• 한국전기전자재료학회논문지
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• 제33권1호
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• pp.25-30
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• 2020

Oxide (SiO₂)/Metal(Ag)/Oxide(SiO₂, ITO, ZnO) multilayer films were fabricated using a magnetron sputtering technique at room temperature on Si (p-type, 100) and a glass substrate. The electrical and optical properties of the asymmetric multilayer films depended on the thickness of the mid-layer film and the type of oxide in the bottom layer. As the metal layer becomes thicker, the sheet resistance decreases. However, the transmittance decreases when the metal layer exceeds a threshold thickness of approximately 10~12 nm. In addition, the sheet resistance and transmittance change according to the type of oxide in the bottom layer. If the oxide has a large resistivity, the overall sheet resistance increases. In addition, the anti-reflection effect changes according to the refractive index of the oxide material. The optical and electrical properties of multilayer films were investigated using an ultraviolet visible (UV-Vis) spectrophotometer and a 4-point probe, respectively. The optimum structure is SiO₂ (30 nm)/Ag (10 nm)/ZnO (30 nm) multilayer, with the highest FOM value of 7.7×10^-3 Ω^-1.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2009년도 추계학술발표대회
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• pp.49.2-49.2
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• 2009

투명전극은 디스플레이, 태양전지와 같은 광전자 소자에 필수적이며, 지금까지 개발된 재료 중에는 ITO가 가장 투명하면서 전기전도도가 높고 생산성도 좋기 때문에 투명전극의 재료로 사용하고 있다. ITO는 낮은 비저항(${\sim}10^{-4}{\Omega}cm$) 과 높은 투과율 (~85 %), 상대적으로 넓은 밴드갭 에너지 (3.5 eV) 의특성과 같이 뛰어난 전기적 광학적 특성에 반해서 높은 원자재 가격, 불안정한 공급량 등으로 인한 문제점이꾸준히 제기되고 있다. 따라서 $In_2O_3$:Sn, ZnO:Al, ZnO:Ga, ZnO:F, ZnO:B, TiN 등과 같은 물질들로대체하려는 연구가 활발하게 진행되고 있다. ZnO는 ITO보다원자재의 수급이 원활하기 때문에 원가가 낮으며, 상대적으로 낮은 온도에서도 제작이 가능하다. 또한 화학적으로 안정적이므로 ZnO에 Al, Ga 등의 3족 원소를 도핑함으로써 낮은 비저항의 박막 제작이 가능하고, ITO 박막과 비교하여 etching이 쉬우며 기판과의 접착성이 좋으며, sputtering 공정시 plasma 분위기에서의 안정성이 뛰어나고 박막증착율이 높기 때문에 투명전극으로 적합한 재료이다. 본 연구에서는 cylindrical type의 Aldoping된 ZnO single target을 사용하여 박막 증착 압력의 변화를 주어 유리기판 위에 DC sputtering을 하였다. Fieldemission scanning electron microscope (FESEM)을 통해 ZnO:Al 박막의 표면의 형상과 두께를 확인하였으며, X-ray diffraction (XRD) 분석을 통해 박막의 결정학적 특성을 관찰하였다. 투명전극용 물질로서 ZnO:Al 박막의 적합성 여부를 확인하기 위하여 Van der Pauw 방법을 이용하여 박막의 비저항, 전자 이동도, 캐리어 농도를 측정하였으며, 박막의 기계적 성질 및 표면 접착성을 확인하기 위하여 nano-indentaion 분석을 하였다. 또한 UV-vis spectrophotometer를 이용하여 ZnO:Al 박막의 투과율을 분석하여 투명전극으로의 응용 가능성을 확인하였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 하계학술대회 논문집
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• pp.331-331
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• 2009

Hafnium oxide ($HfO_2$) attracted by one of the potential candidates for the replacement of si-based oxides. For applications of the high-k gate dielectric material, high thermodynamic stability and low interface-trap density are required. Furthermore, the amorphous film structure would be more effective to reduce the leakage current. To search the gate oxide materials, metal-insulator-metal (MIM) capacitors was fabricated by pulsed laser deposition (PLD) on indium tin oxide (ITO) coated glass with different oxygen pressures (30 and 50 mTorr) at room temperature, and they were deposited by Au/Ti metal as the top electrode patterned by conventional photolithography with an area of $3.14\times10^{-4}\;cm^2$. The results of XRD patterns indicate that all films have amorphous phase. Field emission scanning electron microscopy (FE-SEM) images show that the thickness of the $HfO_2$ films is typical 50 nm, and the grain size of the $HfO_2$ films increases as the oxygen pressure increases. The capacitance and leakage current of films were measured by a Agilent 4284A LCR meter and Keithley 4200 semiconductor parameter analyzer, respectively. Capacitance-voltage characteristics show that the capacitance at 1 MHz are 150 and 58 nF, and leakage current density of films indicate $7.8\times10^{-4}$ and $1.6\times10^{-3}\;A/cm^2$ grown at 30 and 50 mTorr, respectively. The optical properties of the $HfO_2$ films were demonstrated by UV-VIS spectrophotometer (Scinco, S-3100) having the wavelength from 190 to 900 nm. Because films show high transmittance (around 85 %), they are suitable as transparent devices.

