Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference (한국전기전자재료학회:학술대회논문집)
The Korean Institute of Electrical and Electronic Material Engineers
- Annual
1998.11a
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In this paper, we have studied a variation of I-V characteristics, and time-dependent dielectric breakdown(TDDB) of thin layer NO and ONO film depending on nitridation and reoxidation time, respectively, and measured a variation of leakage current and charge-to-breakdown(Q
$\_$ bd/) of optimized NO and ONO film depending on ambient temperature, and then compared with the properties of conventional SiO$_2$ . From the results, we find that these NO and ONO thin films are strongly influenced by process time and the optimized ONO film shows superior dielectric characteristics, and Q$\_$ bd/ performance over the NO film and SiO$_2$ , while maintaining a similar electric field dependence compared with NO layer. -
기존의 바이폴라 논리회로에서 신호변환시 베이스 영역의 소수 캐리어를 빨리 제거 하기 위해서, 베이스 부분의 매몰충을 줄여서 npn트랜지스터의 베이스와 에피충과 기판사이에 병합 pnp 트랜지스터를 생성한 트랜지스터와 게이트 당 전달 지연 시간을 측정하기 위한 링-발진기를 설계, 제작하였다. 게이트의 구조는 수직 npn 트랜지스터와 기판과 병합 pnp 트랜지스터이다. 소자 시뮬레이션의 자료를 얻기 위하여 수직 npn 트랜지스터와 병합 pnp 트랜지스터의 전류-전압 특성을 분석하여 특성 파라미터를 추출하였다. 결과로서 npn 트랜지스터의 에미터의 면적이 기존의 접합넓이에 비해서 상당히 적기 때문에 에미터에서 진성베이스로 유입되는 캐리어와 가장자리 부분으로 유입되는 캐리어가 상대적으로 많기 때문에 이 많은 양은 결국 베이스의 전류가 많이 형성되며, 또 콜렉터의 매몰층이 거의 반으로 줄었기 때문에 콜렉터 전류가 적게 형성되어 이득이 낮아진다. 병합 pnp 트랜지스터는 베이스폭이 크고 농도 분포에서 에미터의 농도와 베이스의 농도 차이가 적기 때문에 전류 이득이 낮아졌다. 게이트를 연결하여 링-발진기를 제작하여 측정한 AC특성의 출력은 정현파로 논리전압의 진폭은 200mV, 최소 전달 지연시간은 211nS이며, 게이트당 최소 전달지연 시간은 7.26nS의 개선된 속도 특성을 얻었다.
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Film characteristics of thin reoxidized nitrided oxides were investigated by SIMS analysis and C-V method in order to use the gate dielectric for charge-trap type NVSMs instead of ONO stacked layers. Nitric oxide(NO) annealed film has the nitrogen content sharply peaked at the Si-SiO
$_2$ interface, while it is broad for nitrous oxide($N_2$ O) ambient. The nitrogen peak concentration increased with anneal temperature and time. The position of nitrogen content in the oxide layer was due to be precisely controlled. For the films annealed NO ambient at 80$0^{\circ}C$ for 30min. followed by reoxidized at 85$0^{\circ}C$ , the maximum memory window of 3.5V was obtained and the program condition was +12V, 1msec for write and -l3V, 1msec for erase. -
An anomalous current characteristics which show the superposition of a low current level and high current level at the subthreshold region when SONOSFETs are in memory states were investigated. We have assumed this phenomena were resulted from the effect of parasitic transistors by LOCOS isolation and were modeled to a parallel equivalent circuit of one memory transistor and two parasitic transistors. Theoretical curves are well fitted in measured log I
$_{D}$ -V$_{G}$ curves independent of channel width of memory devices. The difference between low current level and high current level is apparently decreased with decrease of channel width of devices because parasitic devices dominantly contribute to the current conduction with decrease of channel width of memory devices. As a result, we concluded that the LOCOS isolation has to selectively adopt in the design of process for charge-trap type NVSM.VSM. -
Thermal behavior of Flow Pattern Defect (FPD) and Large Pit (LP) in Czochralski Silicon crystals was investigated by applying high temperature (
$\geq$ 1100$^{\circ}C$ ) annealing and non-agitation Secco etching. For evaluation of the effect of LP upon device performance / yield, DRAM and ASIC devices were fabricated. The results indicate that high temperature annealing generates LPs whereas it decreases FPD density drastically, and LP does not have detrimental effects on the performance / -
The properties of ZrN layer deposited by Sputtering system have been investigated in the application of diffusion barrier layer to copper. ZrN layer exhibited a excellent barrier property up to
$700^{\circ}$ and higher resistivity. If an excess$O_2$ is protected during the process of ZrN deposition, ZrN layer will be possible to use a diffusion barrier layer to copper. -
Lithiated cobalt and nickel oxides are becoming very attractive as active cathode materials for secondary lithium ion secondary battery.
$LiCoO_2$ is easily synthesized from lithium cobalt salts, but has a relatively high oxidizing potential on charge. LiNiOz is synthesized by a more complex procedure and its nonstoichiometry significantly degraded the charge-discharge characteristics. But$LiNiO_2$ has a lower charge potential which increases the system stability. Lithiated cobalt and nickel oxides are iso-structure which make the preparation of solid solutions of$LiNi_{1-x}Co_xO_2$ for O$LiCoO_2 and LiNiO_2$ electrode. The aim of the presentb paper is to study the electrochemical behaviour, as weU as the possibilities for practical application of layered Iithiated nickel oxide stabilized by $Co^{3+}$ substitution as active cathode materials in lithium ion secondary battery. -
A new treatment of LiV
$_3$ O$_{8}$ has beer proposed for improving its electrochemical behavior as a cathode material secondary lithium batteries. Early in its development, the preparation method of LiV$_3$ O$_{8}$ strongly influenced its electrochemical properties, such as discharge capacity, rate capability and cycling efficiency. In the present experiment, a new synthesis route has been applied to obtain LiV$_3$ O$_{8}$ . Instead of the conventional high temperature technique leading to the crystalline form, a solution technique producing the amorphous form has been used. This material, after dehydration, shows an electrochemical performance exceeding that of the crystalline one. These measurements showed that the ultrasonic treatment process of crystalline LiV$_3$ O$_{8}$ causes a decrease in crystallinity and considerable increases in specific surface area and interlayer spacing. So the ultrasonic method provides a convenient means for improving the electrochemical behavior of LiV$_3$ O$_{8}$ as a cathode material for secondary lithium batteries.batteries. -
BST(66/34) and BSCT(60/30/10) ceramics were prepared by mixed oxide method and studied about the microstructural and dielectric properties with
$Y_2$ O$_3$ , Dy$_2$ O$_3$ , La$_2$ O$_3$ , MnCO$_3$ . The grain size of undoped BST was 20~30${\mu}{\textrm}{m}$ , but that of BST, doped content of MnCO$_3$ was 0.1 mol%, was decreased with increasing the contents of$Y_2$ O$_3$ . As the content of$Y_2$ O$_3$ was Increased, Tc was shifted to lower temperature and dielectric constant at Tc was decreased. The dielectric constant of doped BSCT(60/30/10) ceramics ( 0.9 mol%$Y_2$ O$_3$ . and 0.1 mol% MnCO$_3$ ) was about 8, 000 at Tc( 22$^{\circ}C$ ). -
(Ba.Sr)TiO
$_3$ (BST) ceramics were fabricated with different Ba/Sr ratios and the str dielectric properties of the BST bulk ceramics were investigated. As the Ba/sr ratios dielectric constant decreased. (Ba$_{0.7}$ Sr$_{0.3}$ )TiO$_3$ (BST(70/30)) showed a maximum dielec value of$\varepsilon$ $_{r}$ =8.856, this showed that the decrease of Ba/Sr ratios had made BST thin dielectrics. Targets were fabricated and made into film by PLD process and the thin film by PLD process have good stoichiometry with the targets.rgets. -
