• Proceedings of the Korean Magnestics Society Conference
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• 2000.09a
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• pp.33-59
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• 2000

Demonstrated uniform MR and resistance across 6 inch wafer, Demonstrated successful integration of MTJ and CMOS, Measured address access time of 8ns and read cycle time of 18ns for 256${\times}$2 arrays at 3.0V using a single transistor and MTJ for a cell

• Proceedings of the Korean Information Science Society Conference
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• 2006.10a
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• pp.261-266
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• 2006

최근 낸드 플래시 메모리는 임베디드 저장 장치로서 많이 사용되고 있을 뿐만 아니라 플래시 메모리의 저장 용량의 대용량화로 하드 디스크를 대체하는 SSD(solid state disk) 같은 제품이 출시되고 있다. 플래시 메모리는 하드디스크에 비하여 저전력, 빠른 접근성, 물리적 안정성 등의 장점이 있지만 읽기와 쓰기의 연산의 불균형적인 비용과 덮어 쓰기가 안 되고 쓰기 전에 해당 블록을 지워야하는 부가적인 작업을 수행해야 한다. 이와 같은 특징은 플래시 메모리의 쓰기 성능을 저하 시키고 기존의 하드디스크를 대체하는 것을 어렵게 만든다. 이와 같은 플래시 메모리의 단점을 해결하기 위해서 본 논문에서 비휘발성 메모리와 플래시 메모리를 함께 사용하는 방법을 제안한다. 최근 MRAM, FeRAM, PRAM과 같은 차세대 메모리 기술의 발전과 배터리 백업 메모리의 가격 하락으로 인하여 비휘발성 메모리의 상품적 가치가 높아지고 있다. 하지만 아직까지 용량 대비 가격이 비효율적이기 때문에 소용량의 비휘발성 메모리를 활용하여 플래시 메모리의 쓰기 연산에 대한 단점을 보완하는 방법을 제안한다. 본 논문에서는 FTL 에서 비휘발성 메모리를 쓰기 버퍼로 이용한 여러 가지 버퍼 관리 정책을 실험하였고 각 관리 정책에 따른 플래시 메모리의 성능 향상을 측정하였다. 실험을 통하여 최대로 읽기의 횟수는 90% 감소, 쓰기 횟수는 33% 감소, 소거 횟수는 50% 감소 효과를 보였다.

• Smart Media Journal
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• v.8 no.1
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• pp.19-26
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• 2019

At the opening ceremony of 2018 Winter Olympics in PyeongChang, an unknown cyber-attack occurred. The malicious code used in the attack is based on in-memory malware, which differs from other malicious code in its concealed location and is spreading rapidly to be found in more than 140 banks, telecommunications and government agencies. In-memory malware accounts for more than 15% of all malicious codes, and it does not store its own information in a non-volatile storage device such as a disk but resides in a RAM, a volatile storage device and penetrates into well-known processes (explorer.exe, iexplore.exe, javaw.exe). Such characteristics make it difficult to analyze it. The most recently released in-memory malicious code bypasses the endpoint protection and detection tools and hides from the user recognition. In this paper, we propose a method to efficiently extract the payload by unpacking injection through IDA Pro debugger for Dorkbot and Erger, which are in-memory malicious codes.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2006.10a
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• pp.166-169
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• 2006

A promising capacitor, which has conformable step coverage and good uniformity of thickness and composition, is needed to manufacture high-density non-volatile FeRAM capacitors with a stacked cell structure. In this study, ferroelectric $Bi_{3.61}Nd_{0.39}Ti_3O_{12}$ (BNT) thin films were prepared on $Pt(111)/Ti/SiO_2/Si$ substrates by the liquid delivery system MOCVD method. In these experiments, $Bi(ph)_3$, $Nd(TMHD)_3$ and $Ti(O^iPr)_2(TMHD)_2$ were used as the precursors and were dissolved in n-butyl acetate. The BNT thin films were deposited at a substrate temperature and reactor pressure of approximately $600^{\circ}C$ and 4.8 Torr, respectively. The microstructure of the layered perovskite phase was observed by XRD and SEM. The remanent polarization value (2Pr) of the BNT thin film was $31.67\;{\mu}C/cm^2$ at an applied voltage of 5 V.

• JSTS:Journal of Semiconductor Technology and Science
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• v.8 no.1
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• pp.80-84
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• 2008

We systematically investigated the resistive switching properties of thin $TiO_2$ films on Pt/Ti/$SiO_2$/Si substrates that were embedded with a Co ultra thin layer. An in-situ sputtering technique was used to grow both films without breaking the chamber vacuum. A stable bipolar switching in the current-voltage curve was clearly observed in $TiO_2$ films with an embedded Co ultra thin layer, addressing the high and low resistive state under a bias voltage sweep. We propose that the underlying origin involved in the bipolar switching may be attributed to the interface redox reaction between the Co and $TiO_2$ layers. The improved reproducible switching properties of our novel structures under forward and reverse bias stresses demonstrated the possibility of future non-volatile memory elements in a simple capacitive-like structure.

