• Journal of the Korean Magnetics Society
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• v.22 no.5
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• pp.162-166
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• 2012

V-I characteristics of Fe(100)/MgO(100)/Cu-phthalocyanine (CuPc)/Co hybrid magnetic tunnel junctions were investigated at different temperatures. Fe(100) and Co ferromagnetic layers were separated by an organic-inorganic hybrid barrier consisting of different thickness of CuPc thin film grown on a 2 nm thick epitaxial MgO(100) layer. As the CuPc thickness increases from 0 to 10 nm, a bistable switching behavior due to strong charging effects was observed, while a very large magenetoresistance was shown at 77 K for the junctions without the CuPc barrier. This switching behavior decreases with the increase in temperature, and finally disappears beyond 240 K. In this work, high-potential future applications of the MgO(100)/CuPc bilayer were discussed for hybrid spintronic devices as well as polymer random access memories (PoRAMs).

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.10a
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• pp.15.2-15.2
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• 2011

비휘발성 저항 메모리소자인 resistance random access memory (ReRAM)는 간단한 소자구조와 빠른 동작특성을 나타내며 고집적화에 유리하기 때문에 차세대 메모리소자로써 각광받고 있다. 현재, 이성분계 산화물, 페로브스카이트 산화물, 고체 전해질 물질, 유기재료 등을 응용한 저항 메모리소자에 대한 연구가 활발히 진행되고 있다. 그 중 ZnO를 기반으로 하는 amorphous InGaZnO (a-IGZO) 박막은 active layer 로써 박막트랜지스터 적용 시 우수한 전기적 특성을 나타내며, 빠른 동작특성과 높은 저항 변화율을 보이기 때문에 ReRAM 에 응용 가능한 재료로써 기대되고 있다. 또한 가시광선 영역에서 광학적으로 투명한 특성을 보이기 때문에 투명소자로서도 응용이 기대되고 있다. 본 연구에서는 indium tin oxide (ITO) 투명 전극을 적용한 ITO/a-IGZO/ITO 구조의 투명 소자를 제작하여 저항 메모리 특성을 평가하였다. Radio frequency (RF) sputter를 이용하여 IGZO 박막을 합성하고, ITO 전극을 증착하여 투명 저항 메모리소자를 구현하였고, resistive switching 효과를 관찰하였다. 또한, 열처리를 통해 a-IGZO 박막 내의 Oxygen vacancy와 같은 결함의 정도에 따른 on/off 저항의 변화를 관찰할 수 있었다. 제작된 저항 메모리소자는 unipolar resistive switching 특성을 보였으며, 높은 on/off 저항의 차이를 유지하였다. Scanning electron microscope (SEM)을 통해 합성된 박막의 형태를 평가하였고, X-ray diffraction (XRD) 및 transmission electron microscopy (TEM)을 통해 결정성을 평가하였다. 제작된 소자의 전기적 특성은 HP-4145 를 이용하여 측정하고 비교 분석하였다.

• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.78.1-78.1
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• 2012

비 휘발성 저항 메모리소자인 resistance random access memory (ReRAM)는 빠른 동작특성과 저 전압 특성을 나타내고 비교적 간단한 소자구조로 고집적화에 유리하여 기존의 DRAM과 flash 메모리, SRAM 등이 갖고 있는 한계를 극복할 수 있는 차세대 메모리소자로써 각광받고 있다. 현재, 이성분계 산화물, 페로브스카이트 산화물, 고체 전해질 물질, 유기재료 등을 응용한 저항 메모리소자에 대한 연구가 활발히 진행되고 있다. 그 중 ZnO 를 기반으로 하는 amorphous InGaZnO (a-IGZO) 박막은 저온에서 대면적 증착이 가능하며 다른 비정질 재료에 비해 높은 전하 이동도를 갖기 때문에 박막트랜지스터 적용 시 우수한 전기적 특성을 나타낸다. 또한 빠른 동작특성과 높은 저항 변화율을 보이기 때문에 ReRAM에 응용 가능한 재료로써 기대되고 있다. 본 연구에서는 MOM(metal/oxide/metal) 구조를 기반한 TiN/a-IGZO/ITO 구조의 소자를 제작하여 저항 메모리 특성을 평가하였다. IGZO 박막은 radio frequency (RF) sputter 를 이용하여 ITO/glass 기판 위에 증착하였다. MOM 구조를 위한 상부 TiN 전극은 e-beam evaporation 을 이용하여 증착하였다. 제작된 저항 메모리소자는 안정적인 unipolar resistive switching 특성을 나타내었으며, TiN 상부전극과 IGZO 계면 간의 Transmission Electron Microscopy (TEM) 분석을 통해 전압 인가 후 전극 금속 물질의 박막 내 삽입으로 인한 금속 필라멘트의 형성을 관찰 할 수 있었다. 합성된 박막의 형태와 결정성은 Scanning electron microscope (SEM)와 X-ray Diffraction (XRD)을 통해 평가 하였으며, 제작된 소자의 전기적 특성은 HP-4145 를 이용하여 측정하고 비교 분석하였다.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.6
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• pp.799-803
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• 2018

