35 results on '"Sijung Yoo"'
Search Results
2. Drain Current Degradation Induced by Charge Trapping/De-Trapping in Fe-FET.
- Author
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Taeyoung Kim, Suhwan Lim, Ilho Myeong, Sanghyun Park, Suseong Noh, Seung Min Lee, Jongho Woo, Hanseung Ko, Youngji Noh, Moonkang Choi, Kiheun Lee, Sangwoo Han, Jongyeon Baek, Kijoon Kim, Dongjin Jung, Jisung Kim, Jaewoo Park, Seunghyun Kim, Hyoseok Kim, Sijung Yoo, Hyun Jae Lee, Duk-Hyun Choe, Seung-Geol Nam, Ilyoung Yoon, Chaeho Kim, Kwanzsoo Kim, Kwanzmin Park, Bong Jin Kuh, Jinseong Heo, Wanki Kim, Daewon Ha, and Jaihyuk Song
- Published
- 2024
- Full Text
- View/download PDF
3. Structural and Device Considerations for Vertical Cross Point Memory with Single-stack Memory toward CXL Memory beyond 1x nm 3DXP.
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Sijung Yoo, Donghoon Kim, Yoon Mo Koo, Sujee Kim Wooju Jeong, Hyungjoon Shim, Won-Jun Lee, Beom Seok Lee, Seungyun Lee, Hyejung Choi, Hyung Dong Lee, Taehoon Kim, and Myung-Hee Na
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- 2022
- Full Text
- View/download PDF
4. PE-ALD of Ge1−xSxamorphous chalcogenide alloys for OTS applications
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Seung-Min Chung, Hyung Keun Kim, Taeyoon Lee, Minkyu Lee, Seok Man Hong, Sijung Yoo, Myoungsub Kim, Youngjun Kim, Tae-Hoon Kim, and Hyungjun Kim
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010302 applied physics ,Materials science ,Chalcogenide ,business.industry ,Band gap ,02 engineering and technology ,General Chemistry ,Plasma ,021001 nanoscience & nanotechnology ,01 natural sciences ,Threshold voltage ,Amorphous solid ,Atomic layer deposition ,chemistry.chemical_compound ,chemistry ,0103 physical sciences ,Materials Chemistry ,Optoelectronics ,Thin film ,0210 nano-technology ,business ,Scaling - Abstract
Three-dimensional (3D) cross-point (X-point) technology, including amorphous chalcogenide-based ovonic threshold switching (OTS) selectors, is bringing new changes to the memory hierarchy for high-performance computing systems. To prepare for future 3D X-point memory scaling, we studied the plasma-enhanced atomic layer deposition (PE-ALD) of Ge1−xSx amorphous chalcogenide alloy thin films, the selection of which was motivated by their high optical bandgap and wide amorphous forming regions. The PE-ALD Ge1−xSx thin films were synthesized using a GeCl4 precursor and H2S plasma reactant, and their self-limited growth characteristics were studied in detail as a function of the exposure time of the ALD steps, temperature, and plasma power. The PE-ALD GeS2 thin film showed an RMS roughness of 0.29 nm and good conformality in the vertical 3D structure. Moreover, the OTS behavior of GeS2 and Ge2S3 mushroom-type devices with a 50 nm bottom electrode contact (BEC) were investigated as well as the trade-off relationship between the threshold voltage (1.9–6.2 V) and the normalized off current (20–250 nA) based on scaling the film thickness down from 30 nm to 5 nm. In particular, the GeS2 device showed a higher threshold field (∼3.1 MV cm−1) and lower normalized off current characteristics than the Ge2S3 device due to the higher trap density (2.1 × 1021 cm−3), according to the modified Poole–Frenkel (PF) model. The results achieved by this PE-ALD research on this novel binary GeS2 amorphous chalcogenide for OTS applications will contribute to the development of future 3D cross-point memory scaling.