(1-X)LTC-XHTC composites were manufactured with the variation of X in the range of 0.3
$\leq$ X$\leq$ 0.6 and its dielectric properties were investigated. Here, LTC and HTC are PZN-BT-PT -based ceramics with quire temperature(Tc) of 100。 C-3$0^{\circ}C$ , respectively. 0.6HTC-0.4LTC composite ceramics show excellent values of$\Delta$ $\varepsilon$ $_{r}$ /$\varepsilon$ [%] which were -7.1% at -2$0^{\circ}C$ and -12% at 5$0^{\circ}C$ , respectively. It is thought that composite ceramics with above results can be applied to electrostrictive actuator, high voltage ceramic capacitor etc.mic capacitor etc.r etc.c. -
Structural and Electrical Properties of (x)Ba
$TiO_3$ -(1-x)Sr$TiO_3$ Ceramics with Contents Sr$TiO_3$ A BaTiO$_3$ was annexed to SrTiO$_3$ , (x)BaTiO$_3$ -(1-x)SrTiO$_3$ (0.7$\leq$ X$\leq$ 1) ceramics with stable dielectric and electrical properties in high voltage were manufactured. Structural, dielectric and electrical properties were surveyed with the contents of SrTiO$_3$ . The open porosity and sintering density were excellent in 0.9BaTiO$_3$ -0.1SrTiO$_3$ , the grain size of 0.9BaTiO$_3$ -0.1SrTiO$_3$ was maximum at 12.40[${\mu}{\textrm}{m}$ ]. Increasing SrTiO$_3$ mol ratio, the curie temperature was shifted low temperature and the supreme permittivity was increased. In line with increasing of supplied voltage, permitivity was decreased slightly. -
In this paper, to implement the electrical equivalent modeling of powder electroluminescent device, capacitate equation of device was chosen. The conventional structure device which have dielectric and phosphor layer between electrodes, and the single emission structure device which means that dielectric and phosphor were mixed between electrodes, were investigated. As a result, it was possible to make the equation that is transferred capacitance to phosphor layer, and using measured brightness efficiency and conductivity of devices was calculated.
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Electroluminescent(EL) devices based on organic materials have been of great interest due to their possible applications for large-area flat-panel displays, where they are attractive because of their capability of multicolor emission, and low operation voltage. In this study, glass substrate/ITO/Eu(TTA)
$_3$ (Phen)/Al(A), glass substrate/ITO/TPD/Eu(TTA)$_3$ (p-hen)/Al(B) and glass substrate/ITO/TPD/Eu(TTA)$_3$ (phen)/AlQ$_3$ /Al(C) structures were fabricated by vacuum evaporation method. where aromatic diamine(TPD) was used as a hole transporting material, Eu(TTA)$_3$ (phen) as an emitting material. and tris(8-hydroxyquinoline)Aluminum(AlQ$_3$ ) as an electron transporting layer. Electroluminescent(EL) and I-V characteristics of Eu(TTA)$_3$ (Phen) with a various thickness were investigated. This structure shows the red EL spectrum, which is almost the same as the PL spectrum of Eu(TTA)$_3$ (phen). I-V characteristics of this structure show that turn-on voltage was 9V and current density was 0.01A/$\textrm{cm}^2$ at a dc operation voltage of 9V. Electrical transporting phenomena of these structures was explained using the trapped- charge-limited current model with I-V characteristics. -
Poly(3-hexylthiophene)(P3HT) was synthesized by use of FeCl
$_3$ as a oxidizing agent at$25^{\circ}C$ . The infrared spectrum of our polymer gave good evidence for the conjugation of 3-hexylthiophene monomer unit. P3HT contains the HT(head-to-tail) linkage larger than 64% based on NMR analysis. Electronic absorption and photoluminescence studies show that cast films of P3HT have three exciting state. Absorption spectrum was separated with three maximum peaks by Giese-French method and shifted to the shorter wavelength with increasing temperature. Separated absorption spectrum of P3HT is well adapted to PL peak appeared at longer wavelength. Low temperature PL spectrum is well separated at 669nm, 733nm and 812nm. -
We have investigated the effects of ultraviolet (UV) light irradiation condition and imidization temperature for the generation of pretilt angle in nematic liquid crystal (NLC) on the two kinds of the polyimide (PI) surfaces. High pretilt angle of NLC is generated with oblique p-polarized UV light irradiation of 30
$^{\circ}$ on PI surface for 20 min. Also, the high pretilt angle of NLC is generated with oblique p-polarized UV light irradiation of 10-30$^{\circ}$ on PI surface at 20min. The pretilt angle of NLC decreases with increasing the imidization temperature on all rubbed PI surfaces ; the pretilt angle of NLC with oblique p-polarized UV light irradiation of 30$^{\circ}$ on PI surface decreases with increasing the imidization temperature. The high pretilt angle of NLC is observed due to high photo-depolymerization reaction by low surface energy at low imidization temperature. We suggest that the pretilt angle of NLC is strongly attributed to the photo-depolymerization reaction with the UV light irradiation condition and imidization temperature. -
The mechanism of response time and viewing angle in in-plane switching ( IPS ) liquid crystal display ( LCD ) were investigated. The response time of photo-aligned IPS-LCD is fast compared with rubbing-aligned IPS-LCD on polyimide ( PI ) surface. The decay time
$\tau$ $\_$ d/ is decreased with increasing the azimuthal anchoring energy A$\psi$ due to the steric interaction between the LC molecules and side chain of polymer. The viewing angle of IPS-LCD is increased by using photo-depolymerizatin method ; about${\pm}$ 70$^{\circ}$ at all direction. -
A study to identify the energized status of the 22.9kV underground power cable by the detection of vibration was reformed. We derived that there exists vibration at double the line frequency in live cables by electromagnetic force. The vibration can be picked up by accelerometer sensor. A prototype was tested on the underground distribution system in Chonan Station, KEPCO. The results are presented and suggest the applicability of the detecting device.
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We give pressure stimulation into organic thin films and detect the induced displacement current. then manufacture a device under the accumulation condition that the state surface pressure is 15[mN/m]. In processing of a device manufacture. We can see the process is good from the change of a surface pressure for organic thin films and transfer ratio of area per molecule. The structure of manufactured device is Au/organic thin films(polyimide)/Au, the number of accumulated layers are 31,35, and 41. I-V characteristic of the device is measured from 0[V] to +5[V]. The maximum value of measured current is increased as the number of accumulated layers are decreased. The resistance for the number of accumulated layers, the energy density for an input voltage show desired results, and the insulation of a thin film is better as the interval between electrodes is larger.