• 한국전기전자재료학회논문지
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• 제20권1호
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• pp.80-85
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• 2007

We report the electro-optical properties of the sensory rhodopsin II using a near-field scanning microwave microscope(NSMM). Rhodopsin was known as a photoreceptor pigment with a retinal as a chromophore via a protonated Schiff base and consists of seven ${\alpha}-helical$ transmembrane segments. The sensory rhodopsin II, expressing E. coli UT5600 with endogenous retinal biosynthesis system and purified with $Ni^{-2}-NTA$ affinity chromatography in the presence of 0.02 % DM (Dodecyl Maltoside) from Natronomonas pharaonis. We measured the absorption spectra and the transients difference of sensory rhodopsin II from Natronomonas pharaonis using a UV/VIS spectrophotometer with Nd-Yag Laser (532 nm). The absorption spectra of NpSR II showed a typical rhodopsin spectrum with a left shoulder region and the photointermediates spectra of NpSR II-ground state (${\lambda}max=498\;nm$), NpSR II-M state (${\lambda}max=390\;nm$), and NpSR II-O state (${\lambda}max=550\;nm$) during the photocycle. The observed photocycle reaction was confirmed by measuring the microwave reflection coefficient $S_{11}$ at an operating frequency of f=3.93-3.95 GHz and compared with the results of a photocycle of NpSR II.

• 센서학회지
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• 제21권6호
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• pp.395-401
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• 2012

The bond strength of three types of $TiO_2$ coatings onto fluorine-doped $SnO_2$ (FTO) glass was investigated with the aid of a tape test according to ASTM D 3359-95. Transmittance was then measured using an UV-vis spectrophotometer in the wavelength range of 300 nm to 800 nm to evaluate the extent of adhesion of $TiO_2$ nanorods/nanoparticles on FTO glass. A sharp interface between the coating layer and the substrate was observed for single $TiO_2$ coating ($TiO_2$ nanorods/FTO glass), which may be detrimental to the bonding strength. In multicoating sample ($TiO_2$ nanorod/$TiO_2$ nanoparticle/$TiO_2$ nanoparticle/FTO glass), the tape test was not performed due to severe peeling-off prior to the test. On the other hand, the dual coating sample ($TiO_2$ nanorod/$TiO_2$ nanoparticle/FTO glass) showed minimum variation of transmittance (4%) after the test, suggesting that the topcoat adheres well with the FTO substrate due to the presence of the $TiO_2$ nanoparticle buffer layer. The use of a $TiO_2$ nanorod electrode layer with good adhesion may be attributed to the excellent dye sensitized solar cell performance.

• 펄프종이기술
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• 제47권1호
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• pp.59-65
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• 2015

In this study, we evaluated optimum condition of enzyme with pH and temperature for preparation of microfibillated cellulose(MFC). Well-known endo-glucanase, three enzymes were used and CMC was used for substrate. Enzyme activity was evaluated using DNS method and absorbance with UV/VIS spectrophotometer. The enzyme shown the greatest activity was reacted with pulps at optimum condition for 1 hour and treated pulps beated until 100 mL CSF. Enzyme B and Enzyme L was the higher enzyme activity below 0.1% concentration and Enzyme N was the lowest enzyme activity. At various pH and temperature conditions, enzyme activity of Enzyme B was higher than the others at the same concentration. Especially enzyme activity at $50^{\circ}C$ of Enzyme B was almost not changed over pH 6.0. Optimum condition of three enzyme was pH 6 or pH 7 and $50^{\circ}C$ or $60^{\circ}C$. Also beating efficiency of enzyme treated pulps with Enzyme B is 55.6%.