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- 2021
5. Electro-Thermal Model for Thermal Disturbance in Cross-Point Phase-Change Memory
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Hyejung Choi, Seungyun Lee, Hyung Dong Lee, Sijung Yoo, and Tae-Hoon Kim
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010302 applied physics ,Materials science ,Nucleation ,Dielectric ,01 natural sciences ,Molecular physics ,Electronic, Optical and Magnetic Materials ,law.invention ,Phase-change memory ,Temperature gradient ,Thermal conductivity ,law ,0103 physical sciences ,Thermal ,Electrical and Electronic Engineering ,Crystallization ,Pulse-width modulation - Abstract
We developed an electro-thermal model for cross-point phase-change memory (X-PCM) and compared the calculation values with the experimental results. In order to simulate the electro-thermal phenomenon such as thermal disturbance (TDB) of victim cells and reset the current ( ${I}_{{\text {RESET}}}$ ) of aggressor cells in a fully confined cross-point structure, a three by three mini-array was constructed with the finite-elemental method. Unlike the conventional thermal model, which only shows the temperature gradient for TDB, our new model can predict the crystallization behavior of victim cells by combining the crystallization model for nucleation and growth. This makes it possible to compare the calculation results with the experimental ones through the crystalline fraction of the victim cell. The simulation results clearly reveal that our new model can closely estimate the victim cell’s crystalline fraction for TDB, with the variation of both pulse height (PH) and pulse width (PW) during the RESET operation. Applying the confirmed model for devices of smaller dimensions shows that TDB increases as the device scales down. The increase of TDB is particularly severe as cells become smaller than 16 nm. We suggest that TDB can be reduced not only by decreasing the thermal conductivity ( $\kappa $ ) of the interlayer dielectric (ILD), but also by minimizing the PW of the aggressor.
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- 2020
6. Understanding the Coexistence of Two Bipolar Resistive Switching Modes with Opposite Polarity in Pt/TiO2/Ti/Pt Nanosized ReRAM Devices
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Felix Cüppers, Rainer Waser, Sijung Yoo, Cheol Seong Hwang, Carsten Funck, Dirk J. Wouters, Stephan Menzel, Susanne Hoffmann-Eifert, and Hehe Zhang
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010302 applied physics ,Resistive touchscreen ,Materials science ,Polarity (physics) ,business.industry ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Resistive random-access memory ,symbols.namesake ,Resistive switching ,0103 physical sciences ,symbols ,Optoelectronics ,General Materials Science ,0210 nano-technology ,business ,Random access ,Quantum tunnelling ,Von Neumann architecture - Abstract
Redox-type resistive random access memories based on transition-metal oxides are studied as adjustable two-terminal devices for integrated network applications beyond von Neumann computing. The pre...
- Published
- 2018
7. Chemical interactions in the atomic layer deposition of Ge–Sb–Se–Te films and their ovonic threshold switching behavior
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Yoon Kyeung Lee, Sijung Yoo, Chanyoung Yoo, Cheol Seong Hwang, Eui-Sang Park, and Woohyun Kim
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Materials science ,business.industry ,02 engineering and technology ,General Chemistry ,Chemical interaction ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Amorphous solid ,Atomic layer deposition ,Materials Chemistry ,Optoelectronics ,0210 nano-technology ,business ,Stoichiometry - Abstract
Ge–Sb–Se–Te (GSST) quaternary films were prepared through atomic layer deposition (ALD) to ensure their amorphous stability for ovonic threshold switching (OTS) applications. Se, a typical phase-change material, was incorporated into Ge–Sb–Te (GST) films using Sb (OC2H5)3 and [(CH3)3Si]2Se precursors. The process produces highly conformal, uniform films consisting of stoichiometric binaries of GeTe2, Sb2Te3, and Sb2Se3. A detailed analysis of the atomic compositions revealed Te substitution for Se on the film surface through the ligand exchange reaction between the Te and Se precursors. Comparative experimental and simulation studies on the OTS behaviors showed that Ge and Se increase the optical bandgaps while Se decreases the density of the localized states. The amorphous stability of the Se-containing films enhances the cycling endurance of the OTS device up to 105 cycles. As conformality and atomic-level accuracy in terms of thickness and composition are prerequisites for three-dimensional crossbar-type passive arrays, the ALD process and the OTS performance presented in this work have a high potential utility for constructing a selector element in non-volatile high-density memories.
