• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
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• pp.205-206
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• 2008

The transparent conductive film was prepared by bar coating method of poly (3, 4-ethylenedioxythiophene) (PEDOT) and poly (sodium 4-stylenesulfonate) grafted multi-walled carbon nanotubes (MWNT-PSS) nanocomposites solution on the polyethylene terephthalate (PET) film. In this case, multi-wall carbon nanotubes was treated by chemical methods to obtain water soluble MWNT-PSS and then blending with PEDOT. The non-covalent bonding of polymer to the MWNT surface was confirmed by Fourier transform infrared (FT-IR), thermal gravimetric analysis (TGA) and Transmission electro microscope (TEM) investigation also showed a polymer-wrapped MWNT structure. Furthermore, the electrical, transmission properties of the transparent conductive film were investigated and compared with control samples are raw PEDOT films.

• 한국전기전자재료학회논문지
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• 제16권8호
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• pp.700-704
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• 2003

This paper describes on characteristics of 2" 3C-SiC wafer bonding using PECVD (plasma enhanced chemical vapor deposition) oxide and HF (hydrofluoride acid) for SiCOI (SiC-on-Insulator) structures and MEMS (micro-electro-mechanical system) applications. In this work, insulator layers were formed on a heteroepitaxial 3C-SiC film grown on a Si (001) wafer by thermal wet oxidation and PECVD process, successively. The pre-bonding of two polished PECVD oxide layers made the surface activation in HF and bonded under applied pressure. The bonding characteristics were evaluated by the effect of HF concentration used in the surface treatment on the roughness of the oxide and pre-bonding strength. Hydrophilic character of the oxidized 3C-SiC film surface was investigated by ATR-FTIR (attenuated total reflection Fourier transformed infrared spectroscopy). The root-mean-square suface roughness of the oxidized SiC layers was measured by AFM (atomic force microscope). The strength of the bond was measured by tensile strength meter. The bonded interface was also analyzed by IR camera and SEM (scanning electron microscope), and there are no bubbles or cavities in the bonding interface. The bonding strength initially increases with increasing HF concentration and reaches the maximum value at 2.0 ％ and then decreases. These results indicate that the 3C-SiC wafer direct bonding technique will offers significant advantages in the harsh MEMS applications.ions.

• Bulletin of the Korean Chemical Society
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• 제30권7호
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• pp.1573-1578
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• 2009

A computational study of the reactions between Zn-containing species, the products of the thermal decomposition of diethylzinc (DEZn) and water was investigated. The Zn-containing species – $C_2H_5)_2,\;HZnC_2H_5,\;and\;(ZnC_2H_5)_2$ – were assumed to react with water during ZnO metal organic chemical vapor deposition (MOCVD). Density functional theory (DFT) calculations at the level of B3LYP/6-311G(d) were employed for the geometry optimization and thermodynamic property evaluation. As a result dihydroxozinc, $Zn(OH)_2$, was the most probable reaction product common for all three Zn-containing species. A further clustering of $Zn(OH)_2$ was investigated to understand the initial stage of ZnO film deposition. In experiments, the reactions of DEZn and water were examined by in-situ Raman scattering in a specially designed MOCVD reactor. Although direct evidence of $Zn(OH)_2$ was not observed, some relevant reaction intermediates were successfully detected to support the validity of the gas phase reaction pathways proposed in the computational study.

• Smart Structures and Systems
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• 제6권7호
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• pp.793-810
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• 2010

This paper addresses the control issue of vibratory MEMS-based gyroscopes. This study considers a gyroscope that can be modeled by an inner mass attached to an outer mass by four springs and four dampers. The outer mass itself is attached to the rotating frame by an equal number of springs and dampers. In order to measure the angular rate of the rotating frame, a driving force is applied to the inner mass and the Coriolis force is sensed along the y-direction associated with the outer mass. Due to micro-fabrication imperfections, including anisoelasticity and damping effects, both gyroscopes do not allow accurate measurements, and therefore, it becomes necessary to devise feedback controllers to reduce the effects of such imperfections. Given an ideal gyroscope that meets certain performance specifications, a feedback control strategy is synthesized to reduce the error dynamics between the actual and ideal gyroscopes. For a dual-mass gyroscope, it is demonstrated that the error dynamics are remarkably decreased with the application of four actuators applied to both masses in the x and y directions. It is also shown that it is possible to reduce the error dynamics with only two actuators applied to the outer mass only. Simulation results are presented to prove the efficiency of the proposed control design.

• 한국세라믹학회지
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• 제37권8호
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• pp.731-738
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• 2000

KLN(K3Li2Nb5O15) has attracted a great deal of attention for their potential usefulness in piezoelectric, electro-optic, nonlinear optic, and pyroelectirc devices. Especially, the KLN single crystal has been studied in the field of optics and electronics. However it is hard to produce good quality single crystals due to the crack propagation during crystal growing. One of the solutions of this problem is prepartion of thin film. But the intensive study has not been conducted so far. In this study, after the KLN thin film were prepared by R.F. magnetron Sputtering method on SiO2/Si substrate, the post-annealing methods of RTA(rapid thermal annealin) and IPA(insitu post annealing) were employed. The deposition condition of KLN thin film was RF power(100 W), Working pressure(100 mtorr). The commonness of both RAT and IPA was that the higher were deposition and post annealing temperature, the higher was the intensity of XRD but the less surface roughness. The difference of post-annealing methods affected XRD phase and surface condition very much. And in IPA process, the influence of O2 had much effect on the formation of KLN phase.

