• Korean Journal of Materials Research
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• v.17 no.4
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• pp.232-235
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• 2007

Indium tin oxide (ITO) films were deposited on polycarbonate CR39 substrate using DC magnetron sputtering. ITO thin films were deposited at room temperature because glass-transition temperature of CR39 substrate is $130^{circ}C$ ITO thin films are used as bottom and top electrodes and for organic thin film transparent transistor (OTFT). The electrodes electrical properties of ITO thin films and their optical transparency properties in the visible wavelength range (300-800 nm) strongly depend on the volume of oxygen percent. The optimum resistivity and transparency of ITO thin film electrode was achieved with a 75 W plasma power, 10 % volume of oxygen and a 27 nm/min deposition rate. Above 85% transparency in the visible wavelength range (300-800 nm) was measured without post annealing process, and resistivity as low as $9.83{\times}^{TM}10^{-4}{\Omega}$ cm was measured at thickness of 300 nm.

• Journal of the Korean institute of surface engineering
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• v.31 no.2
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• pp.109-116
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• 1998

Highly transparent conductive pure and fluorine-doped tin oxide(FT0, $SnO_2$ : F) films have been prepared by low pressure metal organic chemical vapor deposition (LP-MOCVD) from various mixtures of tetramethyitin(TMT) with oxygen or oxygen containing ozone. The properties of TO films have been changed with the variation of gases, flow rate, and substrate temperature. The nsing of oxygen containing ozone instead of pure oxygen, reduced substrate temperature by 100-$150^{\circ}C$ while maintaining same thickness. The films prepared by using ozone showed the resistivity in the range from $10^~2$ to $10^{~3}\Omega$cm, and the mobiiity from 10 to $14\textrm{cm}^2$/Vs. Fluorine-doped tin oxide films had properties such as the resistivity about $10^{-4}\Omega$cm, and the mobility from 14 to $19\textrm{cm}^2$/Vs.

• Journal of the Korean Ceramic Society
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• v.54 no.5
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• pp.413-421
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• 2017

In this work, we studied a fluorite structure oxides: Yttria stabilized zirconia, (YSZ); Gd doped $CeO_2$ (GDC); erbia stabilized $Bi_2O_3$ (ESB); Zr doped erbia stabilized $Bi_2O_3$ (ZESB); Ca doped erbia stabilized $Bi_2O_3$ (CESB) in the temperature range of 250 to $600^{\circ}C$ using electrochemical impedance spectroscopy (EIS). As is well known, grain boundary blocking effect was observed in YSZ and GDC. However, there is no grain boundary effect on ESB, ZESB, and CESB. The Nyquist plots of these materials exhibit a single arc at low temperature. This means that there is no space charge effect on ${\delta}-Bi_2O_3$. In addition, impedance data were analyzed by using the brick layer model. We indirectly demonstrate that grain boundary ionic conductivity is similar to or even higher than bulk ionic conductivity on cubic bismuth oxide.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.9
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• pp.710-712
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• 2011

In this study, we fabricate resistive switching random access memory (ReRAM) devices constructed with a Al/$HfO_2$/ITO structure on glass substrates and investigate their memory characteristics. The hafnium oxide thin film used as a resistive switching layer is sputtered at room temperature in a sputtering system with a cooling unit. The Al/$HfO_2$/ITO device exhibits bipolar resistive switching characteristics, and the ratio of the high resistance (HRS) to low resistance states (LRS) is more than 60. In addition, the resistance ratio maintains even after $10^4$ seconds.

