• 한국재료학회지
• /
• 제6권4호
• /
• pp.349-356
• /
• 1996

완화형 강유전체의 가장 대표적인 PMN계에서 첨가제의 종류와 함량, 측정온도, 인가 전계의형태 등의 변화에 따른 전계인가 변화특성을 광법위하게 조사하였다. Columbite precursor법에의해 분말을 준비하고 고상소결방법에 의하여 모든 시편을 제조하였다. 순수한 PMN에 첨가제로서 PbTiO3와 Pb(Zr, Ti)O3를 첨가한 경우에 완전한 perovskite 구조의 고용체가 형성되었음을 알 수 있었다. T$\varepsilon$max이상에서는 변위의 이력이 크게 발생하는 강유전체의 거동을 보여주었다. 양방향으로 전계를 인가하여 변위를 이용하면 발생 strain은 실온 근방에서 온도에 대하여 안정적이지만 단방향 전계에 따른 변위는 온도에 따라 크기가 변한다는 것을 알 수 있었고 유전상수가 큰 경우가 전왜의 크기 또한 큰 것을 알 수 있었다. 0.9MN-0.1PT와 0.8PMN-0.2PZT의 경우 최대가 되는 온도는 유전율이 최대가 되는 온도보다 더 낮은 온도에서 나타났다.

• 한국방사선학회논문지
• /
• 제1권3호
• /
• pp.17-21
• /
• 2007

We describe recent observations and measurements realized with microdot (MDOT) detectors having 50 mm, 100 mm, and 200 mm pitches for 3.7 keV X-rays. A gas gain of $3.1{\times}10^3$ has been measured with 50 mm pitch MDOT at potential difference much lower than those usually obtained with MSGCs. The defocusing effect caused by the existence of the readout lines passing below the insulator layer has been investigated from the drift voltage dependence of the count rate variation and the electric field simulation for all the detectors. Results concerning the spatial resolutions are presented with collimated X-ray beams.

• 한국마이크로전자및패키징학회:학술대회논문집
• /
• 한국마이크로전자및패키징학회 2000년도 Proceedings of 5th International Joint Symposium on Microeletronics and Packaging
• /
• pp.109-109
• /
• 2000

Recently, carbon nanotube has been investigating for field emission display ( (FED) applications due to its high electron emission at relatively low electric field. However, the growing of carbon nanotube generally requires relatively high temperature processing such as arc-discharge (5,000 ~ $20,000^{\circ}C$) and laser evaporation (4,000 ~ $5,000^{\circ}C$) methods. In this presentation, low temperature growing of carbon nanotube by plasma enhanced chemical vapor deposition (PECVD) using nickel catalyst which is compatible to conventional FED processing temperature will be described. Carbon n notubes with average length of 100 run and diameter of 2 ~ $3\mu$ill were successfully grown on silicon substrate with native oxide layer at $550^{\circ}C$using nickel catalyst. The morphology and microstructure of carbon nanotube was highly depended on the processing temperature and nickel layer thickness. No significant carbon nanotube growing was observed with samples deposited on silicon substrates without native oxide layer. This is believed due to the formation of nickel-silicide and this deteriorated the catalytic role of nickel. The formation of nickel-silicide was confirmed by x-ray analysis. The role of native oxide layer and processing parameter dependence on microstructure of low temperature grown carbon nanotube, characterized by SEM, TEM XRD and R없nan spectroscopy, will be presented.

• 전기화학회지
• /
• 제1권1호
• /
• pp.18-23
• /
• 1998

전기장이 충전층내 거대 이온성분자체의 분리를 위한 이론적 인 모델이 수행되었다 충전층내 여과재에서 전기적인 대류속도의 효과는 분자량이 큰 이온성 물질을 분리하기 위해서는 효과적이다. 이유는 전기장하에 거대이온성 분자체는 전기의 방향으로 빠르게 이온성분자체가 곧게 뻗는 현상때문이다. 이러한 분자체의 거동현상은 여과재내에 대류속도가 전기힘과 분자크기에 따라 대류속도가 다르기 나타나기 때문에 이들에 대한 연구는 충전층내에서 분자체를 분리하는데 도움이 된다 본 논문에서 여과재시스템내에서 이론분리는 확산에 대한 대류속도의 비$(Pe_t/Pe_g)$를 이용하여 예측하였으며 본 논문에서 얻어진 결과는 여과시스템을 설계하고 응용하는데 유효하게 적용될 것이며 이론적인 근거는 연산자 이론과 Reptation이론이 적용되였다.

