• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2006년 제4회 한국유체공학학술대회 논문집
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• pp.497-500
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• 2006

An theoretical analysis on the electro-osmotic flow in a 2-dimensional slit, that is induced by an external electric field acting on the electrical double layers near the slit wall, was performed. Especially, although there were many studies on the interacting electrical double layers, it was found in this study that they have several physical or mathematical fallacies. To resolve these, the general solution on the charge-regulating slit with the height as a parameter was obtained. The results of this work can provide the electrokinetic solution of nanoscale slit with the electrical double layer interaction as well as that of microscale slit without the interaction and can be used as the benchmark of a numerical analysis and the reference of electrokinetic flow path design.

• Bulletin of the Korean Chemical Society
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• 제35권1호
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• pp.135-140
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• 2014

A bent-shape triazolyl derivative was synthesized via click chemistry, and its photophysical property was investigated in various solvents. In contrast to the invisible ultraviolet emission of other solutions, the chloroform solution exhibited a blue light emission at 460 nm. Furthermore, the blue fluorescence intensified as the UV exposure time at 365 nm increased. On the basis of $^1H$-NMR, pH paper, and acid-addition studies, we confirmed that chloroform was decomposed into HCl with the aid of the triazolyl derivative. The density functional theory calculations suggested that the eye-detectable blue fluorescence was attributed to an intramolecular charge transfer process of the protonated triazolyl derivative in the chloroform solution.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.3108-3113
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• 2008

This paper investigated the behaviors of combustion characteristics at part load condition with various intake charge motions induced by the port masking schemes in the CVVT (Continuously Variable valve Timing) engine. Time resolved in-cylinder and exhaust emissions were measured by the fast response HC and NOx analyzers to examine their formation mechanisms and behavior characteristics. As a result, in-cylinder HC decreased with the advanced intake valve timings but HC at the exhaust port increased due to the worse combustion stabilities. However HC reduction could be achieved by the application of the port maskings with a enhancement of the engine stability. NOx also decreased with early intake timings by internal EGR but increased with the charge motion controls which enhance the combustion behavior.

• JSTS:Journal of Semiconductor Technology and Science
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• 제10권2호
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• pp.79-99
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• 2010

Pulsed current-voltage (I-V) methods are introduced to evaluate the impact of fast transient charge trapping on the performance of high-k dielectric transistors. Several pulsed I-V measurement configurations and measurement requirements are critically reviewed. Properly configured pulsed I-V measurements are shown to be capable of extracting such device characteristics as trap-free mobility, trap-induced threshold voltage shift (${\Delta}V_t$), as well as effective fast transient trap density. The results demonstrate that the pulsed I-V measurements are an essential technique for evaluating high-$\kappa$ gate dielectric devices.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.2020-2021
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• 2007

Viologen derivative has been widely investigated because of their well-electrochemical behavior including the electron acceptor for the electric charge delivery mediation of the devices. The viologen exist in three main oxidation states, namely, $V^{2+}{\rightleftarrows}V^{{\cdot}+}{\rightleftarrows}V^0$. These redox reactions are highly reversible and can be cycled many times without significant side reaction. In this paper, we determined the time dependence to resonant frequency shift of QCM during self-assembly process and the electrochemical behavior of the self-assembled viologen monolayers by electrochemical QCM method. The redox reactions of viologen were highly reversible and the EQCM has been employed to monitor the electrochemically induced adsorption of SAMs during the redox reactions.

• 한국응용과학기술학회지
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• 제25권2호
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• pp.205-210
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• 2008

The transformation of the liquid crystal complex made by binding of anionic surfactant, sodium dodecyl sulfate (SDS), into high charge density cationic polymer, the homopolymer of diallyldimethylammonium chloride (PDADMAC) was induced by adding of nonionic surfactants and investigated by means of microscopy and FE.SEM. Among nonionic surfactants in this experiments polyethylene glycol (3 mol) ether of lauryl alcohol (laureth-3) made variation in the complex. The laureth-3 transformed the complex into spherulite vesicle with the size of ca.$100{\mu}m$. This change increased the viscosity and the turbidity of the solution phase separated originally. Microscope showed that they are spherulite particles and polarized microscope suggested they are multi.lamellar liquid crystals. FE-SEM also proved that explicitly.

• Bulletin of the Korean Chemical Society
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• 제14권6호
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• pp.704-708
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• 1993

The intramolecular charge transfer (ICT) phenomena of the photoexcited 2-biphenylcarboxylic acid (2BPCA) and 4-biphenylcarboxylic acid (4BPCA) have been investigated in some surfactant micellar solutions. The ICT emission of 4BPCA and 2BPCA in aqueous solution at sufficiently low pH (1-3) has been observed to be markedly quenched and blue-shifted upon addition of a cationic surfactant, cetyltrimethylammonium chloride (CTAC) in contrast to little change in anionic sodium dodecyl sulfate (SDS) and neutral Brij 35. An anionic emission band has been observed to be enhanced at expense of the ICT emission as a function of the concentration of CTAC. These results with the micellar effects on the fluorescence decay kinetics of 4BPCA suggest that formation of the ICT state of the excited acids is inhibited by CTAC-induced proton transfer as well as the decrease in the polarity and/or hydrogen-bonding ability of the micellar microenvironment entrapping the acids.