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- 2018
8. Atomic Layer Deposition of GeTe and Ge–Sb–Te Films Using HGeCl3, Sb(OC2H5)3, and {(CH3)3Si}2Te and Their Reaction Mechanisms
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Cheol Seong Hwang, Chanyoung Yoo, Sergei A. Ivanov, Sang Gyun Kim, Taehong Gwon, Eui-Sang Park, Taeyong Eom, Moo-Sung Kim, Manchao Xiao, Sijung Yoo, and Iain Buchanan
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Reaction mechanism ,Materials science ,General Chemical Engineering ,02 engineering and technology ,General Chemistry ,Substrate (electronics) ,GeSbTe ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Phase-change memory ,chemistry.chemical_compound ,Crystallography ,Atomic layer deposition ,chemistry ,Materials Chemistry ,Thin film ,0210 nano-technology ,Ternary operation ,Stoichiometry - Abstract
In this paper, a new atomic layer deposition (ALD) process for depositing binary GeTe and ternary Ge–Sb–Te thin films is reported, where HGeCl3 and ((CH3)3Si)2Te were used as Ge and Te precursors, respectively. The precursors reacted together to form the films at a low substrate temperature of 50–100 °C, without involving any additional reactive process gas. HCl elimination from the Ge precursor to form the divalent Ge intermediate, GeCl2, is proposed to explain the formation of 1:1 composition stoichiometric GeTe films. The GeTe films are promising for use in phase change memory applications. Ternary Ge–Sb–Te films were deposited by combining the GeTe ALD process with a previously developed ALD process for Sb2Te3 films, where Sb(OC2H5)3 and ((CH3)3Si)2Te were employed respectively as the Sb and Te precursors. However, the composition of the ternary GeSbTe films deviated slightly from the desired GeTe–Sb2Te3 pseudobinary composition suggesting that a certain unwanted reaction was involved between the prev...
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- 2017
9. Atomic Layer Deposition of GeTe Films Using Ge{N[Si(CH3)3]2}2, {(CH3)3Si}2Te, and Methanol
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Sijung Yoo, Manchao Xiao, Sergei Vladimirovich Ivanov, Deok-Yong Cho, Iain Buchanan, Cheol Seong Hwang, Taehong Gwon, Taeyong Eom, Moo-Sung Kim, and Han-Koo Lee
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Materials science ,Hydrogen ,020209 energy ,General Chemical Engineering ,Analytical chemistry ,chemistry.chemical_element ,02 engineering and technology ,General Chemistry ,Chemical reaction ,chemistry.chemical_compound ,Crystallography ,Atomic layer deposition ,chemistry ,Oxidation state ,0202 electrical engineering, electronic engineering, information engineering ,Materials Chemistry ,Wafer ,Reactivity (chemistry) ,Methanol ,Thin film - Abstract
In this report, a new method to deposit GeTe thin film by atomic layer deposition (ALD) is described. Ge(N(Si(CH3)3)2)2, in which Ge is in +2 oxidation state, and ((CH3)3Si)2Te were used as Ge and Te precursors, respectively. GeTe films were deposited at a low wafer temperature of 70–120 °C. To improve low reactivity of Ge(N(Si(CH3)3)2)2 toward ALD-type reaction with ((CH3)3Si)2Te, methanol vapor was coinjected with the Ge precursor and the Te precursor to form a reactive Ge intermediate having methoxy ligands and a Te intermediate having hydrogen ligands in the gas phase. This chemistry-specific ALD process deposited films various compositional GeTe alloys including the desired composition of Ge:Te = 1:1. Detailed mechanism study on the probable chemical reactions and film composition analysis revealed that the film growth could proceed via the formations of GeTe2, GeTe, and Ge2Te phases depending on the relative Ge-precursor concentration during the ALD process. The films showed feasibility for phase-ch...
