• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.108-111
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• 2009

We have determined the electronic energy level alignment at the interface between 4,4'-bis-N-phenyl-1-naphthylamino biphenyl (NPB) and 1,4,5,8,9,11-hexaazatriphenylenehexacarbonitrile (HAT-CN) using ultraviolet photoelectron spectroscopy (UPS). The highest occupied molecular orbital (HOMO) of 20 nm thick HAT-CN film was located at 3.8 eV below the Fermi level. Thus the lowest unoccupied molecular orbital (LUMO) is very close to the Fermi level. The HOMO position of NPB was only about 0.3 eV below Fermi level at NPB/HAT-CN interface. This enables an easy excitation of electrons from the NPB HOMO to the HAT-CN LUMO, creating electron-hole pairs across this organic-organic interface. We also study the interaction of HAT-CN with a few metallic surfaces including Ca, Cu, and ITO using UPS and ab-inito electronic structure calculation techniques.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.06a
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• pp.75-78
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• 1998

The SONOSFET Shows low operation voltage, high cell density, anti good endurance due to modified Fowler-Nordheim tunneling as memory charge injection method. In this paper, therefore, the NOR-type Flash EEPROM composed of SONOSFET, which has fast lead operation speed and Random Access characteristics, is proposed. An 8${\times}$8 bit NOR-type SONOSFET Flash EEPROM had been designed and its electrical characteristics were verified. Read/Write/Erase operations of it were verified with the spice parameters of SONOSFETs which had Oxide-Nitride-Oxide thickness of 65${\AA}$-165${\AA}$-35${\AA}$ and that of scaled down as 33${\AA}$-53${\AA}$-22${\AA}$, respectively. When the memory window of the scaled-down SONOSFET with 8V operation was similar to that of the SONOSFET with 13V operation, the Read operation delay times of the scaled-down SONOSFET were 25.4ns at erase state and 32.6ns at program state, respectively, and those of the SONOSFET were 23.5ns at erase state and 28.2ns at program state, respectively.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.14 no.4
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• pp.32-40
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• 2005

The purpose of this study is to investigate variation of spark plug protrusion and PDA valve on the exhaust emission in a gasoline engine. Swirl is one of the important parameters that affects the characteristics of combustion. PDA valve has been developed to satisfy requirements of sufficient swirl generation for improving the combustion and reducing of emission level. Also, especially, the variation of spark plug protrusion have an important effect to the early flame propagative process. This is largely due to the high flame speed by short of flame propagation distance. So, this is forced that injection timing, spark timing and intake air motion govern the stable combustion. As a result, using two combustion chamber, without charge of engine specification and the variable spark plug location and PDA valve could be reduced exhaust gas at a part load engine conditions(1500rpm imep 3.9bar, 2000rpm imep 3.2bar, 2400rpm imep 3.9bar).

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.5
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• pp.170-175
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• 2003

A control algorithm is developed for highly efficient operation of auxiliary power unit (APU) that consists of a diesel engine and a directly coupled induction generator in series hybrid electric Bus (SHEB). In a series hybrid configuration the APU supplies the electric power needed for maintaining the state of charge (SOC) of the battery unit in various conditions of vehicle operation. As the rotational speed of generator does not depend on the vehicle speed, an optimized operation of engine-generator unit based on the efficiency map of each component can be achieved. The output torque of diesel engine can be controlled by the amount of fuel injection, and the power converted from mechanical to electrical energy can be adjusted by generate control unit (GCU) using the decoupling vector control of torque and flux. As for the given reference of the generating power, the multiply of speed and torque, many combinations of operating speed and torque are possible. The algorithm decides the new operating point based on the engine efficiency map and generator characteristic curve. During the transition of operating points, the speed controller saturation is avoided using variable limit and filtering of generator torque reference. A test rig and SHEB consist of a 1.5L diesel engine and a 30kw induction generator are constructed by Hyundai Motor Company.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.51 no.1
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• pp.23-28
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• 2002

In order to survey the radiation characteristics of pure line noise of unwanted noise from overhead high voltage AC transmission lines, a disk type gap noise generator was manufactured. Disk size which decides capacitance between the noise generator and earth was selected through preliminary indoor experiments and analysis by using surface charge method. The capacitance is one of principal parameters related to the injection of a proper noise current into lines. On the basis of the capacitance obtained from calculation, 5mm of space was given to the gap of the noise generator to be installed o test line and an aluminum disk of 60cm radius was made. The field experiments were performed with the noise generator hung on the Kochang 765 kV full scale test line. As the results, the useful data which can be used to analysis the radiation characteristics of noise from transmission lines were obtained. Those are the directivity of antenna toward the line, lateral profiles, frequency spectra, height pattern and so on.