• 센서학회지
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• 제2권1호
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• pp.65-74
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• 1993

본(本) 연구(硏究)에서는 소형(小型) 정전유도형(靜電誘導型) 모터를 제작하고 이 모터에 인가하는 3상(相) 교류전압(交流電壓) 및 주파수(周波數)를 가변(可變)하였을 때의 회전자(回轉字)의 회전속도(回轉速度)의 특성을 실험적으로 검토하였다. 또한 정전유도형(靜電誘導型) 모터의 작동기구상(作動機構上) 회전자(回轉字) 표층물질(表層物質) 및 내층물질(內層物質)의 표면저항율(表面抵抗率), 비유전율(比誘電率) 및 전하완화시정수(電荷緩和時定數)를 변화시켜 회전자(回轉字) 및 고정자(固定子) 사이의 전계강도(電界强度) 및 회전자(回轉字) 표면물질상(表面物質上)의 표면유기전하(表面誘起電荷)의 분포(分布) 및 유기속도(誘起速度)를 변화시킴으로서 소형(小型) 정전유도형(靜電誘導型) 모터의 회전자의 회전속도에 미치는 영향을 검토하였다. 실험(實驗) 결과(結果), 회전자(回轉字) 표층물질(表層物質)의 비유전율(比誘電率), 표면저항률(表面抵抗率) 및 전하완화시정수(電荷緩和時定數) 및 내층물질(內層物質)의 비저항율(比抵抗率)이 모터의 회전속도(回轉速度)에 매우 큰 영향을 미침이 확인되었다. 또한 모터에 인가하는 3상(相) 전원(電源)의 전압(電壓) 및 주파수(周波數)도 모터의 회전(回轉)에 매우 큰 영향을 주며, 회전속도(回轉速度)는 인가전압(印加電壓) 및 주파수(周波數)에 일차(一次) 비례(比例)하여 증가함을 보여주었다. 회전자의 표층물질(表層物質)이 $BaTiO_{3}$ 80% 내층물질(內層物質)이 Cu 일때 무부하(無負荷) 최대속도(最大速度)는 4.5 kV, 220 Hz에서 5500 rpm이 얻어졌다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
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• pp.99-99
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• 2013

In this talk, I will present two research works in progress, which are: i) mapping of piezoelectric polarization and associated charge density distribution in the heteroepitaxial InGaN/GaN multi-quantum well (MQW) structure of a light emitting diode (LED) by using inline electron holography and ii) in-situ observation of the polarization switching process of an ferroelectric Pb(Zr1-x,Tix)O3 (PZT) thin film capacitor under an applied electric field in transmission electron microscope (TEM). In the first part, I will show that strain as well as total charge density distributions can be mapped quantitatively across all the functional layers constituting a LED, including n-type GaN, InGaN/GaN MQWs, and p-type GaN with sub-nm spatial resolution (~0.8 nm) by using inline electron holography. The experimentally obtained strain maps were verified by comparison with finite element method simulations and confirmed that not only InGaN QWs (2.5 nm in thickness) but also GaN QBs (10 nm in thickness) in the MQW structure are strained complementary to accommodate the lattice misfit strain. Because of this complementary strain of GaN QBs, the strain gradient and also (piezoelectric) polarization gradient across the MQW changes more steeply than expected, resulting in more polarization charge density at the MQW interfaces than the typically expected value from the spontaneous polarization mismatch alone. By quantitative and comparative analysis of the total charge density map with the polarization charge map, we can clarify what extent of the polarization charges are compensated by the electrons supplied from the n-doped GaN QBs. Comparison with the simulated energy band diagrams with various screening parameters show that only 60% of the net polarization charges are compensated by the electrons from the GaN QBs, which results in the internal field of ~2.0 MV cm-1 across each pair of GaN/InGaN of the MQW structure. In the second part of my talk, I will present in-situ observations of the polarization switching process of a planar Ni/PZT/SrRuO3 capacitor using TEM. We observed the preferential, but asymmetric, nucleation and forward growth of switched c-domains at the PZT/electrode interfaces arising from the built-in electric field beneath each interface. The subsequent sideways growth was inhibited by the depolarization field due to the imperfect charge compensation at the counter electrode and preexisting a-domain walls, leading to asymmetric switching. It was found that the preexisting a-domains split into fine a- and c-domains constituting a $90^{\circ}$ stripe domain pattern during the $180^{\circ}$ polarization switching process, revealing that these domains also actively participated in the out-of-plane polarization switching. The real-time observations uncovered the origin of the switching asymmetry and further clarified the importance of charged domain walls and the interfaces with electrodes in the ferroelectric switching processes.

• JSTS:Journal of Semiconductor Technology and Science
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• 제12권3호
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• pp.360-369
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• 2012

The causes of showing different subthreshold slopes (SS) in programmed and erased states for two different charge trap flash (CTF) memory devices, SONOS type flash memory with gate-all-around (GAA) structure and TANOS type NAND flash memory with planar structure were investigated. To analyze the difference in SSs, TCAD simulation and low-frequency noise (LFN) measurement were fulfilled. The device simulation was performed to compare SSs considering the gate electric field effect to the channel and to check the localized trapped charge distribution effect in nitride layer while the comparison of noise power spectrum was carried out to inspect the generation of interface traps ($N_{IT}$). When each cell in the measured two memory devices is erased, the normalized LFN power is increased by one order of magnitude, which is attributed to the generation of $N_{IT}$ originated by the movement of hydrogen species ($h^*$) from the interface. As a result, the SS is degraded for the GAA SONOS memory device when erased where the $N_{IT}$ generation is a prominent factor. However, the TANOS memory cell is relatively immune to the SS degradation effect induced by the generated $N_{IT}$.