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Recently, extending the local broadcasting and increasing lots of informations. The low-loss communication cable is required in proportion as frequency .The reason of transportation loss causes to using the high frequencies like hundreds of MHz or decades of GHz. For the low transportation loss. It is required the developing-technology of foaming and the high foamed insulator with the dielectric ratio of the nearest to 1. Therefor, there is the purpose of developing the insulating materials for the low dielectric ratio. Also it is important to measure the attenuation, which is one of the important parameters.sa the evaluation of transportation characteristic with frequency in the communication cable. In this paper,the result showed that the dielectric ratio(1.4) of the nearest to 1 and low attenuation with high frequency were very related to the transportation and reflection characteristics such as propagation velocity (82.27%). Delay time and voltage standing wave ratio(VSWR).
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New diagnostic techniques have been tried on the applications of chemical, physical and micro-structural methods because there was a limit to diagnose degradation in Korean Underground Residential Distribution (URD) power cables with the conventional electrical methods. In this study, non-electrical properties were carried out as such. Characterization of interface layer was analyzed by X-ray, characterization of insulator by water tree, degree of crosslinking, shrinkage as well as
${\mu}$ -FTIR, characterization of semiconductive layer by volume resistivity. Electrical properties were also performed by leakage current. -
Light-emitting diode(LEDs), diode arrays, and phosphor display panels are finding increased use in a variety of commercial applications. Present and anticipated application of these devices include solid state indicator(e.g., digital clocks, meter readout) and display systems(e.g., instrument panels, TV display), the application being determined by the light -output capability and size availability(cost) of the particular device. In this work, Phosphor based on ZnS:Cu are used. Relation by luminance with the thickness of insulating layer and phosphor layer are discussed. Increased thickness of insulating layer are stable on voltage to 300V. By considering thickness and voltage, optimal structure and thickness are investigated. Also in order to maximize even surface emission, various sieving process are introduced. Very similar phosphor particle size is selected. Luminance by various wave intensity is also investigated. 150cd/m
$^2$ luminance are investigated in stable voltage and frequency. -
Amorphous chalcogenide thin films, especially a-(Se, S) based films, exhibit a number of photoinduced phenomena not observed in other types of amorphous thin films. The polarization holographic grating has been formed in amorphous As-Ge-Se-S thin films using two linearly polarized He-Ne laser light. In addition, dffraction efficiency has been measured by the same laser of a relative lower intensity at the same time.
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The X-ray spectra dependence for intensifying screens of medical radiography was investigated through analysis of the absorbed coefficiency(
${\mu}$ ), absorbed efficiency(η$\sub$ ${\alpha}$ /) and absorbed ratio(R). It was found that the absorbed coefficiency was increased in the order of CaWO$_4$ $_4$ screen showed the highest value. -
We studied on the ultra thin L-
${\alpha}$ -DLPC by LB method. The$\pi$ -A isotherm of the L-${\alpha}$ -DLPC was measured at the air-water interface varying with the compressing speed and amounts of solutions for spreading. The molecular arrangement of deposited films were evaluated by measuring the absorption with the UVspectrometer. And we made structures of metal(Au)/L-${\alpha}$ -DLPC/Metal(Au) and examined electron through L-${\alpha}$ -DLPC LB films by means of current-voltage(I-V) measurement. -
A new planar-type micro gas sensor was designed and fabricated on silicon substrate and the operating characteristics of the sensor were investigated. The thin sensitive film of the sensor was fabricated by spin-coating of the SnO
$_2$ sol solution which was synthesized by hydrothermal method. The spin-coating method for preparation of sensing layer was adopted to improve the long-term stability of the fabricated sensing film instead of physical methods such as rf sputtering and thermal evaporation. The fabricated microsensor showed a fairly good sensing performance for CO gas in air at 250$^{\circ}C$ The sensitivity(S=Ra/Rg) was shown to be about 5 to 2000ppm CO with heating power of 50mW. -
Pt-WO
$_3$ -Si$_3$ N$_4$ -SiO$_2$ -Si-Al 캐패시터를 이용한 NO$_2$ 가스 센서를 개발하였다. 표준 실리콘 MNOS구조에 촉매 게이트로 Pt와 가스 흡착층으로 WO$_3$ 를 이용함으로서 전통적인 세라믹 가스 센서보다 낮은 온도에서 NO$_2$ 가스를 감지할 수 있었다. 은도 변화와 NO$_2$ 가스 농도의 변화에 따라서 디바이스의 NO$_2$ 가스 감도를 조사하였다. Pt-WO$_3$ 계면에서 NO$_2$ 이온농도의 변화에 기초로 한 가스 감지 모델을 제시하였다. 제시된 가스 감지 모델을 계면에서의 가스 반응 속도론에 의하여 분석함으로서 확인하였다. -
SAW filters of transversal type were fabricated on some piezoelectric substrate of the LN 128
$^{\circ}$ Y-X waters through the simulation in which the number of IDT and window function were changed for the required frequency, and the mask making. Their IDT spacing and width were 1.63$\mu\textrm{m}$ , 1.239$\mu\textrm{m}$ , respectively. Titanium thin films having different thicknesses were introduced between the Al electrode and the substrate for improving the power resistance strength due to its high temperature durability and good adhesion characteristics. All of specimens showed similar insertion loss results, which means the possibility of introducing the Ti layer though it is known to have a higher resistivity leading to a worse insertion loss result. Ti inserted specimens had a better power durability than that of pure Al electrode though their thickness had no effect on the performance. -
This study should investigate to what extent the electric field of a vacuum interrupter might be influenced by the electric potential of floating arc shield. The electric potentials of floating shield and electric fields of a vacuum interrupter are analysed by a finite element method against variation of gap distances from 1mm to 12mm. The electric potentials of floating shield was increased with the gap distance, which is because the relative position of shield is closer to fixed contact so that the capacitance distribution inside interrupter is varied. The calculated results show that the maximum value of electric field of a vacuum interrupter with floating shield is nearly same to that without shield at shorter gap distance(below 5mm), however at larger gaps a significant increment of electric field is achieved in interrupter with shield companying with model without shield, which is due to the influence of charged floating shield.
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It is analyzed the erosing process of the polymeric insulator for outdoor use with the inclined plane method. Materials used are the different type of silicone rubber, they have the content of filler and component each other. As the content of filler added to improve the tracking and erosion resistance. It has the difference of electrical performance and erosion rate. The dry-band arc is also the parameter of accelerating erosion, and appear in the form of leakage current, and the activities of leakage current has a close relationship with the surface hydrophobicity. In this paper, the erosion growth is observed by measuring the time from the voltage application to the whole breakdown, and the erosion depth. In addition, it is measured the hydrophobicity and leakage current to be a cause of erosion by the erosion steps, studied SEM, EDX for observing the transformation of surface structure by erosing.