• 한국신재생에너지학회:학술대회논문집
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• 2009.11a
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• pp.218-221
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• 2009

Solid oxide fuel cells (SOFCs), as high-temperature fuel cells, have various advantages. In some merits of SOFCs, high temperature operation can lead to the capability for internal reforming, providing fuel flexibility. SOFCs can directly use CH4 and CO as fuels with sufficient steam feeds. However, hydrocarbons heavier than CH4, such as ethylene, ethane, and propane, induce carbon deposition on the Ni-based anodes of SOFCs. In the case of the ethylene steam reforming reaction on a Ni-based catalyst, the rate of carbon deposition is faster than among other hydrocarbons, even aromatics. In the reformates of heavy hydrocarbons (diesel, gasoline, kerosene and JP-8), the concentration of ethylene is usually higher than other low hydrocarbons such as methane, propane and butane. It is importatnt that ethylene in the reformate is removed for stlable operation of SOFCs. A new methodology, termed post-reforming was introduced for removing low hydrocarbons from the reformate gas stream. In this work, activity tests of some post-reforming catalysts, such as CGO-Ru, CGO-Ni, and CGO-Pt, are investigated. CGO-Pt catalyst is not good for removing ethylene due to low conversion of ethylene and low selectivity of ethylene dehydrogenation. The other hand, CGO-Ru and CGO-Ni catalysts show good ethylene conversion, and CGO-Ni catalyst shows the best reaction selectivity of ethylene dehydrogenation.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.10
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• pp.83-90
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• 1998

The effects of dopant activation anneal on GOI (Gate Oxide Integrity) of MOS capacitor with amorphous silicon gate electrode were investigated. It was found that the amorphous silicon gate electrode was crystallized and the dopant atoms were sufficiently activated by activation anneal. The mechanical stress of gate electrode that reveals large compressive stress in amorphous state, was released with increase of anneal temperature from $700^{\circ}C$ to 90$0^{\circ}C$. The resistivity of gate electrode polycrystalline silicon film is decreased by the increase of anneal temperature. The reliability of thin gate oxide and interface properties between oxide and silicon substrate greatly depends on the activation anneal temperature. The charge trapping characteristics as well as oxide reliability are improved by the anneal of 90$0^{\circ}C$ compare to that of $700^{\circ}C$ or 80$0^{\circ}C$. Especially, the lifetimes of the thin gate oxide estimated by TDDB method is 3$\times$10$^{10}$ for the case of $700^{\circ}C$ anneal, is significantly increased to 2$\times$10$^{12}$ for the case of 90$0^{\circ}C$ anneal. Finally, the interface trap density is reduced with relaxation of mechanical stress of gate electrode.

• Journal of Industrial and Engineering Chemistry
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• v.68
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• pp.117-123
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• 2018

Recently, aqueous method has attracted lots of attention because it enables the solution-processed metal oxide thin film with high electrical properties in low temperature fabrication condition to various flexible devices. Focusing the development of aqueous route, many researchers are only focused on metal oxide materials. However, for expansive application of the aqueous-based metal oxide films, the systematic study of performance change with process variables for the development of aqueous-based metal oxide insulator film is urgently required. Here, we propose importance of process variables to achieve high electrical-performance metal oxide insulator based on the aqueous method. We found that the significant process variables including precursor solution temperature and humidity during the spincoating process strongly affect chemical, physical, and electrical properties of $AlO_x$ insulators. Through the optimization of significant variables in process, an $AlO_x$ insulator with a leakage current value approximately $10^5$ times smaller and a breakdown voltage value approximately 2-3 times greater than un-optimized $AlO_x$ was realized. Finally, by introducing the optimized $AlO_x$ insulators to solutionprocessed $InO_x$ TFTs, we successfully achieved $InO_x/AlO_x$ TFTs with remarkably high average field-effect mobility of ${\sim}52cm^2V^{-1}\;s^{-1}$ and on/off current ratio of 106 at fabrication temperature of $250^{\circ}C$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.11-11
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• 2010

