• 한국전기전자재료학회논문지
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• 제21권10호
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• pp.923-929
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• 2008

On the piezoelectric polymer, PVDF (poly vinylidene fluoride), the transparent conducting oxide (TCO) electrode material thin film was deposited by roll to roll sputtering process mentioned as a mass product-friendly process for display application. The deposition method for ITO Indium Tin Oxides) as our TCO was DC magnetron sputtering optimized for polymer substrate with the low process temperature. As a result, a high transparent and good conductive ITO/PVDF film was prepared. During the process, especially, the gas mixture ratio of Ar and Oxygen was concluded as an important factor for determining the film's physical properties. There were the optimum ranges for process conditions of mixture gas ratio for ITO/PVDF From these results, the doping mechanism between the oxygen atom and the metal element, Indium or Tin was highly influenced by oxygen partial pressure condition during the deposition process at ambient temperature, which gives the conductivity to oxide electrode, as generally accepted. With our studies, the process windows of TCO for display and other application can be expected.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.199-199
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• 2011

Recently, Thin film transistors (TFTs) with amorphous oxide semiconductors (AOSs) can offer an important aspect for next generation displays with high mobility. Several oxide semiconductor such as ZnO, $SnO_2$ and InGaZnO have been extensively researched. Especially, as a well-known binary metal oxide, tin oxide ($SnO_2$), usually acts as n-type semiconductor with a wide band gap of 3.6eV. Over the past several decades intensive research activities have been conducted on $SnO_2$ in the bulk, thin film and nanostructure forms due to its interesting electrical properties making it a promising material for applications in solar cells, flat panel displays, and light emitting devices. But, its application to the active channel of TFTs have been limited due to the difficulties in controlling the electron density and n-type of operation with depletion mode. In this study, we fabricated staggered bottom-gate structure $SnO_2$-TFTs and patterned channel layer used a shadow mask. Then we compare to the performance intrinsic $SnO_2$-TFTs and doping hafnium $SnO_2$-TFTs. As a result, we suggest that can be control the defect formation of $SnO_2$-TFTs by doping hafnium. The hafnium element into the $SnO_2$ thin-films maybe acts to control the carrier concentration by suppressing carrier generation via oxygen vacancy formation. Furthermore, it can be also control the mobility. And bias stability of $SnO_2$-TFTs is improvement using doping hafnium. Enhancement of device stability was attributed to the reduced defect in channel layer or interface. In order to verify this effect, we employed to measure activation energy that can be explained by the thermal activation process of the subthreshold drain current.

• 한국재료학회지
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• 제15권7호
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• pp.453-457
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• 2005

Piezoelectric properties of $Pb(Mn_{1/3}Nb_{2/3})O_3-PbZrO_3-PbTiO_3$ ceramics were investigated with $Al_2O_3$ content $(0.0-1.0 wt\%)$. The constituent phases, microstructure, electromechanical coupling factor, dielectric constant, piezoelectric charge and voltage constants were analyzed. Diffraction peaks for (002) and (200) planes were identified by X-ray diffractometer for all the specimens doped with $Al_2O_3$, indicating the MPB (morphotropic phase boundary) composition of tetragonal structures. The highest sintered density of $7.8 g/cm^3$ was obtained for $0.2wt\%\;Al_2O_3-doped$ specimen. Grain size increased by doping $Al_2O_3$ up to $0.3 wt\%$, and it decreased by more doping. Electromechanical coupling factor, dielectric constant, piezoelectric charge and voltage constants increased by doping $Al_2O_3$ up to $0.2wt\%$, and it decreased by more doping. This might result from the formation of oxygen vacancies due to defects in $O^{2-}$ ion sites and the substitution of $Al^{3+}$ ions.

• Current Applied Physics
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• 제18권11호
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• pp.1422-1425
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• 2018

$NaTa_{1-x}Fe_xO_3$ ($0{\leq}x{\leq}0.40$) nanocubes were synthesized by a relatively low temperature hydrothermal method, using $Ta_2O_5$, $FeCl_3$ and NaOH as the precursors. The UV-vis diffuse reflectance spectra showed that $NaTa_{1-x}Fe_xO_3$ had significant visible-light-absorbing capability, and the absorption edge of $NaTaO_3$ shifted to longer wavelength with the increase of Fe dopants. Moreover, $NaTa_{1-x}Fe_xO_3$ exhibited room-temperature ferromagnetism when $Fe^{3+}$ occupied $Ta^{5+}$ sites in $NaTaO_3$ crystal lattice. The ferromagnetism is mainly attributed to the superexchange interactions between doped $Fe^{3+}$, rather than the contribution of oxygen vacancies caused by Fe doping. Therefore, Fe doping can simultaneously regulate the optical and magnetic properties of $NaTaO_3$ semiconductor, which will enable its potential applications in multifunctional optical-electronics and opticalspintronics devices.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 춘계학술대회 초록집
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• pp.74.2-74.2
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• 2010

유리를 기판으로 하는 실리콘 박막태양전지의 경우 PIN 비정질 태양전지 뒤에 후면반사막으로 주로 Ga 또는 Al이 Doping된 후면반사막을 사용한다. 이 후면반사막의 경우 PIN층을 통과한 빛을 반사함으로써 빛의 효용성을 높이는 데 그 목적이 있다. 본 논문에서는 후면박사막으로 ZnO:Al을 사용하고 산소 부여량에 따른 투과도, 비저항 변화를 살펴보고 실제로 a-Si:H 박막태양전지를 제작하여 그 효과를 파악하였다. 이 때 산소 부여량이 많아질 경우 투과도는 높아지지만 비저항이 급격히 높아지는 문제가 있었으나 이 조건으로 a-Si:H 박막태양전지를 제작시에도 효율이 상승하였다.

