Nam-Yeal Lee

Electronics and Telecommunications Research Institute

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Sung‐Min Yoon

Electronics and Telecommunications Research Institute

Byoung‐Gon Yu

Electronics and Telecommunications Research Institute

Sang-Ouk Ryu

Dankook University

Kyu-Jeong Choi

Kyung Hee University

Seung-Yun Lee

Hanbat National University

Woong‐Chul Shin

Hyundai Pharm (South Korea)

Young‐Sam Park

Electronics and Telecommunications Research Institute

In‐Kyu You

Electronics and Telecommunications Research Institute

Seong M. Cho

Electronics and Telecommunications Research Institute

Kwi-Dong Kim

Electronics and Telecommunications Research Institute

Cooperative Institutions

Electronics and Telecommunications Research Institute

Government of the Republic of Korea

Daejeon University

Seoul National University

Korea Advanced Institute of Science and Technology

Chungnam National University

Yonsei University

Dong-Eui University

Pusan National University

Korea Atomic Energy Research Institute

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Phase Formations and Electrical Properties of Bi_3.15La_0.85Ti₃O₁₂ and Sm-Doped Bi_3.073La_0.85Sm_0.077Ti₃O₁₂ Thin Films with Annealing Temperature

Japanese Journal of Applied Physics (2004)

Sang-Ouk Ryu Nam-Yeal Lee Won–Jae Lee Soon‐Gil Yoon

The phase formation and electrical properties of (Bi,La) 4 Ti 3 O 12 (BLT) thin film and Sm-doped BLT thin films prepared by the chemical solution deposition method on Pt/Ti/SiO 2 /Si substrates have been investigated. It was observed that the microstructure and electrical properties of BLT thin films dramatically varied with Sm-doping and annealing temperature. The crystallinity and grain size in both types of BLT films were definitely increased with annealing temperatures of BLT films but these films exhibited slightly different crystallographic orientation, which resulted in the different remanent polarization in BLT films. The remanent polarization (2 P r ) of Sm-doped 130 nm-BLT films annealed at 750°C was about 26 µC/cm 2 . The Sm-doped BLT films also exhibited reduced leakage current density, compared to BLT films.

10.1143/jjap.43.6594

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Citations (4)

Phase Formations and Electrical Properties of Various (Bi, La)4Ti3O12 Thin Films by Chemical Solution Deposition

Journal of Electroceramics (2004)

Won–Jae Lee Ao Liu Byoungchul Shin Geun-Hyoung Lee Il‐Soo Kim

10.1007/s10832-004-5078-y

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Citations (0)

Excess Bismuth-Dependent Characteristics of Chemical Solution Deposited Bi_3.15La_0.85Ti₃O₁₂ Thin Films

Integrated ferroelectrics (2003)

Nam-Yeal Lee Won–Jae Lee Sang-Ouk Ryu In‐Kyu You Sung‐Min Yoon

The phase formation and electrical properties of (Bi3.15La0.85)Ti3O12 (BLT) thin films prepared by the chemical solution deposition method on Pt/Ti/SiO2/Si substrates have been investigated. It was observed that the microstructure and electrical properties of BLT thin films dramatically varied with the excess Bi content. The crystallographic orientation of BLT films was varied with excess Bi content and the intermediate rapid thermal annealing (RTA) process. While BLT thin films prepared without intermediate RTA process have ⟨117⟩ orientation irrespective of excess Bi content, BLT thin films with RTA process at 450°C have an orientation change with excess Bi content. The leakage current of BLT thin films slightly increased with increasing excess Bi content up to 6.5% and then considerably decreased in BLT film with 10% Bi, where was revealed to be almost stoichiometric composition.

Stoichiometry

Bismuth

10.1080/10584580390254501

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Citations (2)

Effect of ferroelectric switching time on fatigue behaviors of (117)- and (00l)-oriented (Bi,La)4Ti3O12 thin films

Thin Solid Films (2005)

Sung‐Min Yoon Nam-Yeal Lee Sang-Ouk Ryu Woong‐Chul Shin In‐Kyu You

Switching time

Ferroelectric capacitor

10.1016/j.tsf.2005.03.004

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Citations (9)

Etching Characteristics of $Ge_2Sb_2Te_5$ Using High-Density Helicon Plasma for the Nonvolatile Phase Change Memory Applications

Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference (2004)