• 한국신재생에너지학회:학술대회논문집
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• 2011.11a
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• pp.122.1-122.1
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• 2011

The motivation for this work was the potential of hydrophobic amino acids such as glycine, L-alanine, and L-valine to be applied as thermodynamic hydrate inhibitors (THIs). To confirm their capabilities in inhibiting the formation of gas hydrates, three-phase (liquid-hydrate-vapor) equilibrium conditions for carbon dioxide hydrate formation in the presence of 0.1 to 3.0 mol% amino acid solutions were determined in the range of 273.05 to 281.45 K and 14.1 to 35.2 bar. From quantitative analyses, the inhibiting effects of the amino acids (on a mole concentration basis) decreased in the following order: L-valine > L-alanine > glycine. The application of amino acids as THIs has several potential advantages over conventional methods. First, the environmentally friendly nature of amino acids as compared to conventional inhibitors means that damage to ecological systems and the environment could be minimized. Second, the loss of amino acids in recovery process would be considerably reduced because amino acids are non-volatile. Third, amino acids have great potential as a model system in which to investigate the inhibition mechanism on the molecular level, since the structure and chemical properties of amino acids are well understood.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.37 no.4
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• pp.7-14
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• 2000

A Bi$_{4}$Ti$_{3}$O$_{12}$ (BIT) thin film is prepared by sol-gel method using acetate precursors and evaluated whether it could be applied to NVFRAM (Non-Volatile Ferroelectric RAM). The drying and the annealing temperature are 40$0^{\circ}C$ and $650^{\circ}C$, respectively and they are determined from the DT-TG (Differential Thermal-Thermal Gravimetric) analysis. The BIT thin film deposited on Pt/Ta/SiO$_{2}$/Si substrate shows orthorhombic perovskite phase. The grain size and the surface roughness are about 100 nm and 70.2$\AA$, respectively. The dielectric constant and the loss tangent at 10 KHz are 176 and 0.038, respectively, and the leakage current density at 100 ㎸/cm is 4.71 $mutextrm{A}$/$\textrm{cm}^2$. In the results of hysteresis loops measured at $\pm$250 ㎸/cm, the remanent polarization (Pt) and the coercive field (Ec) are 5.92 $\mu$C/$\textrm{cm}^2$ and 86.3 ㎸/cm, respectively. After applying 10$^{9}$ square pulses of $\pm$5V, the remanent polarization of the BIT thin film decreases as much as about 33% from 5.92 $\mu$C/$\textrm{cm}^2$ of initial state to 3.95 $\mu$C/$\textrm{cm}^2$.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.38 no.1
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• pp.26-45
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• 2001

The Flash memory market: is an exciting market that has quickly over the last 10 years. Recently Flash memory provides a high-density. truly non-volatile, high performance read write memory solutions, also is characterized by low power consumption, extreme ruggedness and high reliability. Flash memory is an optimum solution for large nonvolitilc storage operations such as solid file storage, digital video recorder, digital still camera, The MP3 player and other portable multimedia communication applications requiring non-volatility. Regardless of the type of Flash memory, Flash media management software is always required to manage the larger Flash memory block partitions. This is true, since Flash memory cannot be erased on the byte level common to memory, but must be erased on a block granularity. The management of a Flash memory manager requires a keen understanding of a Flash technology and data management methods. Though Flash memory's write performance is relatively slow, the suggested algorithm offers a higher maximum write performance. Algorithms so far developed is not suitable for applications which is requiring more fast and frequent accesses. But, the proposed algorithm is focused on the justifiable operation even in the circumstance of fast and frequent accesses.

• JSTS:Journal of Semiconductor Technology and Science
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• v.11 no.3
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• pp.146-152
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• 2011

Thermal stability of $Ge_2Sb_2Te_5$ (GST) and $SiO_2$ doped GST (SGST) films for phase change random access memory applications was investigated by observing the change of surface roughness, layer density and composition of both films after isothermal annealing. After both GST and SGST films were annealed at $325^{\circ}C$ for 20 min, root mean square (RMS) surface roughness of GST was increased from 1.9 to 35.9 nm but that of SGST was almost unchanged. Layer density of GST also steeply decreased from 72.48 to 68.98 $g/cm^2$ and composition was largely varied from Ge : Sb : Te = 22.3 : 22.1 : 55.6 to 24.2 : 22.7 : 53.1, while those of SGST were almost unchanged. It was confirmed that the addition of a small amount of $SiO_2$ into GST film restricted the deterioration of physical and chemical properties of GST film, resulting in the better thermal stability after isothermal annealing.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.5
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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.