• 태양에너지
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• 제19권1호
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• pp.29-36
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• 1999

ZnO/n-Si junctions were fabricated by spin coating with ZnO precursor produced by the sol-gel process. In order to increase the electrical conductivity of ZnO films, the films were n-doped with Al impurity and subsequently annealed at about $450^{\circ}C$ under reducing environments. The ohmic contacts between n-Si and AI for a bottom electrode were successfully fabricated by doping the rear surface of Si substrate with phosphorous atoms. The front surface of the substrate was also doped with phosphorous atoms for improving the efficiency of the solar cells. Consequently, conversion efficiencies ranging up to about 5.3% were obtained. These efficiencies were found to decrease slowly with time because of the oxide films formed at the ZnO/Si interface upon oxygen penetration through the porous ZnO. Oxygen barrier layers could be necessary in order to prevent the reduction of conversion efficiencies.

• Bulletin of the Korean Chemical Society
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• 제20권9호
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• pp.1045-1048
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• 1999

Electronic structures calculated based upon the extended Huckel tight-binding method for Ba1-xKxBiO3 with x = 0, 0.04, and 0.4 are reported. It is noticed that the commensurate ordering of Bi 3+ and Bi 5+ is responsible for the insulating and semiconducting behavior in BaBiO3 and Ba0.96K0.04BiO4. The band gaps of 3.2 eV and 1.4 eV for the former and the latter compounds, respectively, are consistent with the experimental results. Doping in Bi 6s-block band up to x = 0.4 causes the collapse of the ordering of Bi 3+ and Bi 5+, thereby resulting in the superconductivity in the Ba0.6K0.4BiO3 compound. Strikingly, the character of oxygen contributes to the conducting mechanism than that of the bismuth. This is quite different from the cuprate superconductors in which the character of copper dominates that of oxygen.

• Journal of Ceramic Processing Research
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• 제13권spc2호
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• pp.359-362
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• 2012

We have employed Kelvin force microscopy (KFM) system to measure the potential change of a single SnO2 nanowire which had been synthesized on the Au thin film by a thermal process. By using the KFM probing technique, Rh coated conducting cantilever can approach a single SnO2 nanowire in nano scale and get the potential images with oscillating AC bias between Au electrode and cantilever. Also, during imaging the potential status, we controlled the concentration of oxygen in measuring chamber to change the ionosorption rate. From the results of such experiments, we verified that the surface potential as well as doping type of a single SnO2 nanowire could be changed by oxygen ionosorption.

• 청정기술
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• 제23권3호
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• pp.308-313
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• 2017

본 연구에서는 Graphite Felt (GF) 전극의 표면에 산소와 질소의 도핑을 통하여 전기화학적 특성을 개선하고, 이의 촉매화학적 효과를 바나듐 레독스 흐름전지의 양극과 음극의 특성비교를 통하여 관찰하였다. 탄소전극 표면의 산소와 질소 동시 도핑은 GF 샘플을 773 K에서 암모니아-공기 ($NH_3=50%$, $O_2=10%$) 혼합가스에 노출시켜 Chemical Vapor Deposition (CVD) 방법으로 제조하였다. 이러한 산소-질소 동시 도핑의 전기화학적 효과는 산소만으로 도핑 처리된 GF 샘플과 비교하여 분석, 평가하였다. 탄소전극 샘플들의 표면 구조와 화학적 조성은 Scanning Electron Microscopy (SEM)와 X-ray Photoelectron Spectroscopy (XPS) 방법을 통하여 분석하였다. 결과물로 얻어진 탄소전극은 바나듐 레독스-흐름전지의 양극과 음극에 동시 적용하여 충-방전 사이클을 진행하고, 각 전극이 흐름전지의 효율과 양극과 음극에서의 전기화학적 특성에 미치는 효과를 비교하여 분석하였다. 산소와 질소의 동시 도핑으로 처리된 GF 전극은 산소만으로 활성화된 전극에 비하여 흐름전지의 전압 및 에너지 효율에서 2% 이상의 향상 효과를 보여주었다. 특히, 탄소전극 표면의 산소-질소의 동시 도핑은 음극반응에서 우수한 전기화학적 특성을 유도하는 것을 확인하였다.

• Bulletin of the Korean Chemical Society
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• 제35권6호
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• pp.1613-1618
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• 2014

Perovskite-type oxides are promising oxygen carriers in producing oxygen-enriched $CO_2$ gas stream for oxyfuel combustion. In this study, a new series of $SrCo_{1-x}Fe_xO_{3-{\delta}}$ (x = 0.2, 0.4, 0.6, 0.8) was prepared and used to produce $O_2/CO_2$ mixture gas. The phase, crystal structure, and morphological properties of $SrCo_{1-x}Fe_xO_{3-{\delta}}$ were investigated through X-ray diffraction, specific surface area measurements, and environmental scanning electron microscopy. The oxygen desorption performance of $SrCo_{1-x}Fe_xO_{3-{\delta}}$ was studied in a fixed-bed reactor system. Results showed that the different x values of $SrCo_{1-x}Fe_xO_{3-{\delta}}$ have no obvious effects on crystalline structure. However, the oxygen desorption performance of $SrCo_{1-x}Fe_xO_{3-{\delta}}$ is improved by Co doping. Moreover, $SrCo_{0.8}Fe_{0.2}O_{3-{\delta}}$ synthesized via a new EDTA method has a larger BET surface area ($40.396m^2/g$), smaller particle size (48.3 nm), and better oxygen production performance compared with that synthesized through a liquid citrate method.