• 한국자기공명학회논문지
• /
• 제16권2호
• /
• pp.111-121
• /
• 2012

The spin-lattice relaxation times, $T_1$, and spin-spin relaxation times, $T_2$, of the $^{27}Al$ and $^{87}Rb$ nuclei in $RbAl(CrO_4)_2{\cdot}2H_2O$ crystals were investigated. The presence of only one resonance line for the $^{27}Al$ nuclei indicates that the results in a dynamical averaging of the crystal electric field that produces a cubic symmetry field. The changes in the temperature dependence of $T_1$ are related to variations in the symmetry of the octahedra of water molecules surrounding $Al^+$ and $Rb^+$. The $T_1$ values for the $^{27}Al$ and $^{87}Rb$ nuclei are different due to differences in the local environments of these ions. We also compared these $^{27}Al$ and $^{87}Rb$ NMR results with those obtained for $RbAl(CrO_4)_2{\cdot}2H_2O$ crystals. The relaxation mechanisms of $RbAl(XO_4)_2{\cdot}nH_2O$ (X=Cr and S) crystals are characterized by completely different NMR behaviors.

• 유변학
• /
• 제10권4호
• /
• pp.195-201
• /
• 1998

반도성 고분자인 폴리아닐린과 폴리파라페닐렌을 이용한 전기유변유체의 유변학적 및 전기적 특성을 고찰하였다. 이들 반도성 고분자 현탁액은 분산입자와 현탁매질의 전기전도도 차이로 인하여 직류 전기장 하에서 큰 점도 증가를 보였다. 전기유변효과로 기인한 동적 항복응력은 낮은 전기장 하에서는 전기장 제곱에의 의존성을 보였으나 높은 전기장 하에서는 전기장의 1승에 비례하는 거동을 나타내었다. 항복 응력은 분산입자의 전기전도도가 증가함에 따라 최대값을 보이다가 다시 감소하는 현상을 나타내었다. 직류 전기장 하에서의 이러한 항복 응력 거동은 전도도 효과에 의한 맥스웰-와그너 계면편극화로 설명되는 현탁액의 유전 특성과 관련됨을 발견하였다. 계면 편극화 효과가 전기유변현상에 미치는 영향에 대한 더 깊은 이해와 분산액의 침강 안정성 개선을 위하여, 전기유변 효과의 조절이 가능할 뿐 아니라 현탁액의 콜로이드 안정성을 향상시킬 수 있는 여러 가지의 계면 활성제의 영향을 피력하였다.

• 천문학회지
• /
• 제36권spc1호
• /
• pp.93-99
• /
• 2003

Various attempts have been made to explain the: pronounced seasonal and universal time (UT) variations of geomagnetic indices. As one of such attempts, we analyze the hourly-averaged auroral electroject indices obtained during the past 20 years. The AU and AL indices maximize during summer and equinoctial months, respectively. By normalizing the contribution of the solar conductivity enhancement to the AU index, or to the eastward electrojet, it is found that the AU also follows the same semiannual variation pattern of the AL index, suggesting that the electric field is the main modulator of the semiannual magnetic variation. The fact that the variation pattern of the yearly-mean AU index follows the mirror image of the AL index provides another indication that the electric field is the main modulator of magnetic disturbance. The pronounced UT variations of the auroral electrojet indices are also noted. To determine the magnetic activity dependence, the probability of recording a given activity level of AU and AL during each UT is examined. The UT variation of the AL index, thus obtained, shows a maximum at around 1200-1800 UT and a minimum around 0000-0800 UT particularly during winter. It is closely associated with the rotation of the geomagnetic pole around the rotational axis, which results in the change of the solar-originated ionospheric conductivity distribution over the polar region. On the other hand the UT variation is prominent during disturbed periods, indicating that the latitudinal mismatch between the AE stations and the auroral electrojet belt is responsible for it. Although not as prominent as the AL index, the probability distribution of the AU also shows two UT peaks. We confirm that the Dst index shows more prominent seasonal variation than the AE indices. However, the UT variation of the Dst index is only noticeable during the main phase of a magnetic storm. It is a combined result of the uneven distribution of the Dst stations and frequent developments of the partial ring current and substorm wedge current preferentially during the main phase.