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The purpose of this study is to research and develop solid polymer electrolyte(SPE) for Li secondary battery. This paper describes temperature dependence of conductivity, impedance spectroscopy, electrochemical properties of PVDF electrolytes as a function of a mixed ratio. Polyvinylidene(PVDF) based polymer electrolyte films were prepared by thermal gellification method of preweighed PVDF, plasticizer and Li salt. The conductivity of PVDF electrolytes was 10
$\^$ -3/S/cm. 25PVDFPC$\_$ 10/EC$\_$ 10/LiClO$_4$ electrolyte shows the better conductivity of the others. 25PVDFPC$\_$ 10/EC$\_$ 10/LiClO$_4$ electrolyte remains stable up to 4.7V vs. Li/Li$\^$ +/. Steady state current method and ac impedance used for the determination of transference numbers in PVDFD electrolyte film. The transference number of 25PVDFPC$\_$ 10/EC$\_$ 10/LiClO$_4$ electrolyte is 0.58. -
Electroluminescent(EL) devices based on organic thin films have attracted lots of interests in large-area light-emitting display. One of the problems of such device is a lifetime, where a degradation of the cell is possibly due to an organic layer's thickness, morphology and interface with electrode. In this study, light-emitting organic electroluminescent devices were fabricated using Alq
$_3$ (8-hydroxyquinolinate aluminum) and TPD(N,N'-diphenyl-N,N'-bis(3-methylphenyl)-[1-1'-biphenyl]-4,4'-diamine).Where Alq$_3$ is an electron-transport and emissive layer, TPD is a hole-transport layer. The cell structure is ITO/TPD/Alq$_3$ /Al and the cell is fabricated by vacuum evaporation method. In a measurement of current-voltage characteristics, we obtained a turn-on voltage at about 9 V. And we used other buffer layer of PPy(Polypyrrole) with ITO/PPy/TPD/Alq$_3$ /Al structure. We observed a surface morphology by AFM(Atomic Force Microscopy), UV/visible absorption spectrum, and PL(Photoluminescence) spectrum. We obtained the UV/visible absorption peak at 358nm in TPD and at 359nm in Alq$_3$ , and at 225nm and the PL peaks at 410nm in TPD and at 510nm in Alq$_3$ and at 350nm. We also studied EL spectrum in the cell structure of ITO/TPD/Alq$_3$ /Al and ITO/PPy/TPD/Alq$_3$ /Al and we observed the EL spectrum peak at 510nm from our cell -
In this paper, we have studied the effect of electron reflection on shadow mask on which tungsten oxide film is coated and have studied the variation of beam mislanding with coating thickness in CRT. We found the method to be able to control coating thicknessed and optimum coating thickness of tungsten oxide film was 1∼2
$\mu\textrm{m}$ . Mislanding of electron beam was reduced about 20∼48% with increasing coating thickness in CRT -
The scanning Maxwell-stress microscopy (SMM) is a dynamic noncontact electric force microscopy that allows simultaneous access to the electrical properties of molecular system such as surface potential, surface charge, dielectric constant and conductivity along with the topography. Here we report our recent results of its application to nanoscopic study of domain structures and electrical functionality in organic thin films prepared by the Langmuir-Blodgett technique.
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An active-matrix LCD using thin film transistors (TFT) has been widely recognized as having potential for high-quality color flat-panel displays. Pixel-Design Array Simulation Tool (PDAST) was used to profoundly understand the gate si후미 distortion and pixel charging capability. which are the most critical limiting factors for high-quality TFT-LCDs. Since PDAST can simulate the gate, data and pixel voltages of a certain pixel on TFT array at any time and at any location on an array, the effect of the resistivity of gate line material on the pixel operations can be effectively analyzed. The gate signal delay, pixel charging ratio and level-shift of the pixel voltage were simulated with varying the parameters. The information obtained from this study could be utilized to design the larger area and finer image quality panel.
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The electrical characteristics of poly-Si TFT's with offset structure by negative bias stress are systematically investigated as a function of offset length. The changes of electrical characteristics, V
$\_$ th/, off-current, on/off ratio, in the offset structured poly-Si TFT's are smaller than that of the conventional structured poly-Si TFT's under the stress condition (V$\_$ ds/=20V, V$\_$ gs/=-20V). It is found that the hot carrier effect by negative bias stress is suppressed by the offset structured poly-Si TFT's because the local electric field near the drain region is decreased by offset region. -
8
$\times$ 8 bit scaled SONOSFET NAND type flash EEPROM that shows better characteristics on cell density and endurance than NOR type have been designed and its electrical characteristics are verified with computer aided simulation. For the simulation, the spice model parameter was extracted from the sealed down SONOSFET that was fabricated by$1.5mutextrm{m}$ topological design rule. To improve the endurance of the device, the EEPROM design to have modified Fowler-Nordheim tunneling through the whole channel area in Write/Erase operation. As a result, it operates Write/Erase operation at low current, and has been proven Its good endurance. The NAND type flash EEPROM, which has upper limit of V$_{th}$ , has the upper limit of V$_{th}$ as 4.5V. It is better than that of floating gate as 4V. And a EEPROM using the SONOSFET without scaling (65$\AA$ -l65$\AA$ -35$\AA$ ), was also designed and its characteristics have been compared. It has more possibliity of error from the V$_{th}$ upper limit as 4V, and takes more time for Read operation due to low current. As a consequence, it is proven that scaled down SONOSFET is more pertinent than existing floating gate or SONOSFET without scaling for the NAND type flash EEPROM.EPROM. -
We have investigated a correlation of the electrical properties of the Pd/Ge/Pd/Ti/Au ohmic contact on n-InGaAs with its microstructures for the high temperature application of compound semiconductor devices. The samples were heat-treated by the rapid thermal annealing at various temperatures. In the contact system, moderately good specific contact resistance was obtained even before annealing because of the low metals-InGaAs barrier height, and better ohmic performances were observed by annealing up to 400˚C. But the ohmic performance was degraded after annealing at 450˚C due to the increment of Pd
$_2$ Ga$\sub$ 5/ phases. -
This paper is calculated at electron swarm simulation by Back Prolongation of Boltzmann equation for range of E/N values from 0.1~200[Td], pressure P= 1.0[Torr], temperature T=300[ 。K], the electron swarm parameter(drift velocity, longitudinal . transverse diffusion coefficients, characteristic energy, etc) in He gas is used by electron collision cross section, particularly explicate the simulation technique, and consider electrical conduction characteristic of He gas.