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- 2016
10. Understanding the Coexistence of Two Bipolar Resistive Switching Modes with Opposite Polarity in Pt/TiO
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Hehe, Zhang, Sijung, Yoo, Stephan, Menzel, Carsten, Funck, Felix, Cüppers, Dirk J, Wouters, Cheol Seong, Hwang, Rainer, Waser, and Susanne, Hoffmann-Eifert
- Abstract
Redox-type resistive random access memories based on transition-metal oxides are studied as adjustable two-terminal devices for integrated network applications beyond von Neumann computing. The prevailing, so-called, counter-eight-wise (c8w) polarity of the switching hysteresis in filamentary-type valence change mechanism devices originates from a temperature- and field-controlled drift-diffusion process of mobile ions, predominantly oxygen vacancies in the switching oxide. Recently, a bipolar resistive switching (BRS) process with opposite polarity, so-called, eight-wise (8w) switching, has been reported that, especially for TiO
- Published
- 2018
11. Multicolor Changeable Optical Coating by Adopting Multiple Layers of Ultrathin Phase Change Material Film
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Cheol Seong Hwang, Sijung Yoo, Taeyong Eom, Sang Gyun Kim, and Taehong Gwon
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010302 applied physics ,Phase transition ,Materials science ,business.industry ,02 engineering and technology ,Optical storage ,021001 nanoscience & nanotechnology ,01 natural sciences ,Phase-change material ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,Amorphous solid ,law.invention ,Optical coating ,Optics ,law ,Optical cavity ,0103 physical sciences ,Optoelectronics ,Electrical and Electronic Engineering ,Crystallization ,0210 nano-technology ,business ,Layer (electronics) ,Biotechnology - Abstract
The multilayered optical coating whose structure consists of optical cavity and multiple layers of ultrathin phase change material (PCM) film is presented. The color changing is enabled via transition between amorphous and crystalline phases of PCM, which is accompanied by high optical contrast. The phase transition of each PCM layer, separated by ultrathin oxide barrier, can be realized through various crystallization temperatures with respect to the different thickness of ultrathin (
- Published
- 2016
12. Reducing the nano-scale defect formation of atomic-layer-deposited SrTiO3 films by adjusting the cooling rate of the crystallization annealing of the seed layer
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Woojin Jeon, Han Joon Kim, Min Jung Chung, Yeon Woo Yoo, Cheol Seong Hwang, Sijung Yoo, Woongkyu Lee, Cheol Hyun An, and Sang Woon Lee
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Materials science ,Annealing (metallurgy) ,Metals and Alloys ,Surfaces and Interfaces ,Dielectric ,Microstructure ,Thermal expansion ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,law.invention ,chemistry.chemical_compound ,Crystallography ,Atomic layer deposition ,chemistry ,law ,Materials Chemistry ,Strontium titanate ,Composite material ,Crystallization ,Thin film - Abstract
SrTiO3 (STO) thin films, grown by atomic layer deposition (ALD), were studied for capacitors in dynamic random access memory. The STO ALD process consisted of two steps: the growth of seed layer followed by a rapid thermal annealing (RTA) process at 650 °C to crystallize it, and the deposition of the main layer on top of the seed layer at 370 °C to induce the in-situ crystallization. During single cooling process after the RTA of the seed layer, voids and nano-cracks were formed due to the thermal expansion mismatch between STO film and Si substrate. This problem was well mitigated by adopting the stepwise cooling process, wherein the holding time of 30 s at 500, 350, and 200 °C suppressed the defect formation in the seed layer. Therefore, the main layer grown on that seed layer showed an improved microstructure with a high bulk dielectric constant of 135. However, the increase in total annealing time degraded the interface quality between the STO and the bottom electrode, which finally worsened the insulating property. As a result, the minimum equivalent oxide thicknesses with low leakage current densities (< 10− 7 A/cm2 at 0.8 V) for the single and stepwise cooling processes were 0.39 nm and 0.46 nm, respectively.
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- 2015
13. Atomic layer deposition of GeSe films using HGeCl
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Woohyun, Kim, Sijung, Yoo, Chanyoung, Yoo, Eui-Sang, Park, Jeongwoo, Jeon, Young Jae, Kwon, Kyung Seok, Woo, Han Joon, Kim, Yoon Kyeung, Lee, and Cheol Seong, Hwang
- Abstract
The ovonic threshold switch (OTS) based on the voltage snapback of amorphous chalcogenides possesses several desirable characteristics: bidirectional switching, a controllable threshold voltage (V
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- 2018
14. Structural Analyses of Phase Stability in Amorphous and Partially Crystallized Ge-Rich GeTe Films Prepared by Atomic Layer Deposition
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Eui-Sang Park, Sang Gyun Kim, Ahmed Yousef Mohamed, Han-Koo Lee, Taehong Gwon, Deok-Yong Cho, Chanyoung Yoo, Sijung Yoo, and Cheol Seong Hwang
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010302 applied physics ,X-ray absorption spectroscopy ,Materials science ,Absorption spectroscopy ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Amorphous solid ,Crystallography ,Atomic layer deposition ,symbols.namesake ,X-ray photoelectron spectroscopy ,0103 physical sciences ,symbols ,General Materials Science ,Crystallite ,0210 nano-technology ,Raman spectroscopy ,Phase diagram - Abstract
The local bonding structures of GexTe1-x (x = 0.5, 0.6, and 0.7) films prepared through atomic layer deposition (ALD) with Ge(N(Si(CH3)3)2)2 and ((CH3)3Si)2Te precursors were investigated using Ge K-edge X-ray absorption spectroscopy (XAS). The results of the X-ray absorption fine structure analyses show that for all of the compositions, the as-grown films were amorphous with a tetrahedral Ge coordination of a mixture of Ge-Te and Ge-Ge bonds but without any signature of Ge-GeTe decomposition. The compositional evolution in the valence band electronic structures probed through X-ray photoelectron spectroscopy suggests a substantial chemical influence of additional Ge on the nonstoichiometric GeTe. This implies that the ALD process can stabilize Ge-abundant bonding networks like -Te-Ge-Ge-Te- in amorphous GeTe. Meanwhile, the XAS results on the Ge-rich films that had undergone post-deposition annealing at 350 °C show that the parts of the crystalline Ge-rich GeTe became separated into Ge crystallites and rhombohedral GeTe in accordance with the bulk phase diagram, whereas the disordered GeTe domains still remained, consistent with the observations of transmission electron microscopy and Raman spectroscopy. Therefore, amorphousness in GeTe may be essential for the nonsegregated Ge-rich phases and the low growth temperature of the ALD enables the achievement of the structurally metastable phases.
