• 한국자기학회:학술대회 개요집
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• 한국자기학회 2003년도 하계학술연구발표회 및 한.일 공동심포지엄
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• pp.150-151
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• 2003

In the past years, a giant magnetoresistance (GMR) effect found in perovskite-like structured materials has attracted considerable attention among scientists and manufacturers, since, a practical point of view, the capacity of producing magnetic and sensing sensors. In a stream of this interest, further efforts to understand the underlying mechanism that leads to the GMR effect relative to the correlation between transport and magnetic properties, have been extensively devoted. In these cases, spin-glass-like behaviors are ascribed to the frustration of random competing exchange interactions, namely the ferromagnetic double-exchange interaction between Co$\^$3+/ (or Mn$\^$3+/) and Co$\^$4+/(or Mn$\^$4+/) and the antiferromagnetic one like spins. Noticeably, the distinction of spin-glass region from cluster-glass one, involved in the remarkable changes in transport and magnetic properties at a critical value of doping concentration, was observed. Magnetic anomalies in zero-field-cooled (ZFC) magnetization as well as ac magnetic susceptibility below Curie temperature T$\sub$c/ and the charge/orbital fluctuation were also realized. In this work, we present a study of magnetic properties of a deficient manganese perovskites system of La$\sub$0.6/Sr$\sub$x/MnTi$\sub$y/O$_3$, and particularly provide its new magnetic phase diagram.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 추계학술대회 논문집 Vol.15
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• pp.534-537
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• 2002

We have studied conduction mechanism that is interpreted in terms of space charge limited current (SCLC) region and tunneling region. The OLEDs are based on the molecular compounds, N,N'-diphenyl-N,N'-bis(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine (TPD) as a hole transport, tris (8- hydroxyquinolinoline) aluminum(III) $(Alq_3)$ as an electron injection and transport and emitting later, copper phthalocyanine (CuPc) and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and poly(vinylcarbazole) (PVK) as a buffer layer respectively. Al was used as cathode. We manufactured reference structure that has in ITO/TPD/$Alq_3$/Al. Buffer layer effects were compared to reference structure. And we have analyzed out luminance efficiency-voltage characteristics in ITO/Buffer layer/TPD/$Alq_3$/Al with buffer-layer materials.

• Transactions on Electrical and Electronic Materials
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• 제16권3호
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• pp.151-155
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• 2015

We fabricated the Cu Schottky contact on an n-type Ge wafer and investigated the forward bias current-voltage (I-V) characteristics in the temperature range of 100~300 K. The zero bias barrier height and ideality factor were determined based on the thermionic emission (TE) model. The barrier height increased and the ideality factor decreased with increasing temperature. Such temperature dependence of the barrier height and the ideality factor was associated with spatially inhomogeneous Schottky barriers. A notable deviation from the theoretical Richardson constant (140.0 Acm^-2K^-2 for n-Ge) on the conventional Richardson plot was alleviated by using the modified Richardson plot, which yielded the Richardson constant of 392.5 Acm^-2K^-2. Finally, we applied the theory of space-charge-limitedcurrent (SCLC) transport to the high forward bias region to find the density of localized defect states (N_t), which was determined to be 1.46 × 10¹² eV^-1cm^-3.

• Transactions on Electrical and Electronic Materials
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• 제18권2호
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• pp.89-92
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• 2017

The performance of three-layered organic light-emitting diodes (OLEDs) was investigated using TPD hole-transport and injection layers, Teflon-AF, and the electron-injection layer of $Li_2CO_3$ and LiF. The OLEDs were manufactured in a structure of TPD/$Alq_3$/LiF, TPD/$Alq_3$/$Li_2CO_3$, and AF/$Alq_3$/LiF using low-molecular organic materials. In three different three-layered OLEDs, it was found that the device with the TPD/$Alq_3$/LiF structure shows higher performance in maximum luminance, and maximum external quantum efficiency compared to those of the device with TPD/$Alq_3$/$Li_2CO_3$ and TPD/$Alq_3$/LiF by 35% and 17%, and 193% and 133%, respectively. It is thought that the combined LiF/Al cathode contributes to a reduced work function and improves an electrical conduction mechanism due to the electron injection rather than the hole transport, which then increases a recombination rate of charge carriers.

• 반도체디스플레이기술학회지
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• 제20권1호
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• pp.54-58
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• 2021

The RGO with controllable oxygen functional groups is a novel material as the active layer of resistive switching memory through a reduction process. We designed a nanoscale conductive channel induced by local oxygen ion diffusion in an Au / RGO+GQD / Al resistive switching memory structure. A strong electric field was locally generated around the Al metal channel generated in BIL, and the local formation of a direct conductive low-dimensional channel in the complex RGO graphene quantum dot region was confirmed. The resistive memory design of the complex RGO graphene quantum dot structure can be applied as an effective structure for charge transport, and it has been shown that the resistive switching mechanism based on the movement of oxygen and metal ions is a fundamental alternative to understanding and application of next-generation intelligent semiconductor systems.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.207.1-207.1
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• 2014

High-mobility and two dimensional conduction at the interface between two band insulators, LaAlO3 (LAO) and SrTiO3 (STO), have attracted considerable research interest for both applications and fundamental understanding. Several groups have reported the photoconductivity of LAO/STO, which give us lots of potential development of optoelectronic applications using the oxide interface. Recently, a giant photo response of Pd nano particles/LAO/STO is observed in UV illumination compared with LAO/STO sample. These phenomena have been suggested that the correlation between the interface and the surface states significantly affect local charge modification and resulting electrical transport. Water and gas adsorption/desorption can alter the band alignment and surface workfunction. Therefore, characterizing and manipulating the electric charges in these materials (electrons and ions) are crucial for investigating the physics of metal oxide. Proposed mechanism do not well explain the experimental data in various ambient and there has been no quantitative work to confirm these mechanism. Here, we have investigated UV photo response in various ambient by performing transport and Kelvin probe force microscopy measurements simultaneously. We found that Pd nano particles on LAO can form Schottky contact, it cause interface carrier density and characteristics of persistence photo conductance depending on gas environment. Our studies will help to improve our understanding on the intriguing physical properties providing an important role in many enhanced light sensing and gas sensing applications as a catalytic material in different kinds of metal oxide systems.