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This paper describes the electron transport characteristics in
$SF_6$ +He gas calculated for range of E/N values from 50~700[Td] by the Monte Carlo simulation and Boltzrnann equation method using a set of electmn collision cross sections determined by the authors and the values of electron swarm parameters are obtained by M F method. The results gained that the values of the electron swarm parameters such as the electron drift velocity, the electron ionization or attachment coefficents, longitudinal and h-ansverse diffusion coefficients agree with the experimental and theoretical for a range of E/N. -
The mechanism of methane sensing by Pd-SiC diode was investigated over the temperature range of 400~
$600^{\circ}C$ . The effects or methane gas reaction on the parameters such as barrier height, initial rate of methane gas reaction are investigated. The methane gas reaction kinetics on the device are also discussed. The physical and chemical mechanism responsible for methane detection are proposed. Analysis of steady-state reaction kinetics using I-V method confirmed that methane gas reaction processes are responsible for the barrier height change in the diode. -
The electrical characteristics of Stearic acid LB films were investigated to develop the gas sensor using Langmuir-Blodgett(LB) films. The deposition status of LB films were verified by the measurements of UV absorbance and I-V characteristics. The conductivity of Stearic acid LB films at room temperature was
$10^{-8}[S/cm]$ , which is typical of semiconductor. The conductivity was found to increase as the temperature was increased. The acitivation energy was about 1[eV]. -
Quartz crystal in contact with viscoelastic medium is described directly in terms of the electrical equivalent circuit of the system. Stearic acid is used as viscoelastic medium and deposited on the surface of quartz crystal using the Langmuir-Blodgett(LB) method. Impedance properties of quartz crystal coated with LB films which were investigated and the possibility of applying the technique to chemical sensing introduced.
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LiMn
$_2$ O$_4$ -based spinels has been studied extensively as positive electrode materials for rechargeable lithium and lithium ion batteries. We describe here that LiMn$_2$ O$_4$ cathode active materials is preparated by sol-gel process using water as solvent, which often yields inorganic oxides of excellent phase purity and well-controlled stoichiometry. Using this process, it has been possible to synthesize phase-pure crystalline spinel LiMn$_2$ O$_4$ by calcining the appropriate precursors in air at 80$0^{\circ}C$ for several hours. The influence of different time have also been explored. LiMn$_2$ O$_4$ preparated in the present study exhibit the single phase of cubic and active reaction at 400 ~$600^{\circ}C$ . Electrochemical studies show that the this method- synthesized materials appear to present reversible oxidation and reduction reactions at 3.0V ~ 4.5V and cycle stability during 50 cycle. -
The structural changes of molecules on the water surface were measured by displacement currents and
$\pi$ -A isotherm. By using a theoretical equations we calculated charges($\Delta$ Q) and dipole moment($m_{z}$ ) of saturated fatty acids($C_{12}$ ,$C_{14}$ ,$C_{16}$ ). The dynamic behavior of saturated fatty acid monolayers at the air/water interface was investigated using a displacement current-measuring technique coupled with the so called Langmuir film technique and also the dipole moment of the acids was determined.as determined.d. -
Axial magnetic field generated by special electrode construction in vacuum interrupters is used to extinguish electric plasma arcs. This investigation by FDM should prove to what extent the magnetic field might influence on the arc expansion. The calculated results show that the stronger magnetic field induced the lesser radius of arc plasma. This study will help to offer good data in design of vacuum interrupters.
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In this paper a probe for the' measurement of dielectric properties of dielectric sheet materials is designed and implemented as a coaxial air line type. Using the broadband impedance method with this measurement probe the dielectric constant and loss tangent of the glass-epoxy and teflon are determined in the frequency range of 0.1 - l.O[GHz] with the temperature variation from
$25[^{\circ}C]$ up to$65[^{\circ}C]$ . A measured relative dielectric constant of the glass-epoxy is 4.42 and a loss tangents is 0.019 relatively, and the relative dielectric constants of teflon is 2.17 and a loss tangents is 0.002 relatively -
In this paper, the physical and conductivity properties due to the electron beam irradiation for low density polyethylene using insulating materials of the distribution cable and ultra-high voltage cable are studied. The specimens of the low density polyethylene of thickness 100[
$\mu\textrm{m}$ ] irradiated as each 1 [Mrad], 2[Mrad], 4[Mrad], 8[Mrad], 16[Mrad] and virgin are used in this experiment. In order to measure the conductivity properties, the micro electrometer is used, the range of temperature and app1ying voltage are 20 to 120[$^{\circ}C$ ], from 100 to 1000[V] respectively So. as a result of the conductivity properties, it is confirmed that the conductivity is increased nearly to 50[$^{\circ}C$ ], and is not changed until the crystalline melting point from the temperature over 60[$^{\circ}C$ ] because of the defects of morphology and the formation of many trap centers by means of electron beam irradiation -
In this paper, the physical and the volume resistivity properties due to linear low density polyethylene(LLDPE)/ethylene vinyl acetate(EVA) blends are studied. In order to measure the volume resistivity properties. the micro electrometer is used, the range of temperature and applying voltage are 25 to 120[
$^{\circ}C$ ], form 100 to 1000[V] respectively. From FT-IR spectrum, LLDPE blended with EVA shows an absence of carbonyl and ether groups. From the experimental result of the volume resistivity properties, it is confirmed that the volume resistivity is decreased, which was attributed to the increase of molecular motions with the increase of temperature. -
Power capacitors are highly reliable equipment due to their completely enclosed configuration. Aging diagnosis system using partial discharge(PD) and acoustic emission(AE) is being highlighted as a research area for degradation of power capacitors. Their dielectric strength can be however reduced due to some stresses such as over-voltage or thermal degradation of the insulation material during their long period of operation. In this paper, it has been developed to express the AE of the EVENT(average amplitude) and HIT(pulse count) according to the source location. And real time measurement of PD signals for aging diagnosis of power capacitors.
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Effects of types of semicon compounds on electrical properties of XLPE were investigated. The amounts of charge of XLPE were changed with the contents of additive included in semicon electrodes, but homocharge in cathode was observed. In the aging experiment under high voltage, it was found that semiconductive layer with high impurity contents played an important role in the decrease of ACBD strength of XLPE.
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Electrical properties such as space charge distribution and electrical conduction of XLPE/VLDPE blends were studied. When the VLDPE is blended, residual charge inside XLPE increases. In case of electrical conduction characteristics, there were no changes in electrical conduction mechanism, space charge limited conduction. XLPE/VLDPE blend including crosslinking coagent showed relatively small current density. It might be due to the carbonyl group in crosslinking coagent.
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DC breakdown characteristics and formation of space charge at the interfaces of crosslinked polyethylene (XLPE) /ethylene propylene diene terpolymer (EPDM) laminates were studied. Effects of silicone grease and some chemicals such as crosslinking coagent on the interfacial charge were also studied. Interfacial charge develops at the interface of XLPE/EPDM laminates, which changes depending on heat treatment conditions and types of chemicals coated at the interface. Some chemicals such as maleic anhydride reduce the accumulation of interfacial charge in the XLPE/EPDM laminates. Breakdown strength of EPDM/XLPE laminate through the interface was highest when silicone oil was pasted in the interfaces. Interfacial breakdown strength decreased with the increase of MAH content.