- Published
- 2017
15. Nociceptive Memristor
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Yumin Kim, Young Jae Kwon, Dae Eun Kwon, Kyung Jean Yoon, Jung Ho Yoon, Sijung Yoo, Hae Jin Kim, Tae Hyung Park, Jin-Woo Han, Kyung Min Kim, and Cheol Seong Hwang
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Mechanics of Materials ,Mechanical Engineering ,General Materials Science ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,0210 nano-technology ,01 natural sciences ,0104 chemical sciences - Abstract
The biomimetic characteristics of the memristor as an electronic synapse and neuron have inspired the advent of new information technology in the neuromorphic computing. The application of the memristors can be extended to the artificial nerves on condition of the presence of electronic receptors which can transfer the external stimuli to the internal nerve system. In this work, nociceptor behaviors are demonstrated from the Pt/HfO
- Published
- 2017
16. Combined Ligand Exchange and Substitution Reactions in Atomic Layer Deposition of Conformal Ge2Sb2Te5 Film for Phase Change Memory Application
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Manchao Xiao, Taeyong Eom, Byung Joon Choi, Iain Buchanan, Sergei Vladimirovich Ivanov, Moo-Sung Kim, Sijung Yoo, Taehong Gwon, and Cheol Seong Hwang
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Substitution reaction ,Chemistry ,Ligand ,General Chemical Engineering ,Analytical chemistry ,Nanotechnology ,Conformal map ,General Chemistry ,Substrate (electronics) ,Contact hole ,Phase-change memory ,Atomic layer deposition ,Materials Chemistry ,Layer (electronics) - Abstract
For phase change memories application, Ge–Sb–Te films were prepared by a stable and reliable atomic layer deposition (ALD) method. Ge(OC2H5)4, Sb(OC2H5)3, [(CH3)3Si]3Sb, and [(CH3)3Si]2Te were used to deposit various layers with compositions that can be described by combinations of GeTe2–Sb2Te layers including Ge2Sb2Te5 at a substrate temperature as low as 70 °C. A shift in composition of Sb–Te films from Sb2Te3 to Sb2Te composition was achieved by combining ligand exchange and substitution reaction between Sb in [(CH3)3Si]3Sb and Te in the Sb2Te3 layer. This surface-limited ALD process allowed highly conformal, smooth, and reproducible film growth over a contact hole structure, highlighting the feasibility of phase change memory applications.