We demonstrated memory thin-film transistors (MTFTs) with organic ferroelectric polymer poly(vinylidene fluoride-co-trifluoroethylene) and an amorphous oxide semiconducting indium gallium zinc oxide channel on the elastomeric substrate. The dielectric constant for the P(VDF-TrFE) thin film prepared on the elastomeric substrate was calculated to be 10 at a high frequency of 1 MHz. The voltage-dependent capacitance variations showed typical butterfly-shaped hysteresis behaviors owing to the polarization reversal in the film. The carrier mobility and memory on/off ratio of the MTFTs showed $15cm^2V^{-1}s^{-1}$ and $10^6$, respectively. This result indicates that the P(VDF-TrFE) film prepared on the elastomeric substrate exhibits ferroelectric natures. The fabricated MTFTs exhibited sufficiently encouraging device characteristics even on the elastomeric substrate to realize mechanically stretchable nonvolatile memory devices.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.3
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• pp.2131-2134
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• 2015

In this study, It has been demonstrated a new and realizable possibility of the ferroelectric random access memory devices by all solution processing method with paper substrates. Organic ferroelectric poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) thin films were formed on paper substrate with Al electrode for the bottom gate structure using spin-coating technique. Then, they were subjected to annealing process for crystallization. The fabricated PVDF-TrFE thin films were observed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). It was found from polarization versus electric field (P-E) measurement that a PVDF-TrFE thin film on paper substrate showed very good ferroelectric property. This result agree well with that of a PVDF-TrFE thin film fabricated on the rigid Si substrate. It anticipated that these results will lead to the emergence of printable electron devices on paper. Furthermore, it could be fabricated by a solution processing method for ferroelectric random access memory device, which is reliable and very inexpensive, has a high density, and can be also fabricated easily.

• Journal of Adhesion and Interface
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• v.22 no.4
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• pp.144-152
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• 2021

Understanding charge transfer across the interface between organic semiconductor and gate insulator gives insight into the development of high-performance organic memory as well as highly stable organic field-effect transistors (OFETs). In this work, we firstly unveil a novel interfacial charge transfer mechanism, in which hole transfer from organic semiconductor to polymer insulator was nonlinearly boosted by localized states coupling. For this, OFETs based on rubrene single crystal semiconductor and Mylar gate insulator were fabricated via vacuum lamination, which allows stable repetition of lamination and delamination between semiconductor and gate insulator. The surfaces of rubrene single crystal and Mylar film were selectively degraded by photo-induced oxygen diffusion and UV-ozone treatment, respectively. Consequently, we found that the interfacial charge transfer and resultant bias-stress effect were nonlinearly boosted by coupling between localized states in rubrene and Mylar. In particular, the small number of localized states in rubrene single crystal provided fluent pathway for interfacial charge transport.

• Journal of Advanced Navigation Technology
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• v.18 no.2
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• pp.178-184
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• 2014

CMOS technology based on PCA is very efficient at an implementation of memory or ALU. However, there has been a growing interest in quantum-dot cellular automata (QCA) because of the limitation of CMOS scaling. In this paper, we propose a design of PCA architecture based on QCA. In the proposed PCA design, we utilize D flip-flop and XOR logic gate without wire crossing technique, and design a input and rule control switches. In experiment, we perform the simulation of the proposed PCA architecture by QCADesigner. As the result, we confirm the efficiency the proposed architecture.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.8 no.3
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• pp.411-418
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• 1998

The thickness dependence of stress electric filed oxide currents has been measured in oxides with thicknesses between 10 nm and 80 nm. The oxide currents were shown to be composed of stress current and transient current. The stress current was composed of stress induced leakage current and dc current. The stress current was caused by trap assisted tunneling through the oxide. The transient current was caused by the tunneling charging and discharging of the trap in the interfaces. The stress current was used to estimate to the limitations on oxide thicknesses. The transient current was used to the data retention in memory devices.

• Applied Chemistry for Engineering
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• v.24 no.3
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• pp.219-226
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• 2013

Organic semiconductor-based soft electronics has potential advantages for next-generation electronics and displays, which request mobile convenience, flexibility, light-weight, large area, etc. Organic field-effect transistors (OFET) are core elements for soft electronic applications, such as e-paper, e-book, smart card, RFID tag, photovoltaics, portable computer, sensor, memory, etc. An optimal multi-layered structure of organic semiconductor, insulator, and electrodes is required to achieve high-performance OFET. Since most organic semiconductors are self-assembled structures with weak van der Waals forces during film formation, their crystalline structures and orientation are significantly affected by environmental conditions, specifically, substrate properties of surface energy and roughness, changing the corresponding OFET. Organo-compatible insulators and surface treatments can induce the crystal structure and orientation of solution- or vacuum-processable organic semiconductors preferential to the charge-carrier transport in OFET.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.95-96
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• 2006

CMOS Image Sensor(CIS) 소자에서 광감도의 향상과 천연색 형성을 위하여 적용하고 있는 Color-Filter 공정에서 국부적으로 발생하는 strip성 불량과 막질손상을 제거하기 위한 연구를 진행하였다. 우선 지역적 경향성을 보이는 불량에 대해서는 PR strip process type을 액조 진행방식에서 회전식으로 변경했을 때 제거됨을 확인하였고, 막질손상을 최소화하기 위해서는 새로운 유기용매의 적용이 필요하였다. 실험 결과, 케톤기를 가지는 화합물과 Polar Apotic 용매의 혼합화합물을 적용하였을 때 각 막질에 attack을 최소화하면서 원하는 PR만 선택적으로 제거 되며 미세잔류성분에 대한 제거력도 향상됨을 확인하였다.