• Polymer(Korea)
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• v.34 no.1
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• pp.25-31
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• 2010

Polymer core and metal shell composite particles have been prepared by the electroless nickel plating on the surface of monodisperse polystyrene microspheres. Various sizes of polystyrene particles with highly monodisperse state could be synthesized by controlling the dispersion medium in dispersion polymerization. Electroless nickel plating was performed on the polystyrene particle with diameter of $3.4\;{\mu}m$. The morphology of polystyrene/nickel composite particles was investigated to see the effect of the plating conditions, such as the $PdCl_2$ and glycine concentrations and the dropping rate of nickel plating solution, on nickel deposition. With $PdCl_2$ and glycine concentrations at more than 0.4 g/L and 1 M, respectively, more uniform nickel layer and less precipitated nickel aggregates were formed. At the given plating time of 2 h, the same amount of plating solution was introduced by varying the dropping rate. Though the effect of dropping rate on particle morphology was not noticeable, the dropping rate of 0.15 mL/min for 60 min showed rather uniform plating.

• Journal of the Korean institute of surface engineering
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• v.29 no.6
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• pp.809-815
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• 1996

$Y_2O_3$-based metal-insulator-semiconductor (MIS) structure on p-Si(100) has been studied. Films were prepared by UHV reactive ionized cluster beam deposition (r-ICBD) system. The base pressure of the system was about $1 \times 10^{-9}$ -9/ Torr and the process pressure $2 \times 10^{-5}$ Torr in oxygen ambience. Glancing X-ray diffraction(GXRD) and in-situ reflection high energy electron diffracton(RHEED) analyses were performed to investigate the crystallinity of the films. The results show phase change from amorphous state to crystalline one with increasingqr acceleration voltage and substrate temperature. It is also found that the phase transformation from $Y_2O_3$(111)//Si(100) to $Y_2O_3$(110)//Si(100) in growing directions takes place between $500^{\circ}C$ and $700^{\circ}C$. Especially as acceleration voltage is increased, preferentially oriented crystallinity was increased. Finally under the condition of above substrate temperature $700^{\circ}C$ and acceleration voltage 5kV, the $Y_2O_3$films are found to be grown epitaxially in direction of $Y_2O_3$(1l0)//Si(100) by observation of transmission electron microscope(TEM). Capacitance-voltage and current-voltage measurements were conducted to characterize Al/$Y_2O_3$/Si MIS structure with varying acceleration voltage and substrate temperature. Deposited $Y_2O_3$ films of thickness of nearly 300$\AA$ show that the breakdown field increases to 7~8MV /cm at the same conditon of epitaxial growing. These results also coincide with XPS spectra which indicate better stoichiometric characteristic in the condition of better crystalline one. After oxidation the breakdown field increases to 13MV /cm because the MIS structure contains interface silicon oxide of about 30$\AA$. In this case the dielectric constant of only $Y_2O_3$ layer is found to be $\in$15.6. These results have demonstrated the potential of using yttrium oxide for future VLSI/ULSI gate insulator applications.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.120-120
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• 2011

Graphene is a carbon based material and it has great potential of being utilized in various fields such as electronics, optics, and mechanics. In order to develop graphene-based logic systems, graphene field-effect transistor (GFET) has been extensively explored. GFET requires supporting devices, such as volatile memory, to function in an embedded logic system. As far as we understand, graphene has not been studied for volatile memory application, although several graphene non-volatile memories (GNVMs) have been reported. However, we think that these GNVM are unable to serve the logic system properly due to the very slow program/read speed. In this study, a GVM based on the GFET structure and using an engineered graphene channel is proposed. By manipulating the deposition condition, charge traps are introduced to graphene channel, which store charges temporarily, so as to enable volatile data storage for GFET. The proposed GVM shows satisfying performance in fast program/erase (P/E) and read speed. Moreover, this GVM has good compatibility with GFET in device fabrication process. This GVM can be designed to be dynamic random access memory (DRAM) in serving the logic systems application. We demonstrated GVM with the structure of FET. By manipulating the graphene synthesis process, we could engineer the charge trap density of graphene layer. In the range that our measurement system can support, we achieved a high performance of GVM in refresh (>10 ${\mu}s$) and retention time (~100 s). Because of high speed, when compared with other graphene based memory devices, GVM proposed in this study can be a strong contender for future electrical system applications.

• Korean Journal of Materials Research
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• v.1 no.1
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• pp.46-53
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• 1991

The stress of PSG (Phosphosilicate glass), USG (Undoped-silicate grass) and SiN films, which are mainly used as passivation layers in semiconductor memory devices, deposited by CVD methods has been studied as a function of film thickness and holding time in air. The stress of the PSG film or the USG film is increased in tensile state with increasing film thickness. On the other hand the stress level of the SiN film in compressive stress does not change as film thickness changes. The stress of PSG film shows the drastic change from the tensile stress to the compressive stress after the film is left 2 days in air. FTIR spectra indicated that the stress variation was due to the penetration of water molecule. It looks possible to recover the stress of about $2.5{\times}{10^9}dyne/cm^2$ by annealing treatment at $300^{\circ}C$ for 20min. The total stress of multi-layered films having the PSG film is determined mainly by the stress variation of PSG layer with holding time. The total stress of multi-layered film appears to have a functional relationship with the stress in the thickness of each film. The resistance against stress-migration of sputtered Al line increases with increasing the tensile stress for the PSG film or the USG film.