• 화약ㆍ발파
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• 제30권1호
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• pp.29-36
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• 2012

기폭위치가 지반진동에 미치는 영향에 대한 연구들을 살펴보면 발파진동의 복합적인 원인에 반하여 단편적인 연구로 진행되거나 적용범위가 연구가 이루어진 해당 현장만으로 국한적으로 나타나며 발파설계 인자로서 이용되는 데 한계를 보였다. 이에 본 연구는 기폭위치에 따라 발파진동의 전파 특성을 파악하기 위해서 공간격, 저항선, 천공장 그리고 장약량 등을 달리하여 총 72회의 단일공 시험발파를 실시하여 발파진동 예측식을 도출하였다. 도출된 발파진동 예측식으로부터 기폭위치에 따른 최대입자속도의 노모그램 분석을 통해 진동특성을 규명하였다. 또한, 국토해양부의 "도로공사 노천발파 설계 시공 지침"에 제시된 표준발파공법의 공법별 경계 기준 장약량인 0.5, 1.6, 5, 15kg을 적용하여 기폭위치별 진동 감쇄경향을 비교 분석하여 발파설계의 인자로 사용할 수 있도록 제안하였다.

• 대한화학회지
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• 제37권1호
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• pp.10-21
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• 1993

2-hydroxyethyl methacrylate(HEMA)을 중합한 P(HEMA)막을 통하여 10가지 아미노산들의 확산계수, 분배계수 및 투과도를 용액의 pH 변화하에서 조사 연구하였다. 아미노산의 투과도는 각 아미노산들의 분자형태, 분자크기 및 전하량에 따라 다른 값을 나타냄을 확인하였으며, 특히 용액의 pH에 따라 전하량이 변화하는 각 아미노산은 P(HEMA)막을 통하여 투과시킬 때 모든 아미노산이 중성영역용액에서 가장 많이 투과되고 이때 막은 미세공막으로 작용하며, 염기성영역용액에는 산성영역용액보다 더 많이 투과되고 막은 분배막으로 작용함을 알았다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.27-27
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• 2011

For the design of real applicable molecular devices, current-voltage properties through molecular nanostructures such as metal-molecule-metal junctions (molecular junctions) have been studied extensively. In thiolate monolayers on the gold electrode, the chemical bonding of sulfur to gold and the van der Waals interactions between the alkyl chains of neighboring molecules are important factors in the formation of well-defined monolayers and in the control of the electron transport rate. Charge transport through the molecular junctions depends significantly on the energy levels of molecules relative to the Fermi levels of the contacts and the electronic structure of the molecule. It is important to understand the interfacial electron transport in accordance with the increased film thickness of alkyl chains that are known as an insulating layer, but are required for molecular device fabrication. Thiol-tethered RuII terpyridine complexes were synthesized for a voltage-driven molecular switch and used to understand the switch-on mechanism of the molecular switches of single metal complexes in the solid-state molecular junction in a vacuum. Electrochemical voltammetry and current-voltage (I-V) characteristics are measured to elucidate electron transport processes in the bistable conducting states of single molecular junctions of a molecular switch, Ru(II) terpyridine complexes. (1) On the basis of the Ru-centered electrochemical reaction data, the electron transport rate increases in the mixed self-assembled monolayer (SAM) of Ru(II) terpyridine complexes, indicating strong electronic coupling between the redox center and the substrate, along the molecules. (2) In a low-conducting state before switch-on, I-V characteristics are fitted to a direct tunneling model, and the estimated tunneling decay constant across the Ru(II) terpyridine complex is found to be smaller than that of alkanethiol. (3) The threshold voltages for the switch-on from low- to high-conducting states are identical, corresponding to the electron affinity of the molecules. (4) A high-conducting state after switch-on remains in the reverse voltage sweep, and a linear relationship of the current to the voltage is obtained. These results reveal electron transport paths via the redox centers of the Ru(II) terpyridine complexes, a molecular switch.

• 한국전기전자재료학회논문지
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• 제29권5호
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• pp.268-273
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• 2016

In this study, we observed current-voltage characteristics of the MIM (metal-insulator-metal) structure. The $WO_x$ material was used between metal electrodes as the oxide insulator. The structure of the $Al/WO_x/TiN$ shows bipolar resistive switching and the operating direction of the resistive switching is clockwise, which means set at negative voltage and reset at positive voltage. The set process from HRS (high resistance state) to LRS (low resistance state) occurred at -2.6V. The reset process from LRS to HRS occurred at 2.78V. The on/off current ratio was about 10 and resistive switching was performed for 5 cycles in the endurance characteristics. With consecutive switching cycles, the stable $V_{set}$ and $V_{reset}$ were observed. The electrical transport mechanism of the device was based on the migration of oxygen ions and the current-voltage curve is following (Ohm's Law ${\rightarrow}$ Trap-Controlled Space Charge Limited Current ${\rightarrow}$ Ohm's Law) process in the positive voltage region.