving maximum sensor efficiency Gold-black is evaporated on top of the sensing elements used the thermal evaporator. fabricated uncooled pyroelectric infrared detectors is highly output voltage at the low temperature(1$^{\circ}C$).).).

• Korean Journal of Materials Research
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• v.9 no.10
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• pp.1012-1017
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• 1999

Low resistance ohmic contacts to the Si-doped $\textrm{In}_{0.17}\textrm{Ga}_{0.83}\textrm{N}$(~$\times10^{19}\textrm{cm}^{-3}$) were obtained using the W metallization schemes. Specific contact resistance decreased with increasing annealing temperature. The lowest resistance is obtained after a nitrogen ambient annealing at $950^{\circ}C$ for 90 s, which results in a specific contact resistance of $2.75\times10^{-8}\Omega\textrm{cm}^{-3}$. Interfacial reactions and surface are analyzed using x-ray diffraction and scanning electron microscopy (SEM). The X-ray diffraction results show that the reactions between the W film and the $\textrm{In}_{0.17}\textrm{Ga}_{0.83}\textrm{N}$ produce a $\beta$-$W_2N$ phase at the interface. The SEM result shows that the morphology of the contacts is stable up to a temperature as high as $850^{\circ}C$. Possible mechanisms are proposed to describe the annealing temperature dependence of the specific contact resistance.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.48 no.6
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• pp.410-415
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• 1999

$Ba_{1-x}Sr_xTiO_3$ thin films with various ratio of Sr (X = 0.4, 0.5, 0.6) were grown $Pt/TiN/SiO_2/Si$ subastrate by RF magnetron sputtering deposition. As, Ag, and Cu films were deposited on $Ba_{1-x}Sr_xTiO_3$ thin films as top electrodes by using a thermal evaporator. The electrical properties of $Ba_{1-x}Sr_xTiO_3$ thin films for various compositions were characterized and the physical properties at interface between $Ba_{1-x}Sr_xTiO_3$ thin films and top electrodes were evaluated in terms of the work function difference. At x =0.5, the degradation of capacitance is lower to the other compositions. As negative biasapplied, the specimen with Cu top electrode has board saturation region and low leakage current since work function of Cu is bigger than other electrodes.$ Ba_{0.5}Sr_{0.5}TiO_3$ thin films with Cu top electrode, the dielectric constant was measured to the value of 354 at 1 kHz and the leakage current was obtained to the value of $5.26\times10^{-6}A/cm2$ at the forward bias of 2 V.

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.26-26
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• 2000

High quality epitaxial Y2O3 thin films were prepared on Si(111) and (001) substaretes by using ion beam assisted deposition. As a substrate, clean and chemically oxidized Si wafers were used and the effects of surface state on the film crystallinity were investigated. The crystalline quality of the films were estimated by x-ray scattering, rutherford backscattering spectroscopy/channeling, and high-resolution transmission electron microscopy (HRTEM). The interaction between Y and Si atoms interfere the nucleation of Y2O3 at the initial growth stage, it could be suppressed by the interface SiO2 layer. Therefore, SiO2 layer of the 4-6 layers, which have been known for hindering the crystal growth, could rather enhance the nucleation of the Y2O3 , and the high quality epitaxial film could be grown successfully. Electrical properties of Y2O3 films on Si(001) were measured by C-V and I-V, which revealed that the oxide trap charge density of the film was 1.8$\times$10-8C/$\textrm{cm}^2$ and the breakdown field strength was about 10MV/cm.