- Published
- 2015
17. Chemical interaction and ligand exchange between a [(CH3)3Si]3Sb precursor and atomic layer deposited Sb2Te3 films
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Sijung Yoo, Sergei Vladimirovich Ivanov, Byung Joon Choi, Moo-Sung Kim, Taeyong Eom, Manchao Xiao, Iain Buchanan, Taehong Gwon, Andrew Adamczyk, and Cheol Seong Hwang
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Materials science ,Trimethylsilyl ,Ligand ,General Chemistry ,Chemical interaction ,Crystallography ,chemistry.chemical_compound ,chemistry ,Materials Chemistry ,Organic chemistry ,Thin film ,Ternary operation ,Chemical composition ,Layer (electronics) ,Tie line - Abstract
The chemical interaction between the [(CH3)3Si]3Sb precursor and atomic layer deposited Sb2Te3 thin films was examined at temperatures ranging from 70 to 220 °C. The trimethylsilyl group [(CH3)3Si] displays greater affinity for Te than for Sb, and this drives replacement of Te in the film with Sb from the [(CH3)3Si]3Sb precursor, while eliminating volatile [(CH3)3Si]2Te, especially at elevated temperatures. The compositions of the resulting Sb–Te layers lie on the Sb2Te3–Sb tie line. The incorporation behavior of [(CH3)3Si]3Sb was explained in terms of a Lewis acid–base reaction. The exchange reactions occurred to relieve the unfavorable hard–soft Lewis acid–base pair between the trimethylsilyl group and Sb in [(CH3)3Si]3Sb. Such a reaction could be usefully adopted to control the chemical composition of ternary Ge–Sb–Te thin films.
- Published
- 2015
18. Bipolar resistive switching behavior of an amorphous Ge2Sb2Te5thin films with a Te layer
- Author
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Taeyong Eom, Cheol Seong Hwang, Sijung Yoo, and Taehong Gwon
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Materials science ,business.industry ,Transmission electron microscopy ,Electric field ,Electrode ,Optoelectronics ,General Materials Science ,Thin film ,Thermal conduction ,business ,Electrical conductor ,Amorphous solid ,Ion - Abstract
The mechanism of bipolar resistive switching (BRS) of amorphous Ge2Sb2Te5 (GST) thin films sandwiched between inert electrodes (Ti and Pt) was examined. Typical bipolar resistive switching behavior with a high resistance ratio (∼103) and reliable switching characteristics was achieved. High-resolution transmission electron microscopy revealed the presence of a conductive Te-filament bridging between the top and bottom electrodes through an amorphous GST matrix. The conduction mechanism analysis showed that the low-resistance state was semiconducting and dominated by band transport, whereas Poole–Frenkel conduction governed the carrier transport in the high-resistance state. Thus, the BRS behavior can be attributed to the formation and rupture of the semiconducting conductive Te bridge through the migration of the Te ions in the amorphous GST matrix under a high electric field. The Te ions are provided by the thin (∼5 nm) Te-rich layer formed at the bottom electrode interface.
- Published
- 2015
19. Next-Generation Memory: Double-Layer-Stacked One Diode-One Resistive Switching Memory Crossbar Array with an Extremely High Rectification Ratio of 109 (Adv. Electron. Mater. 7/2017)
- Author
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Sijung Yoo, Yu Min Kim, Cheol Seong Hwang, Gun Hwan Kim, Jung Ho Yoon, Dae Eun Kwon, Woorham Bae, Kyung Jean Yoon, Hae Jin Kim, Yeong Jae Kwon, and Tae Hyung Park
- Subjects
Double layer (biology) ,Materials science ,business.industry ,0211 other engineering and technologies ,Nanotechnology ,02 engineering and technology ,Electron ,Crossbar array ,Electronic, Optical and Magnetic Materials ,Rectification ,Optoelectronics ,Resistive switching memory ,business ,021106 design practice & management ,Diode - Published
- 2017
20. Influence of the Kinetic Adsorption Process on the Atomic Layer Deposition Process of (GeTe2)(1–x)(Sb2Te3)x Layers Using Ge4+–Alkoxide Precursors
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Moo-Sung Kim, Sijung Yoo, Byung Joon Choi, Taeyong Eom, Manchao Xiao, Iain Buchanan, Taehong Gwon, and Cheol Seong Hwang
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General Chemical Engineering ,Nanotechnology ,General Chemistry ,Desorption kinetics ,chemistry.chemical_compound ,Atomic layer deposition ,Adsorption ,chemistry ,Physisorption ,Adsorption kinetics ,Scientific method ,Alkoxide ,Materials Chemistry ,Physical chemistry ,Layer (electronics) - Abstract
(GeTe2)(1–x)(Sb2Te3)x (GST) layers were deposited via atomic layer deposition (ALD) at growth temperatures ranging from 50 to 120 °C using Ge(OCH3)4 or Ge(OC2H5)4, Sb(OC2H5)3, and [(CH3)3Si]2Te as the metal–organic precursors of the Ge, Sb, and Te elements, respectively. The GST layers with compositions lying on the GeTe2–Sb2Te3 tie lines could be obtained by varying the ratio of the Ge–Te and Sb–Te ALD cycles. Although the incorporation of an Sb–Te layer into the GST film occurred in a genuine ALD manner, that of the Ge–Te layer was governed by the kinetically limited physisorption of Ge precursors. The incorporation behavior of the Ge precursor with different ligands was explained by the adsorption and desorption kinetics based on the Brunauer–Emmett–Teller isotherm. The ALD-like film growth behavior could be well-explained by the kinetically limited incorporation of Ge atoms.