• 한국세라믹학회지
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• 제48권4호
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• pp.298-302
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• 2011

This study developed a pigment by doping Cr to Pyrochlore-type stannate crystals and investigated the chromogenic relationship in a glaze. Crystal phases of the pigment according to firing temperatures were analyzed by XRD, and the doping relationship was analyzed by Raman Spectroscopy. Color and reflection rate of the pigment were measured by UV-vis Spectrophotometer. Consequently, stannate characteristic band appeared at 307, 408, 505 and $755cm^{-1}$ until 0.1 mole substitution of $Cr_2O_3$. However, as amount of $Cr_2O_3$ increased, the stannate characteristic peak was decreased and shift happened at the left hand side due to Cr-dope. In composition of 0.12~0.14 mole substituted, the unreacted $Cr_2O_3$ stannate characteristic peak, which was not engaged, was shown. This result shows the maximum limit of solid solution was 0.1 mole $Cr_2O_3$. The color of the glaze, which was produced by adding 6 wt% of $Y_2Sn_{1.94}Cr_{0.06}O_7$ pigment in a lime or a lime-magnesia glaze and fired the mixture at $1260^{\circ}C$, was grayish pink with $L^*$ 70.29, $a^*$ 5.68 and $b^*$ 6.27. It showed gray with $L^*$ 68.82, $a^*$ 3.07and $b^*$ 8.13 for $Y_2Sn_{1.9}Cr_{0.1}O_7$.

• 한국전기전자재료학회논문지
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• 제21권7호
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• pp.629-637
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• 2008

We report several experimental data capable of evaluating the amorphous-to-crystalline (a-c) phase transformation in $(Ag)_x(Ge_2Sb_2Te_5)_{1-x}$ (x = 0, 0.05, 0.1) thin films prepared by a thermal evaporation. The isothermal a-c structural phase changes were evaluated by XRD, and the optical transmittance was measured in the wavelength range of $800{\sim}3000$ nm using a UV-vis-IR spectrophotometer. A speed of the a-c transition was evaluated by detecting the reflection response signals using a nano-pulse scanner with 658 nm laser diode (power P = $1{\sim}17$ mW, pulse duration t = $10{\sim}460$ ns). The surface morphology and roughness of the films were imaged by AFM. It was found that the crystallization speed was so enhanced with an increase of Ag content. While the sheet resistance of c-phase $(Ag)_x(Ge_2Sb_2Te_5)_{1-x}$ was similar to that of c-phase $Ge_2Sb_2Te_5$ (i.e., $R_c{\sim}10{\Omega}/{\square}$), the sheet resistance of a-phase $(Ag)_x(Ge_2Sb_2Te_5)_{1-x}$ was found to be lager than that of a-phase $Ge_2Sb_2Te_5$, $R_a{\sim}5{\times}10^6{\Omega}{/\square}$. For example, the ratios of $R_a/R_c$ for $Ge_2Sb_2Te_5$ and $(Ag)_{0.1}(Ge_2Sb_2Te_5)_{0.9}$ were approximately $5{\times}10^5$ and $5{\times}10^6$, respectively.

• 한국전기전자재료학회논문지
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• 제30권5호
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• pp.294-300
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• 2017

$TeO_x$ thin films were deposited at various $O_2$/Ar gas-flow ratios by a reactive RFmagneton sputtering technique from $TeO_2$ and Te targets. X-ray diffraction (XRD) results revealed that the $TeO_x$ thin films were amorphous. The structure and chemical composition of the $TeO_x$ thin films were investigated by fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). The optical characteristics of the $TeO_x$ thin films were investigated by an Ellipsometer and a UV-VIS-NIR spectrophotometer. According to the $O_2$/Ar gas-flow ratios, the atomic composition ratio of $TeO_x$ thin films was divided into two regions(x=1-2, 2-3). Different optical characteristics were shown in each region. With an increasing $O_2$/Ar gas-flow ratio, the refractive index of the $TeO_x$ thin films decreased and the optical bandgap of the films increased.

• 한국전기전자재료학회논문지
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• 제30권3호
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• pp.133-138
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• 2017

We evaluated the structural, electrical and optical properties of tungsten (W)-doped $Ge_8Sb_2Te_{11}$ thin films. In a previous work, GeSbTe alloys were doped with different materials in an attempt to improve thermal stability. 200 mm thick $Ge_8Sb_2Te_{11}$ and W-doped $Ge_8Sb_2Te_{11}$ films were deposited on p-type Si (100) and glass substrates using a magnetron co-sputtering system at room temperature. The fabricated films were annealed in a furnace in the $0{\sim}400^{\circ}C$ temperature range. The structural properties were analyzed using X-ray diffraction (X'pert PRO, Phillips). The results showed increased crystallization temperature ($T_c$) leading to thermal stability in the amorphous state. The optical properties were analyzed using an UV-Vis-IR spectrophotometer (Shimadzu, U-3501, range : 300~3,000 nm). The results showed an increase in the crystalline material optical energy band gap ($E_{op}$) and an increase in the $E_{op}$ difference (${\Delta}E_{op}$). This is a good effect to reduce memory device noise. The electrical properties were analyzed using a 4-point probe (CNT-series). This showed increased sheet resistance ($R_s$), which reduces programming current in the memory device.