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The thermal stability of polyaniline-camphorsulfonic acid(PANI-CSA) film was studied as a function of temperature and time. A decrease in electrical conductivity of PANI-CSA film occurred when PANI-CSA film is subjected to temperature above 60
$^{\circ}C$ . From the result of thermogravimetry (TG), it was thought that the deterioration in electrical conductivity of PANI-CSA film was due to evaporation of water and residual solvent. -
The space charge and conduction characteristics of chemically modified vinylpyridine (VP) grafted low density polyethylene (LDPE) was investigated. VP grafted LDPE was analyzed by elemental analysis (EA) to confirm the grafting reaction. Homocharge was developed in VP grafted LDPE at low graft ratios and changed to heterocharge with increasing the content of VP. In conduction experiment, current densities of VP grafted LDPE were lower than that of LDPE and VP grafted LDPEs showed almost the same conduction characteristics as vinylpyridine graft ratio increased
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Organic conducting N-methyl phenazinium TCNQ (7,7,8,8-tetracyanoquinonedimethane) ion radical salt was synthesized and characterized by FTIR, EA. After blending this material with PMMA using NMP/DMF, the solution was bar-coated on a PET film and dried at 40
$^{\circ}C$ . The optical micrograph showed the fibril crystals. The surface resistivity was 10$\^$ 5/$\Omega$ /$\square$ . The conductivity decreased considerably at temperatures above 80$^{\circ}C$ , although it decreased slightly at RT and 4$^{\circ}C$ . -
The interfacial breakdown between two internal dielectric surfaces represents one of the major causes of failure for power cable joint. In order to better understand this phenomenon, breakdown experiments were performed for each interfacial condition at Epoxt/EPDM interface found in cable. The specimen were Epoxy resin and EPDM generally used in cable joint. The interface conditions were three parts. First condition was the pressure of interface, we used the value of 1, 2, 3, 4, 5[kg/cm
$^2$ ]. For the second condition, the sanding condition was treated with sand paper #220, #600, #1200. Finally, we observed the breakdown according to the presence of silicon oil at the interface. -
In this study, the wind-mill type ultrasonic motor was fabricated, and then resonant frequency and vibration velocity characteristics of the stator were measured. Brass metal was pressed with umbrella-type using metal mold, then slot of 4 kind was processed in each of thickness. Among sixteen's stators, resonant frequency on vibration velocity was decreased remarkably in stator of higher resonant point, but resonant frequency on vibration velocity wasn't almost changed at lower resonant point of stator. The thickener thickness of elastic body, vibration velocity was decreased. The more slot of elastic body, vibration velocity was increased Applied voltage was changed from 10
$V_{max}$ to 100$V_{max}$ . Maximum vibration velocity value was 2.0[m/s]. -
In this study, the cymbal actuators with brass and bronze endcap at various endcap thickness were fabricated, and then the displacement vs applied voltage relation and position from the center of endcap relation were investigated The displacement values of all cymbal actuator were measured using laser vibrometer. The displacement of the cymbal actuator was increased linearly with increasing applied voltage. The cymbal actuator with 0.15mm thick brass endcap show approximately 1.3
$\mu\textrm{m}$ displacement more than cymbal actuator with uniformly thick bronze endcap. The displacement about 3mm in diameter at the center of the endcap was uniform and rapidly decreased away from 3mm in diameter at the center of the endcap. -
The (S
$r_{0.85}$ C$a_{0.15}$ )Ti$O_3$ (SCT) thin films are deposited on Pt-coated electrode using RF magnetron sputtering method at various substrate temperature. Dielectric constant of SCT thin films is increased with increased as the deposition temperature and changes almost linearly in temperature ranges from -80 to +90[$^{\circ}C$ ]. The drastic decrease of dielectric constant and increase of dielectric loss in SCT thin films is observed above 200[kHz]. V-I characteristics of SCT thin films show the increasing leakage current with the increases of deposition temperature.ure. -
(Ba, Sr)TiO
$_3$ [BST] thin films were fabricated on Pt/SiO$_2$ /Si substrate by RF sputtering technique. The structural, dielectric and electrical properties of BST thin films were investigated with Ar/O$_2$ ratio. Dielectric constant and dielectric loss of the BST thin film were about 1020 and 2.0[%], respectively. (at RF power 80W, post annealing temperature$650^{\circ}C$ , deposition pressure of 5mTorr and Ar/O$_2$ =80/20). For the BST(Ar/O$_2$ =80/20) thin film with Polarization switching cycles of 10$^{10}$ , remanent polarization and coercive field were 0.084[$\mu$ C/cm$^2$ ], 1.954[kV/cm], respectively. -
Ferroelectric PZT(10/90)PZT(90/10) heterolayered thin films were fabricated by spin-coating method on the Pt/Ti/SiO
$^2$ /Si substrate alternately using PZT(10/90) and PZT(90/10) metal alkoxide solutions. The coating and heating procedure was repeated six times to form PZT heterolayered films. The surface, cross-sectional microstructures and thickness of the films were observed using scanning electron microscope(SEM). The relative dielectric constant and dielectric loss of the 5-coated PZT heterolayered films were 1331 and 4.8% respectively. -
The (
$0.8BaTiO_3-0.1SrTiO_3-0.1MgTiO_3$ )+$0.006Nb_2O_5$ ceramics were fabricated by conventional ceramic process. The dielectric property of specimen was investigated that the specimen was sintering temperature at 1,300C for 3hours and then annealed at$1,100^{\circ}C$ for 3hours in a atmosphere (air) to be painted on the surface with CuO paste. The results of the temperature and frequency are varied, the dielectric constant and loss tangent are unsuitable for BL capacitor. The dielectric constants were varied to be negative temperature coefficient(2.000-3,000) in the temperature range between -10 and$140^{\circ}C$ , the dissipation factors (tan$\delta$ ) were some high(0.1-0.3). It was not grain insulation, in cause of the some difficult to be annealed temperature with CuO paste and fired atmosphere. But, we have some different annealing temperature and fired atmosphere, it will be suitable BL(Boundary Layer)capacitor. -
In this paper. we designed and simmulated a ring-dot type piezoelectric transformer. As the result, piezoelectric transformer of
25${\times}25{\times}3.5mm$ size (Dot electrode diameter of Ilmm) show the maximum displacement, stress and output power. When the Input voltage of piezoelectric transformer was 155V. Output voltage show 30V and output power 9W at the load resistance of$100\Omega$ -
PbTi
$O_3$ family ceramics can be used for the piezoelectric transformer using thickness extensional vibration mode because it is a material with the large anisotropy between electromechanical coupling factors$k_{t}$ and$k_{p}$ . However, PbTi$O_3$ family ceramics have a difficult poling condition on account of its large anisotrophy. In this study, the structural and piezoelectric properties of (P$b_{0.76}$ $Ca_{0.24}$ )[$Ti_{0.96}$ (M$n_{1}$ 3/S$b_{2/3}$ )$_{0.04}$ ]$O_3$ system ceramics were investigated as a function of poling voltage in order to find the best poling condition.ion.n.n.ion.n. -