• Environmental Engineering Research
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• 제10권1호
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• pp.38-44
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• 2005

Electro-thermal production of white phosphorus(WP, P4) generates substantial amount of highly toxic phossy water and sludges. Because of their high phosphorus contents and lack of reliable processing technology, large tonnages of these hazardous wastes have accumulated from current and past operations in the United States. In this study, two different methods for treatment of phosphorus sludge were investigated. These were bulk removal of WP by physical separation(froth flotation) and transformation of WP to oxyphosphorus compounds by air oxidation in the sludge medium. Kerosene, among other collectors, resulted in selective flotation of WP from the associated mineral gangue. Solvent action of kerosene occurring on the WP surface(by rendering WP particles hydrophobic) might produce the high selectivity of WP. The WP recovery in the froth was 79.3% from a sludge assaying 34.2% of WP. In the oxidation study, air gas was dispersed in the sludge medium by the rapid rotation of the impeller blades. The high level of sludge agitation intensity caused a fast completion of the oxidation reactions and it resulted in the high percentage conversion of WP to PO4-3 with PO3-3 making up almost all portion of oxyphosphorus compounds. The WP analysis on the treated sludge showed that supernatant solution and solid residue contained an average of 4.2 μg/L and 143 ppm respectively from the sludge containing about 26 g of WP. Further investigation will be required on operational factors to better understand the processes and achieve an optimum condition.

• Transactions on Electrical and Electronic Materials
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• 제17권4호
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• pp.189-195
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• 2016

Micro Hotplate (MHP) is the key component in micro-sensors, particularly gas sensors. Indeed, in metal oxide gas sensors MOX, micro-heater is used as a hotplate in order to control the temperature of the sensing layer which should be in the requisite temperature range over the heater area, so as to detect the resistive changes as a function of varying concentration of different gases. Hence, their design is a very important aspect. In this paper, we have presented the design and simulation results of a meander micro heater based on three different materials - platinum, titanium and tungsten. The dielectric membrane size is 1.4 mm × 1.6 mm with a thickness of 1.4 μm. Above the membrane, a meander heating film was deposed with a thickness of 100 nm. In order to optimize the geometry, a comparative study by simulating two different heater thicknesses, then two inter track widths has also been presented. Power consumption and temperature distribution were determined in the micro heater´s structure over a supply voltage of 5, 6, and 7 V.

• 한국전기전자재료학회논문지
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• 제24권10호
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• pp.803-806
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• 2011

1 mol% $Li_2O$ excess $0.9(Na_{0.52}K_{0.48})NbO_3-0.1LiTaO_3$ lead-free piezoelectric multilayer ceramic actuators were investigated to determine their aging properties. To reduce the thermal aging behavior, we applied a rectified unipolar electric field of 5 kV/mm to the specimen to accelerate the electric aging behavior. By employing a rectified unipolar electric field for the piezoelectric actuators, we could remove undesirable heating from the relaxation current in the motion of the ferroelectric domain. To accelerate the aging test, the applied electric fields had a frequency of 900 Hz. To have enough time for charging and discharging, we employed an accurate time constant to design the equivalent circuit model for the aging tester. To extract exact aging behavior, we measured the pseudo-piezoelectric coefficient before and after the aging process. We also measured the electro-mechanical coupling coefficient, the frequency-dependent dielectric permittivity, and the impedance to compare with fresh and aged specimen.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2008년도 춘계학술대회 논문집
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• pp.285-287
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• 2008

AAO(Anodic Aluminum Oxidation) method has been known that it is practically useful for the fabrication of nano-structures and makes it possible to fabricate the highly ordered nano masters on large surface and even on the 2.5 or 3D surface at low cost comparing to the expensive e-beam lithography or the conventional silicon processing. In this study, by using the multi-step anodizing and etching processes, highly ordered nano patterned master with concave shapes was fabricated. By varying the processing parameters, such as initial matter and chemical conditions; electrical and thermal conditions; time scheduling; and so on, the size and the pitch of the nano pattern can be controlled. Consequently, various alumina/aluminum nano structures can be easily available in any size and shape by optimized anodic oxidation in various aqueous acids. In order to replicate nano patterned master, the resulting good filled uniform nano molded structure through electro-forming process shows the validity of the fabricated nano pattern masters.

• Bulletin of the Korean Chemical Society
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• 제21권1호
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• pp.56-60
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• 2000

The mechanism of a matrix modification for the trace determination of volatile lead and bismuth by an electro-thermal atomic absorption spectrophotometry was studied by a X-ray diffractometry (XRD). For the investigation of structures, the ash products of the elements were produced by using a palladium as a matrix modifier with or without aluminum or nickel as an auxiliary modifier. The same charring conditions as in the analysis of samples were applied together with much concentrated solution of analytical elements and modifiers in a graphite furnace to get a large amount of the product for XRD. The XRD patterns showed PbPd3 for lead and BiPd3 for bismuth. These mean that the reaction procedures through the charring and atomization were changed from $Pb^{2+}$ ${\rightarrow}$ PbO ${\rightarrow}$$Pb^0$ to $Pb^{2+}$ ${\rightarrow}$ PbO ${\rightarrow}PbPd_3$ ${\rightarrow}$ Pb o for lead and from $Bi^{3+}$ ${\rightarrow}$ BiO ${\rightarrow}$ Bi o to $Bi^{3+}$ ${\rightarrow}$ BiO ${\rightarrow}$ $BiPd_3$ ${\rightarrow}$ $Bi^0$ for bismuth by the addition of modifiers. The volatile elements were stabilized by the formation of palladium alloys through a charring process. Charring temperatures were raised about 500 $^{\circ}C$ by the alloying and the atomization was also stabilized for the enhancement of sensitivities.