• Journal of Animal Science and Technology
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• v.57 no.5
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• pp.17.1-17.6
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• 2015

The present study investigated the nutritional and economic suitability of cashew reject meal (full fat and defatted) as replacement for groundnut cake (GNC) in the diets of laying chickens. A total of eighty four brown shavers at 25 weeks of age were randomly allotted into seven dietary treatments each containing 6 replicates of 2 birds each. The seven diets prepared included diet 1, a control with GNC at $220gkg^{-1}$ as main protein source in the diet. Diets 2, 3 and 4 consist of gradual replacement of GNC with defatted cashew reject meal (DCRM) at 50%, 75% and 100% on weight for weight basis respectively while diets 5, 6 and 7 consist of gradual inclusion of full fat cashew reject meal (FCRM) to replace 25%, 35% and 50% of GNC protein respectively. Each group was allotted a diet in a completely randomized design in a study that lasted eight weeks during which records of the chemical constituent of the test ingredients, performance characteristics, egg quality traits and economic indicators were measured. Results showed that the crude protein were 22.10 and 35.4% for FCRM and DCRM respectively. Gross energy of DCRM was 5035 kcal/kg compared to GNC, 4752 kcal/kg. Result of aflatoxin $B_1$ revealed moderate level between 10 and $17{\mu}g/Kg$ in DCRM and GNC samples respectively. Birds on control gained 10 g, while those on DCRM and FCRM gained about 35 g and 120 g respectively. Feed intake declined (P < 0.05) with increased level of FCRM. Hen day production was highest in birds fed DCRM, followed by control and lowest value (P < 0.05) was recorded for FCRM. No significant change (P > 0.05) was observed for egg weight and shell thickness. Fat deposition and cholesterol content increased (P > 0.05) with increasing level of FCRM. The cost of feed per kilogram decreased gradually with increased inclusion level of CRM. The prediction equation showed the relative worth of DCRM compared to GNC was 92.3% whereas the actual market price of GNC triples that of DCRM. It was recommended that GNC could be completely replaced by DCRM in layer's diets in regions where this by product is abundant. However, FCRM should be cautiously used in diets of laying chickens.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.74-74
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• 2010

One-dimensional nanosturctures such as nanowires and nanotube have been mainly proposed as important components of nano-electronic devices and are expected to play an integral part in design and construction of these devices. Silicon carbide(SiC) is one of a promising wide bandgap semiconductor that exhibits extraordinary properties, such as higher thermal conductivity, mechanical and chemical stability than silicon. Therefore, the synthesis of SiC-based nanowires(NWs) open a possibility for developing a potential application in nano-electronic devices which have to work under harsh environment. In this study, one-dimensional nanowires(NWs) of cubic phase silicon carbide($\beta$-SiC) were efficiently produced by thermal chemical vapor deposition(T-CVD) synthesis of mixtures containing Si powders and hydrocarbon in a alumina boat about $T\;=\;1400^{\circ}C$ SEM images are shown that the temperature below $1300^{\circ}C$ is not enough to synthesis the SiC NWs due to insufficient thermal energy for melting of Si Powder and decomposition of methane gas. However, the SiC NWs are produced over $1300^{\circ}C$ and the most efficient temperature for growth of SiC NWs is about $1400^{\circ}C$ with an average diameter range between 50 ~ 150 nm. Raman spectra revealed the crystal form of the synthesized SiC NWs is a cubic phase. Two distinct peaks at 795 and $970\;cm^{-1}$ over $1400^{\circ}C$ represent the TO and LO mode of the bulk $\beta$-SiC, respectively. In XRD spectra, this result was also verified with the strongest (111) peaks at $2{\theta}=35.7^{\circ}$, which is very close to (111) plane peak position of 3C-SiC over $1400 ^{\circ}C$ TEM images are represented to two typical $\beta$-SiC NWs structures. One is shown the defect-free $\beta$-SiC nanowire with a (111) interplane distance with 0.25 nm, and the other is the stacking-faulted $\beta$-SiC nanowire. Two SiC nanowires are covered with $SiO_2$ layer with a thickness of less 2 nm. Moreover, by changing the flow rate of methane gas, the 300 sccm is the optimal condition for synthesis of a large amount of $\beta$-SiC NWs.