• Electrical & Electronic Materials
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• v.7 no.3
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• pp.231-235
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• 1994

The multi-dielectric layer $SiO_2$/$Si_3{N_4}$/$SiO_2$ (ONO) is used to improve charge retention and to scale down the memory device. The nitride layer of MNOS device is oxidize to form ONO system. During the oxidation of the nitride layer, the change of thickness of nitride layer and generation of interface state between nitride layer and top oxide layer occur. In this paper, effects of oxidation of the nitride layer is studied. The decreases of the nitride layer due to oxidation and trapping characteristics of interface state of multi layer dielectric film are investigated through the C-V measurement and F-N tunneling injection experiment using SONOS capacitor structure. Based on the experimental results, carrier trapping model for maximum flatband voltage shift of multi layer dielectric film is proposed and compared with experimental data. As a results of curve fitting, interface trap density between the top oxide and layer is determined as being $5{\times}10^11$~$2{\times}10^12$[$eV^1$$cm^2$].

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.04a
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• pp.31-34
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• 2004

During the last 20 years organic semiconductors have attracted considerable attention due to their interesting physical properties followed by various technological applications in the area of electronics and opto-electronics. It has been a long time since organic solar cells were expected as a low-cost energy-conversion device. Although practical use of them has not been achieved, technological progress continues. Morphology of the materials, organic/inorganic interface, metal cathodes, molecular packing and structural properties of the donor and acceptor layers are essential for photovoltaic response. We have fabricated solar cell devices based on zinc-phthalocyanine(ZnPc) as donor(D) and fullerine$(C_{60})$ as electron acceptor(A) with doped charge transport layers, $Alq_3$ as an electron transport or injection layer. We observed the photovoltaic characteristics of the solar celt devices using the Xe lamp as a light source.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.7
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• pp.539-544
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• 2010

We have synthesized new blue electroluminescent polyalkylfluorene-based copolymers [poly(F-co-Py)x:y, where x:y = 99:1 or 95:5 mole ratios] containing the hole-injecting pyrazole derivative [3,3'-(4,6-bis(octyloxy)-1,3-phenylene)bis(1,5-diphenyl-4,5-dihydro-1H-pyrazole] through Ni(0) mediated polymerization, and their electroluminescent properties were investigated. Electroluminescent (EL) devices were fabricated with ITO / PEDOT:PSS (110 nm) / copolymers or PF homopolymer (80 nm) / Ca (50 nm) / Al (200 nm) configuration. Each EL device constructed from the copolymer exhibited significantly enhanced brightness and efficiency compared with a device constructed from the PF homopolymer. The EL device constructed with poly(F-co-Py)99:1 exhibited the highest luminous efficiency and brightness (0.95 cd/A and $2,907\;cd/m^2$, respectively). The achieved luminous efficiency was an excellent result, providing almost a 4-fold improvement on the efficiency obtainable with the a PF homopolymer device. This enhanced efficiency of the copolymer devices results from their improved hole injection and more efficient charge carrier balance, which arises from the HOMO level (~5.83 eV) of the poly(F-co-Py)99:1 copolymer, which is higher than that of the PF homopolyme (~5.90 eV).

• Journal of Soil and Groundwater Environment
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• v.20 no.2
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• pp.41-46
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• 2015

The drag of the excess charge in an electrical double layer at the solid fluid interface due to water flow induces the streaming current, i.e., the streaming potential (SP). Here we introduce a sandbox experiment to study this hydroelectric coupling in case of a tracer test. An acrylic tank was filled up with homogeneous sand as a sand aquifer, and the upstream and downstream reservoirs were connected to the sand aquifer to control the hydraulic gradient. Under a steady-state water flow condition, a tracer test was performed in the sandbox with the help of peristaltic pump, and tracer samples were collected from the same interval of five screened wells in the sandbox. During the tracer test, SP signals resulting from the distribution of 20 nonpolarizable electrodes were measured at the top of the tank by a multichannel meter. The results showed that there were changes in the observed SP after injection of tracer, which indicated that the SP was likely to be related to the solute transport.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.129.2-129.2
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• 2013

Electron injection enhancement at OLED (organic light-emitting diodes) cathode side has mostly been achieved by insertion of a low work function layer between metal electrode and emissive layer. We investigated the interfacial chemical reactions and electronic structures of alkaline-earth metal (Ca, Ba)/Alq3 [tris(8-hydroxyquinolinato)aluminium] and Ca/BaF2/Alq3 using in-situ X-ray & ultraviolet photoelectron spectroscopy. The alkaline-earth metal deposited on Alq3 generates two energetically separated gap states in sequential manner. This phenomenon is explained by step-by-step charge transfer from alkali-earth metal to the lowest unoccupied molecular orbital (LUMO) states of Alq3, forming new occupied states below Fermi level. The BaF2 interlayer initially prevents from direct contact between Alq3 and reactive Ca metal, but it is dissociated into Ba and CaF2. However, as the Ca thickness increases, the Ca penetrates the interlayer to directly participate in the reaction with underlying Alq3. The influence of the multiple gap state formation by the interfacial chemical reaction on the OLED performance will be discussed.