ZnO varistors have an excellent non-linearity and a large surge-energy absorption capability. For these reasons, the ZnO varistors are widely used to protect electrical/electronic circuits from an abnormal surge and/or noise signal. In order to obtain the low-voltage varistor with randomly distributed large seed grain within bulk, the ZnO varistors are made by a new three-composition seed grain method. And a conduction mechanism of varistors, which was observed in the temperature range of 30 ∼ 120
$^{\circ}C$ and at the current range of 10$\^$ -8/∼10$^2$ A/cm$^2$ , was classified by the three regions of different mechanism when the current was increased. -
We measured the dielectric properties with YMnO
$_3$ ceramics using solution method based procedure via by citrate. The crystalline phases were determined using XRD. Also we observed morphologies of YMnO$_3$ ceramics using SEM. We proved the structure of YMnO$_3$ ceramics which is hexagonal. But lots of pores were observed the microstructure. It would be considered as volatile organic. The maximum density of YMnO$_3$ ceramics is obtained sintering temperature 135$0^{\circ}C$ and the ratio 0.95/1.05 of Y/Mn. But even though the density we obtained is the highest, that is lower than theoretical density because of remaining organics by citric acid. Dielectric constant and dissipation factor were improved as increasing sintering temperature and the Y/Mn ratio (0.95/1.05) -
Metallic ferromagnet LA
$_{1-x}$ Sr$_{x}$ MnO$_3$ has received considerable attentions because of its metallic conductivity and giant magnetic resistivity. It is generally believed that layered perovskite SrO(LA$_{1-x}$ Sr$_{x}$ MnO$_3$ )$_{n}$ phase is insulating and shows no metallic transition. But recent report revealed that some single crystal SrO(LA$_{1-x}$ Sr$_{x}$ MnO$_3$ )$_{n}$ phase showed MR effect. In this study, layered perovskite SrO(LA$_{1-x}$ Sr$_{x}$ MnO$_3$ )$_2$ Phases were synthesized by solid state reaction at 140$0^{\circ}C$ in air atmosphere, for wide range of x and their phases were confirmed by X-ray diffraction. Electrical and magnetic properties were measured down to 10K and the possibility of MR effects was investigated.as investigated. -
The influence of
$WO_3$ (0.5-4.0mol%) on the microstructural and electrical properties of ZnO varistors was investigated. The major part of a tungsten segregated to the nodal point. SEM, EDAX, and XRD analysis revealed that three phase, such as W-rich phase, Bi-rich phase, and spinel phase, coexist at the nodal point. The average grain size increased in the range of 15.5-29.9pm with increasing$WO_3$ content. This may be probably attributed to liquid phase formed by$WO_3$ ,$WO_3$ acted as promotion additive of grain growth. As$WO_3$ content increase, the varistor voltage greatly decreased in the range 186.82-35.87V/mm due to the increase of grain growth. The barrier height decreased in the range 1.93-0.42eV with increasing$WO_3$ content. -
The microstructure and conduction characteristics of ZnO varistor fabricated in the range of 0.0 ~ 4.0mol%
$Y_20_3$ were investigated. With increasing$Y_20_3$ content, distribution of spinel phase decreased, whereas Y-rich phase segregated to the nodal point increased, as a result, the average grain size decreased in the range of$20.0 ~ 4.8{\mu}m$ .$Y_20_3$ content showing relatively good conduction characteristics was l.Omol%, then nonlinear exponent and leakage current was 55.3, 0.66mA.respectively. -
It was investigated that the dielectric properties of ferroelectric materials using PZT-5A and PZT thin films. PZT-5A was 20mm diameters, 0.71mm, 0.51mm and 0.41mm thickness respectively and having c-axis preferred orientation. Electrodes(Al) were deposited by evaporation method. PZT thin film was deposited on Pt/SiO
$_2$ /Si substrate by RF magnetron sputtering method, and annealed at 750$^{\circ}C$ with RTA. Dielectric constants were measured automatically by computer measuring system. Dielectric constants were changed rapidly from 817 to 888 in 0.41mm thickness PZT-5A, 823 to 890 in 0.51mm and 822 to 839 in 0.71mm as the electric field grown. In the case of PZT thin film, dielectric constants were changed from 724 to 1173 in 4500${\AA}$ thickness, 721 to 1204 in 5500${\AA}$ thickness and 811 to 1407 in 7000${\AA}$ thickness. -
The objective of this study is to deposited the preparation of STO dielectric thin films on Ag/barrier-mater/Si(N-type 100) bottom electrode using a conventional rf-magnetron sputtering technique with a ceramic target under various conditions. It is demonstrated that the leakage current of films are strongly dependent on the atmosphere during deposition and the substrate temperature. The resistivity properties of films deposited on silicon substrates were very high resistivity. Capacitance of the films properties were the highest value(1000pF) and dependent on substrate temperature.
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We have investigated ionic conductivity and electrochemical stability of the electrolytes containing organic solvent. Ion conductivities were measured between 10 and 80
$^{\circ}C$ , and electrochemical stabilities were determined by cyclic voltammetry on glassy carbon, platinum and aluminum electrodes. Ionic conductivity of electrolyte(EC:DEC=1:1) with IM LiPF$\_$ 6/ shows better than that of the other electrolytes having Li salts. The IM LiBF$_4$ -PC electrolyte exhibits good electrochemical stability. IM LiPF$\_$ 6/ (EC:DEC=1:1) and IM LiPF$\_$ 6/ (EC:DMC=1:1) electrolytes are used for the high capacity of battery system. -
Electroluminescent(EL) devices based on organic materials have been of great interest due to their possible applications for large-area flat-panel displays. They are attractive because of multicolor emission low operation voltage. In this study, several Eu complexes such as Eu(TPB)
$_3$ (Phen) and Eu(TPB)$_3$ (Bpy) were synthesized and the photoluminescence(PL) and electroluminescence (EL) characteristics of their thin films were investigated by fabricating the devices having a structure of glass substrate/ITO/TPD/Europium-complexs/Alq$_3$ /Al, where aromatic diamine(TPD) was used as an hole transporting and Alq$_3$ was used as an electron transporting materials. It was found that the photoluminescence(PL) and electroluminescence(EL) characteristics of these Europium complexes were dependent upon the ligands coordinated to Europium metal. Details on the explanation of electrical transport phenomena of the structure with I-V characteristics of the OLEDs using the trapped-charge-limited current(TCLC) model will be discussed. -
Electroluminescence is occurred when phosphor is located in electric field. Object of this research show powder electroluminescent device (PELD) for high brightness compared with conventional PELD. Single layer of PELD structured as follow (ITO/phosphor + dielectric/silver paste). To investigate optical properties of PELDS, EL spectrum, CIE coordinate system, Brightness of PELDs was measured. The suitable ratio between phosphor and dielectric in single layer of PELD was 7:3(phosphor: dielectric). At 200 V4OO Hz, high performance of PELD which had ratio of 7:3
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In this paper,
$Al_2$ O$_3$ /MgO belayer was prepared with Electron-beam evaporation and the properties of the film was investigated in order to improve the property of MgO film, which is used for the protection layer in PDP(Plasma Display Panel).$Al_2$ O$_3$ /MgO belayer were improved of roughness and it were condensed by annealing, and the result of XPS analysis for$Al_2$ O$_3$ /MgO belayer unchanged binding energy. To investigate electric characteristics, discharge properties of$Al_2$ O$_3$ /MgO belayer were compared with discharge minimum voltage for MgO monolayer through Ar discharge experiments. -