• Journal of the Korean Society for Marine Environment & Energy
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• v.11 no.2
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• pp.70-77
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• 2008

In this study, to establish countermeasure from marine casualties as a basic study fur long-term prediction of topographical change around Jinudo in the Nakdong river estuary, spatio-temporal topographical change monitoring was carried out. Also, in order to estimate the deposition variations concerning SS (Suspended Solid) flux which moved at St.S1 during neap and spring tide, respectively. From the topographical monitoring, it was found that the annual mean ground level and deposition rate were 141 mm and 0.36 mm/day and all parts except the northern part of Jinudo had the active topographical changes and a tendency to annually deposit. From vertical distribution of SS net fluxes, $SS_{LH}$ (latitudinal SS net flux) during spring tide overall flows average 28 $kg/m^2/hr$ (eastward), and $SS_{LV}$ (longitudinal SS net flux) flows average 11.1 $kg/m^2/hr$ (northward). And, $SS_{LH}$ overall flows average 4.8 $kg/m^2/hr$ (eastward), and $SS_{LV}$ flows average 1.5 $kg/m^2/hr$ (northward) during neap tide similar with spring tide. The depth averaged values of the latitudinal and longitudinal SS net fluxes during spring tide were approximately 6 times higher than those during neap tide. As result of, it was considered that topographical change of southern part of Jinudo was affected by resuspension of bottom sediments due to strong current in bottom layer during flood flow.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.151-151
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• 2009

Recently, there has been increasing interest in amorphous oxide semiconductors to find alternative materials for an amorphous silicon or organic semiconductor layer as a channel in thin film transistors(TFTs) for transparent electronic devices owing to their high mobility and low photo-sensitivity. The fabriction of amorphous oxide-based TFTs at room temperature on plastic substrates is a key technology to realize transparent flexible electronics. Amorphous oxides allows for controllable conductivity, which permits it to be used both as a transparent semiconductor or conductor, and so to be used both as active and source/drain layers in TFTs. One of the materials that is being responsible for this revolution in the electronics is indium-zinc-tin oxide(IZTO). Since this is relatively new material, it is important to study the properties of room-temperature deposited IZTO thin films and exploration in a possible integration of the material in flexible TFT devices. In this research, we deposited IZTO thin films on polyethylene naphthalate substrate at room temperature by using magnetron sputtering system and investigated their properties. Furthermore, we revealed the fabrication and characteristics of top-gate-type transparent TFTs with IZTO layers, seen in Fig. 1. The experimental results show that by varying the oxygen flow rate during deposition, it can be prepared the IZTO thin films of two-types; One a conductive film that exhibits a resistivity of $2\times10^{-4}$ ohm${\cdot}$cm; the other, semiconductor film with a resistivity of 9 ohm${\cdot}$cm. The TFT devices with IZTO layers are optically transparent in visible region and operate in enhancement mode. The threshold voltage, field effect mobility, on-off current ratio, and sub-threshold slope of the TFT are -0.5 V, $7.2\;cm^2/Vs$, $\sim10^7$ and 0.2 V/decade, respectively. These results will contribute to applications of select TFT to transparent flexible electronics.

• Korean Journal of Materials Research
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• v.9 no.1
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• pp.14-17
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• 1999

Tin oxide films as an anode layer for microbatteries were deposited by using rf magnetron sputtering. Characterization of the films was carried out in terms of working pressure in the range of 5~30 mtorr. Rf power and substrate temperature during deposition were fixed at 2.5W/$\textrm{cm}^2$ and A.T., respectively. The crystal orientation of $SnO_2$films was changed from (110) to (101) or (211) with the increasing working pressure. Refractive index and film density of the films also decreased with the increasing working pressure. The $SnO_2$ thin film formed under optimum conditions was found to have a reversible capacity of 446.9$\mu$Ah/$\textrm{cm}^2$-$\mu\textrm{m}$ and good reversibility when the working pressure was fixed at 10mtorr. As the working pressure decreased, film density increased. It was thought that the capacity of $SnO_2$films increased due to the increase in the amount of active materials which can react with Li electrochemically. Furthermore, cycle characteristics of the anode material was also influenced by film stress.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.5 no.4
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• pp.295-304
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• 2000

Vertical measurement of CTDT at about 30 min intervals and spatial surface temperature, salinity, and concentration of suspended particulate matters were conducted to elucidate the character of water column and the dispersal pattern in a floating ice-dominated fjord, Marian Cove, West Antarctica. Marian Cove showed two distinct water layers in terms of turbidity; 1) cold, fresh, and turbid surface plume in the upper 2 m,2) warm, saline, and relatively clean Maxwell Bay inflow between 15-45 m in water depth. Thermal melting of Maxwell Bay inflow and tidewater glacier/floating ices developed the surface mixed layer and the activity of floating ices cause Maxwell Bay inflow to be unstable. Due to the unstable water column, the development of Maxwell Bay inflow and subsequent surface plume are not influenced by tidal frequency. Coastal current generated by strong northwesterly wind may extend warm, saline, and turbid surface plume into the central part of the cove along the northern coast via the western coast of Weaver Peninsula. Terrigenous sediments of meltwaters from the glaciated ice cliffs near the corner of tidewater glacier and some coasts enter into the cove and their dispersion depends upon the hydrographic regimes (tide, wind, wave etc.). At the period of spring tide, the strong wind stress with the northwesterly wind direction reserve suspended sediment-fed surface plume and so allow the possibility of deposition of terrigenous sediments within the basin of cove.