• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.103-104
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• 2006

PRAM (Phase change Random Access Memory) is one of the most promising candidates for next generation Non-volatile Memories. The Phase change material has been researched in the field of optical data storage media. However, the characteristics required in solid state memory are quite different from optical ones. In this study, the reset current and temperature profile of PRAM cells with bottom electrode were calculated by the numerical method.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.69-70
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• 2006

A detailed Investigation of cell structure and electrical characteristic in chalcogenide-based phase-change random access memory(PRAM) devices is presented. We used compound of Ge-Sb-Te material for phase-change cell. A novel bottom electrode structure and manufacture are described. We used heat radiator structure for improved reset characteristic. A resistance change measurement is performed on the test chip. From the resistance change, we could observe faster reset characteristic.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.347-347
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• 2010

In other to progress better crystallization transition and long phase-transformation data of phase-change memory (PRAM), we investigated about the effect of Sb doping and Ag ions percolating into Ge-Se-Te phase-change material. Doped Sb concentrations was determined each of 10 wt%, 20 wt% and 30 wt%. As the Sb-doping concentration was increased, the resistivity decreased and the crystallization temperature increased. Ionization of Ag was progressed by DPSS laser (532 nm) for 1 hour. The resistivity was more decreased and the crystallization temperature was more increased in case of adding Ag layer under Sb-(Ge-Se-Te) thin film. At the every condition of thin films included Ag layer more stable states were indicated compare with just Sb-doped Ge-Se-Te thin films.

• Journal of applied mathematics & informatics
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• v.5 no.2
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• pp.427-432
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• 1998

When an undirected tree T and a vertex ${\gamma}$ in the tree are given the problem to transform T into a rooted tree with ${\gamma}$ as its root is considered. Using Euler tour and prefix sum an optimal algorithm has been developed [2,3]. We will present another parallel algorithm which is optimal also on EREW PRAM. Our approach resuces the given tree step by step by pruning and pointer jumping. That is the tree structure is retained during algorithm processing such that than other tree computations can be carried out in parallel.

• Journal of the Korean Ceramic Society
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• v.42 no.5 s.276
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• pp.326-332
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• 2005

Phase transformation effects on mechanical properties of $Ge_2Sb_2Te_5$, which is a promising candidate material for Phase Change Random Access Memory (PRAM), were studied. $Ge_2Sb_2Te_5$ thin films, which was thermally annealed with different conditions, were analyzed using XRD, AFM, 4-point probe method and reflectance measurement. As the temperature and the dwelling time increased, crystallity and grain size increased, which enhanced elastic modulus and hardness. Furthermore, N2 doping, which was used for better electrical properties, was proved to decrease elastic modulus and hardness of $Ge_2Sb_2Te_5$.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1287-1288
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• 2008

In the past work, we showed that $Ge_1Se_1Te_2$ thin films provide a promising alternative for PRAM applications to overcome the problems of conventional $Ge_2Sb_2Te_5$ PRAM devices. However, $Ge_1Se_1Te_2$ thin films were unstable at SET and RESET process. Because of unstable state and its melting temperature, we alloyed As for 5wt%, 10wt% and 15wt% respectively. The phase transition temperature of $Ge_1Se_1Te_2$-only thin film is found to be 213$^{\circ}C$ while As 10wt% alloyed $Ge_1Se_1Te_2$ showed phase transition at 242$^{\circ}C$ with more stability.

• Journal of applied mathematics & informatics
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• v.12 no.1_2
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• pp.21-29
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• 2003

Let G be a graph with n vertices and n edges. The problem of constructing a spanning tree is to find a connected subgraph of G with n vertices and n -1 edges. In this paper, we propose an O(log n) time parallel algorithm with O(n/ log n) processors on an EREW PRAM for constructing a spanning tree on trapezoid graphs.

• Journal of KIISE:Computer Systems and Theory
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• v.33 no.12
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• pp.880-884
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• 2006

In an edge-weighted(positive, negative, or zero weights are possible) tree, we want to solve the problem of finding a longest path such that the sum of the weights of the edges in tile path is non-negative. To find a longest non-negative path of a tree we present a sequential algorithm with O(n logn) time and a CREW PRAM parallel algorithm with $O(log^2n)$ time and O(n) processors. where n is the number of nodes in the tree.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2009.05a
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• pp.110-110
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• 2009

최근 차세대 비휘발성 메모리(NVM) 기술은 메모리의 성능과 기존의 한계점을 효과적으로 극복하며 활발한 연구를 통해 비약적으로 발전하고 있으며 특히, phase-change random access memory (PRAM)은 ferroelectric random access memory (FeRAM)과 magneto-resistive random access memory (MRAM)과 같은 다른 NVM 소자와 비교하여 기존의 DRAM과 구조적으로 비슷하고 상용화가 빠르게 진행될 수 있을 것으로 예상되는 바, PRAM에 사용되는 상변화 물질의 식각을 수행하고 X-ray photoelectron spectroscopy (XPS)를 통해 표면의 열화현상을 관찰하였다.

• Journal of KIISE:Computer Systems and Theory
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• v.33 no.7
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• pp.448-453
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• 2006

We extend a parallel depth-first search (DFS) algorithm for planar graphs to deal with (non-planar) solid grid graphs, a subclass of non-planar grid graphs. The proposed algorithm takes time O(log n) with $O(n/sqrt{log\;n})$ processors in Priority PRAM model. In our knowledge, this is the first deterministic NC algorithm for a non-planar graph class.