Sung-Min Yoon Nam-Yeal Lee Sang-Ouk Ryu Woong-Chul Shln Byoung-Gon Yu

Helicon

Phase-change memory

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TIME DEPENDENT RESISTANCE CHANGE OF AMORPHOUS PHASE IN PHASE-CHANGE NONVOLATILE MEMORIES

Integrated ferroelectrics (2007)

Sung‐Min Yoon Kyu-Jeong Choi Nam-Yeal Lee Seung-Yun Lee Young‐Sam Park

ABSTRACT For the realization of reliable nonvolatile phase-change memory operations, it is very important to understand the long-term behaviors of memory states with different resistance values. We investigated the time-dependent behaviors of RESET resistance states (RR) for the fabricated memory devices using Sn-doped GST, in which Sn amounts were varied to control the initial values of RR. It was found that the transient variations of RR showed an increasing trend with time, and that their behaviors were closely related to the microstructure of amorphous phase in the phase-change material.

Phase-change memory

Non-Volatile Memory

Realization (probability)

Reset (finance)

10.1080/10584580701756151

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Citations (2)

Phase change memory device including a heating layer of a multi-layer structure

Seung-Yun Lee Byoung Gon Yu Nam-Yeal Lee Park Young Sam Yoon Sung Min

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Characterization of in situ diffusion of silver in Ge–Te amorphous films for programmable metallization cell memory applications

Journal of Vacuum Science & Technology B Microelectronics and Nanometer Structures Processing Measurement and Phenomena (2006)

Soojin Lee Soon‐Gil Yoon Kyu-Jeong Choi Sang-Ouk Ryu Sung‐Min Yoon

Silver-rich GeTe solid electrolytes for use in programmable metallization cell (PMC) memory devices were prepared by the in situ diffusion of silver into the GeTe films during the deposition of silver by rf sputtering on GeTe chalcogenide glass films. The concentration of silver in the silver-rich GeTe films was controlled by adjusting the concentration of Te in the GeTe films. A PMC memory device with a Ag(300nm)∕Agx(Ge45Te55)1−x(200nm)∕TiW(100nm) structure and a device diameter of 0.5μm showed reproducible memory characteristics based on resistive switching at low voltage with high Roff∕Ron ratios. The PMC memory device exhibited good switching characteristics up to 100cycles at an amplitude of ±2V and a pulse width of 1μs.

10.1116/1.2348884

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Citations (13)

Polycrystalline silicon-germanium heating layer for phase-change memory applications

Applied Physics Letters (2006)

Seung-Yun Lee Kyu-Jeong Choi Sang-Ouk Ryu Sung‐Min Yoon Nam-Yeal Lee

This letter reports on the performance improvement of phase-change memory (PCM) cells by applying silicon-germanium (SiGe) alloys as resistive heating layers. The in situ doped polycrystalline Si0.75Ge0.25 films, lying under holes filled with a Ge2Sb2Te5 (GST) phase-change material in a pore-style configuration, promoted the temperature rise and phase transition in the GST. The SiGe heating layer caused drastic reduction in both set and reset currents compared to a conventional TiN heater material. The threshold voltages of the PCM cells were almost uniform irrespective of the kind of heating layers. It is considered that this beneficial effect of the SiGe heating layer originates from the high electrical resistivity and low thermal conductivity of a SiGe alloy.

Polycrystalline silicon

Phase-change memory

10.1063/1.2335363

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Citations (50)

Nitrogen Incorporation on the Crystallization Temperature of Silver-Doped Ge[sub 45]Te[sub 55] Solid-Electrolyte Films for PMC Memory Applications

Electrochemical and Solid-State Letters (2006)

Soojin Lee Soon‐Gil Yoon Kyu-Jeong Choi Sang-Ouk Ryu Sung‐Min Yoon

A programmable metallization cell (PMC) memory structure with silver-saturated solid-electrolyte films doped by nitrogen was prepared on a bottom electrode by a cosputtering technique at room temperature. The solid-electrolyte films deposited with various flow ratios showed an increase of crystallization temperature and especially, the electrolyte films deposited at ratios above 30% showed a crystallization temperature above 400°C, resulting in survival of a back-end process in semiconductor memory devices. A PMC memory device with nitrogen-doped solid electrolytes shows reproducible memory characteristics based on resistive switching at threshold voltage of with high ratios.

Fast ion conductor

10.1149/1.2360017

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Citations (6)