The effects of the additions of transition metal oxides on ZrO
$_2$ - Y$_2$ O$_3$ (Y$_2$ O$_3$ - containing tetragonal zirconia polycrystals : Y-TZP) system has been studied by investigating fracture toughness and phase stability of the sintered specimens. In the specimens sintered at 1450$^{\circ}C$ for 2hrs in air the phase transformation from tetragonal to monoclinic was observed. The ratios of monoclinic phase to tetragonal phase were changed with the additions of CoO, Fe$_2$ O$_3$ and MnO$_2$ , respectively, from 0.00 to 8.00wt%. The fracture toughness was increased with increasing the monoclinic to tetragonal phase ratio and was maximum at the ratio of about 18%. However, the hardness was decreased with increasing the ratio. The additions of CoO, Fe$_2$ O$_3$ and MnO$_2$ together into Y-TZP resulted in more complex behaviors of fracture toughness and hardness. The specimen with the additions of 1.5wt% Fe$_2$ O$_3$ , 3.0wt% Al$_2$ O$_3$ and 1.5wt% CoO showed the monoclinic to tetragonal phase ratio of 18% and the highest toughness of 10.8 MPa.m$\^$ $\frac{1}{2}$ / and Vickers hardness of 1201kgf/mm$^2$ . -
Organic light-emitting diodes(OLEDs) or electroluminescent devices have attracted much attention because of their possible application as large-area light-emitting displays. Their structure was based on employing a multilayer device structure containing an emitting layer and a carrier transporting layer of suitable organic materials. In this study, several Tb complexes such as Tb(ACAC)
$_3$ (Phen), Tb(ACAC)$_3$ (Phen-Cl) and Tb(TPB)$_3$ (Phen) were synthesized and the photoluminescence(PL) and electroluminescence (EL) characteristics of their thin films were investigated by fabricating the devices having a structure of anode/HTL/terbium-oomplex/ETL/cathode, where TPD was used as an hole transporting and Alq$_3$ and TAZ-Si were used as an electron transporting materials. It was found that the photoluminescence(PL) and electroluminescence(EL) characteristics of these terbium complexes were dependent upon the ligands coordinated to terbium metal. Details on the explanation of electrical transport phenomena of the structure with I-V characteristics of the OLEDs using the trapped-charge-limited current(TCLC) model will be discussed. -
Many researchers make efforts to develop an effective material with anti-degradation property. Specially, the porcelain type insulator is required exchanging to polymer insulator acceding to the environmental consideration In this paper, we have developed the estimation system using the PD testing. The approach of PD has been very successful applied to the various practical insulator.
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The current-voltage characteristic have been measured in a gas stabilized DC arc generated in a non-transferred arc plasma torch operating on a mixture of argon and nitrogen. Relation between voltage and current to these arcs has been examined by plasma power and current under different flow rates and gas mixture ratios. Firstly, the voltage and current of arc plasma used argon was measured and secondly, in argon-nitrogen mixed gas regime, the flow rate of nitrogen was increased slowly. When the flow rate of nitrogen was increased, electrode drop of potential was increased.
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The stability of the properties of magnetite particles in novel medicinal magnetic ointments of multipurpose application was examined by Mossbauer spectroscopy. Comparative analysis of the results obtained by model fitting of
$\^$ 57/Fe nuclei spectra with those known for the system Fe$_3$ O$_4$ -${\gamma}$ -Fe$_2$ O$_3$ allowed to identify the phase composition of the particles. This composition, as well as that of the initial pure component in the form of a highly dispersed fraction (∼ 100${\AA}$ ), differs noticeably from the stoichiometric one. Despite their small sizes, the particles exhibit no superparamagnetism ( in the temperature range from 95 to 300k ). Radiative sterilization of the ointments has no effect on the magnetic component composition. -
Park, Gye-Choon;Im, Young-Sham;Chung, Hae-Duck;Lee, Jin;Chung, In-Sung;Kim, Jong-Uk;Gu, Hal-Bon 331
Crystal structure and surface morphology of Se thin film fabricated by EBE method had been studied. Se thin film was deposited with amorphous structure until substrate temperature of l00$^{\circ}C$ . But Se thin film was grown with monoclinic structure at substrate temperature af over 150$^{\circ}C$ , and its lattice constant of a, b and c was 12.76${\AA}$ , 9.15${\AA}$ and 10.41${\AA}$ respectively. Also, after heat-treatment at 150。 for 15 min with substrate temperature of l00。, amorphous Se was proved to be hexagonal structure, and its lattice constant of a and c was 4.27${\AA}$ and 4.83${\AA}$ respectively. -
Ferroelectric Sr
$_2$ (Nb,Ta)$_2$ O$_{7}$ (SNTO) thin films were prepared by chemical solution deposition processes. SNTO thin films were spin-coated on Pt/Ti/SiO$_2$ /(100)Si substrates. After multiple coating, dried thin films were heat-treated for decomposition of residual organics and crystallization. B site-rich impurity phase, i.e. [Sr(Nb,Ta)$_2$ O$_{6}$ ], was found after annealing, where its appearance was dependent on process temperature indicating the possible reaction with substrate. Dielectric and other relevant electrical properties were measured and the results showed a little possibility in ferroelectric gate random access memory devices.s.s. -
Ferroelectric L
$a_2$ $Ti_2$ $O_{7}$ (LTO) thin films were prepared by chemical solution deposition processes. Acetylacetone was used as chelating agent and nitric acid was added in the stock solution to control hydrolysis and condensation reaction rate. The LTO thin films were spin-coated on Pt/Ti/$SiO_2$ /(100)Si and Pt/Zr$O_2$ /$SiO_2$ /(100)Si substrates. After multiple coating, dried thin films were heat-treated for decomposition of residual organics and crystallization. The role of acetylacetone in Ti iso-propoxide stabilization by possibly substituting$O^{i}$ Pr ligand was studied by H-NMR. B site-rich impurity phase, i.e. L$a_4$ $Ti_{9}$ $O_{24}$ , was found after annealing, where its appearance was dependent on process temperature indicating the possible reaction with substrate. Dielectric and other relevant electrical properties were measured and the results were compared between modified sol-gel and MOD processes.s.s. -
The generation of pretilt angle in nematic liquid crystal (NLC) and electro-optical (EO) characteristics of photo-aligned twisted nematic (TN)-LCD with oblique P-polarized ultraviolet (UV) light irradiation on the two kinds of the soluble polyimide (PI) surfaces containing trifluoromethyl moieties were investigated. The generated pretilt angle of NLC is about 2.5
$^{\circ}$ with P-polarized UV light irradiation of 20$^{\circ}$ on PI-3 surface at 20 min.; However pretilt angle of about 0.5$^{\circ}$ are observed on PI-1 and PI-2 surfaces. The generated pretilt angle of NLC on PI-3 surface may be attributed to the trifluoromethyl moieties attached to the lateral benzene rings. The voltage-transmittance and response time characteristics of photo-aligned TN-LCD with P-polarized UV light irradiation of 20$^{\circ}$ on PI-1 surface at 20 min were almost same in comparison with the rubbing-aligned TN-LCD. However, the high threshold voltage and slow response are observed on PI-3 surface. Also, the decay time$\tau$ $\sub$ d/ of photo-aligned TN-LCD is attributed to the anchoring energy of NLC.