Thin-film-transistors (TFTs) that can be deposited at low temperature have recently attracted lots of applications such as sensors, solar cell and displays, because of the great flexible electronics and transparent. Transparent and flexible transistors are being required that high mobility and large-area uniformity at low temperature [1]. But, unfortunately most of TFT structures are used to be $SiO_2$ as gate dielectric layer. The $SiO_2$ has disadvantaged that it is required to high driving voltage to achieve the same operating efficiency compared with other high-k materials and its thickness is thicker than high-k materials [2]. To solve this problem, we find lots of high-k materials as $HfO_2$, $ZrO_2$, $SiN_x$, $TiO_2$, $Al_2O_3$. Among the High-k materials, $Al_2O_3$ is one of the outstanding materials due to its properties are high dielectric constant ( ~9 ), relatively low leakage current, wide bandgap ( 8.7 eV ) and good device stability. For the realization of flexible displays, all processes should be performed at very low temperatures, but low temperature $Al_2O_3$ grown by sputtering showed deteriorated electrical performance. Further decrease in growth temperature induces a high density of charge traps in the gate oxide/channel. This study investigated the effect of growth temperatures of ALD grown $Al_2O_3$ layers on the TFT device performance. The ALD deposition showed high conformal and defect-free dielectric layers at low temperature compared with other deposition equipments [2]. After ITO was wet-chemically etched with HCl : $HNO_3$ = 3:1, $Al_2O_3$ layer was deposited by ALD at various growth temperatures or lift-off process. Amorphous InGaZnO channel layers were deposited by rf magnetron sputtering at a working pressure of 3 mTorr and $O_2$/Ar (1/29 sccm). The electrodes were formed with electron-beam evaporated Ti (30 nm) and Au (70 nm) bilayer. The TFT devices were heat-treated in a furnace at $300^{\circ}C$ and nitrogen atmosphere for 1 hour by rapid thermal treatment. The electrical properties of the oxide TFTs were measured using semiconductor parameter analyzer (4145B), and LCR meter.

• Electrical & Electronic Materials
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• v.9 no.8
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• pp.789-798
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• 1996

The double nitride layer Metal Nitride Oxide Semiconductor(MNOS) structures were fabricated by variating both gas ratio and nitride thickness, and by duplicating nitride deposited and one nitride layer MNOS structure to improve nonvolatile memory characteristics of MNOS structures by Low Pressure Chemical Vapor Deposition(LPCVD) method. The nonvolatile memory characteristics of write-in, erase, memory retention and degradation of Bias Temperature Stress(BTS) were investigated by the homemade automatic .DELTA. $V_{FB}$ measuring system. In the trap density double nitride layer structures were higher by 0.85*10$^{16}$ $m^{-2}$ than one nitride layer structure, and the AVFB with oxide field was linearly increased. However, one nitride layer structure was linearly increased and saturated above 9.07*10$^{8}$ V/m in oxide field. In the erase behavior, the hole injection from silicon instead of the trapped electron emission was observed, and also it was highly dependent upon the pulse amplitude and the pulse width. In the memory retentivity, double nitrite layer structures were superior to one nitride layer structure, and the decay rate of the trapped electron with increasing temperature was low. At increasing the number on BTS, the variance of AVFB of the double nitride layer structures was smaller than that of one nitride layer structure, and the trapped electron retention rate was high. In this paper, the double nitride layer structures were turned out to be useful in improving the nonvolatile memory characteristics.

• Applied Chemistry for Engineering
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• v.19 no.2
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• pp.236-241
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• 2008

The possibility of silicon oxidation through the aerial-diffusion of active oxygen species has been evaluated. The species originate from the surface of $TiO_2$ exposed by UV. Among process parameters such as UV intensity, substrate temperature and chamber pressure with oxygen, UV intensity was a major parameter to the influence on the oxide growth rate. When 1 kW high pressure Hg lamp was used as a UV source, the growth rate of silicon oxide was 8 times as faster as that of a 60 W BLB lamp. However, as the chamber pressure increased, the growth rate was declined due to the suppression of aerial diffusion of active oxygen species. According to the results, it could be confirmed that the aerial-diffusion of active oxygen species from UV-irradiated photocatalytic surface can be applied to a new method for preparing an ultra-thin silicon oxide at the range of relatively low temperature.