• 전자공학회논문지A
• /
• 제33A권10호
• /
• pp.123-129
• /
• 1996

LDD structure is widely accepted in fabricating short channel MOSFETs due to reduced short channel effect originated form lower drain edge electric field. However, modeling of the LDD device is troublesome because the analysis methods of LDD region known are either too complicated or inaccurate. To solve the problem, this paper presents a nonlinear resistance model for the LDD region based on teh fact that the electron mobility changes with positive gate bias because accumulation layer of electrons is formed at the surface of the LDD region. To prove the usefulness of the model, single source/drain and LDD nMOSFETs were fabricated with 0.35$\mu$m CMOS technolgoy. For the fabricated devices we have measured I$_{ds}$-V$_{gs}$ characteristics and compare them to the modeling resutls. First of all, we calculated channel and LDD region mobility from I$_{ds}$-V$_{gs}$ characteristics of 1050$\AA$ sidewall, 5$\mu$m channel length LDD NMOSFET. Then we MOSFET and found good agreement with experiments. Next, we use calculated channel and LDD region mobility to model I$_{ds}$-V$_{gs}$ characteristics of LDD mMOSFET with 1400 and 1750$\AA$ sidewall and 5$\mu$m channel length and obtained good agreement with experiment. The single source/drain device characteristic modeling results indicates that the cahnnel mobility obtained form our model in LDD device is accurate. In the meantime, we found that the LDD region mobility is governed by phonon and surface roughness scattering from electric field dependence of the mobility. The proposed model is useful in device and circuit simulation because it can model LDD device successfully even though it is mathematically simple.

• 한국세라믹학회지
• /
• 제52권1호
• /
• pp.77-82
• /
• 2015

The effect of the electrode type on the dielectric and piezoelectric properties of $Pb(Mg_{1/3}Nb_{2/3})O_3-PbZrO_3-PbTiO_3$ (PMN-PZT) single crystals was investigated in an effort to improve their properties for various piezoelectric applications. First, three different types of PMN-PZT single crystals [PMN-PZT-A (piezoelectrically soft type; dielectric constant ~ 10,000), PMN-PZT-B (piezoelectrically soft type; phase-transition temperature between the rhombohedral and tetragonal phases ($T_{RT}$) ~ $145^{\circ}C$), PMN-PZT-C (piezoelectrically hard type; high mechanical quality factor ($Q_m$) ~ 1,000)] were fabricated using the solid-state single crystal growth (SSCG) method. Then, four different types of electrodes [sputtered Au, sputtered Cr/Au, sputtered Ti/Au, and fired Ag] were formed on the single crystals, and their dielectric and piezoelectric properties were measured. The single crystals with a sputtered Ti/Au electrode showed the highest dielectric and piezoelectric constants but the lowest coercive electric field ($E_C$). The single crystals with a fired Ag electrode showed the lowest dielectric and piezoelectric constants but the highest coercive electric field ($E_C$). This dependence on the type of electrode was most significant in the piezoelectrically hard PMN-PZT-C single crystals. However, the effects of the electrode type on the phase transition temperatures ($T_C$, $T_{RT}$) and dielectric loss were negligible. These results clearly demonstrate that it is important to select an appropriate electrode so as to maximize the dielectric and piezoelectric properties of single crystals in each type of piezoelectric application.

• Transactions on Electrical and Electronic Materials
• /
• 제4권6호
• /
• pp.9-12
• /
• 2003

The electrical properties of stabilized amorphous selenium typical of the material used in direct conversion x-ray imaging devices are reported. Carrier mobility was measured using time-of-flight (TOF) measurements to investigate the transport properties of holes and electrons in stabilized a-Se film. A laser beam with pulse duration of 5 ns and wavelength of 350nm was illuminated on the surface of a-Se with thickness of 400 $\mu\textrm{m}$. The photo induced signals of a-Se film as a function of time were measured. The measured transit times of hole and electron were about 8.73${\mu}\textrm{s}$ and 229.17${\mu}\textrm{s}$, respectively. The hole and electron drift mobilities decreases with increase of electric field up to 4V/$\mu\textrm{m}$. Above 4V/$\mu\textrm{m}$, the measured drift mobilities exhibited no observable dependence with respect to electric field. The experimental results showed that the hole and electron drifting mobility were 0.04584 $\textrm{cm}^2$ V$\^$-1/s$\^$-1/ sand 0.00174 $\textrm{cm}^2$V$\^$-1/s$\^$-1/ at 10 V/$\mu\textrm{m}$.