- Published
- 2014
21. Electrical Properties of ZrO2 /Al2 O3 /ZrO2 -Based Capacitors with TiN, Ru, and TiN/Ru Top Electrode Materials
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Woojin Jeon, Min Jung Chung, Woongkyu Lee, Cheol Seong Hwang, Sang Hyeon Kim, Cheol Hyun An, and Sijung Yoo
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010302 applied physics ,Electrode material ,Materials science ,business.industry ,chemistry.chemical_element ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,law.invention ,Capacitor ,chemistry ,law ,0103 physical sciences ,Electrode ,Optoelectronics ,General Materials Science ,0210 nano-technology ,Tin ,business - Published
- 2018
22. Uniform Self-rectifying Resistive Switching Behavior via Preformed Conducting Paths in a Vertical-type Ta2O5/HfO2-x Structure with a Sub-μm(2) Cell Area
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Tae Hyung Park, Jung Ho Yoon, Hye-Jin Kim, Young Jae Kwon, Xing Long Shao, Seul Ji Song, Yumin Kim, Dae Eun Kwon, Cheol Seong Hwang, Kyung Jean Yoon, and Sijung Yoo
- Subjects
010302 applied physics ,Materials science ,Fabrication ,business.industry ,Process (computing) ,chemistry.chemical_element ,Nanotechnology ,02 engineering and technology ,Type (model theory) ,021001 nanoscience & nanotechnology ,01 natural sciences ,Vertical integration ,Resistive random-access memory ,chemistry ,Memory cell ,0103 physical sciences ,Optoelectronics ,General Materials Science ,0210 nano-technology ,business ,Tin ,Scaling - Abstract
To replace or succeed the present NAND flash memory, resistive switching random access memory (ReRAM) should be implemented in the vertical-type crossbar array configuration. The ReRAM cell must have a highly reproducible resistive switching (RS) performance and an electroforming-free, self-rectifying, low-power-consumption, multilevel-switching, and easy fabrication process with a deep sub-μm(2) cell area. In this work, a Pt/Ta2O5/HfO2-x/TiN RS memory cell fabricated in the form of a vertical-type structure was presented as a feasible contender to meet the above requirements. While the fundamental RS characteristics of this material based on the electron trapping/detrapping mechanisms have been reported elsewhere, the influence of the cell scaling size to 0.34 μm(2) on the RS performance by adopting the vertical integration scheme was carefully examined in this work. The smaller cell area provided much better switching uniformity while all the other benefits of this specific material system were preserved. Using the overstressing technique, the nature of RS through the localized conducting path was further examined, which elucidated the fundamental difference between the present material system and the general ionic-motion-related bipolar RS mechanism.
- Published
- 2016
23. Resistance switching behavior of atomic layer deposited SrTiO$_{3}$ film through possible formation of Sr$_{2}$Ti$_{6}$O$_{13}$ or Sr$_{1}$Ti$_{11}$O$_{20}$ phases
- Author
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Kyung Jean Yoon, Woongkyu Lee, Sijung Yoo, Hye Jung Chang, Rainer Waser, Jung-Hae Choi, Cheol Seong Hwang, Susanne Hoffmann-Eifert, and In Won Yeu
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010302 applied physics ,Multidisciplinary ,Oxide ,chemistry.chemical_element ,02 engineering and technology ,021001 nanoscience & nanotechnology ,computer.software_genre ,01 natural sciences ,Article ,Characterization (materials science) ,chemistry.chemical_compound ,chemistry ,Transmission electron microscopy ,Chemical physics ,Phase (matter) ,0103 physical sciences ,ddc:000 ,Grain boundary ,Data mining ,Thin film ,0210 nano-technology ,Tin ,Layer (electronics) ,computer - Abstract
Identification of microstructural evolution of nanoscale conducting phase, such as conducting filament (CF), in many resistance switching (RS) devices is a crucial factor to unambiguously understand the electrical behaviours of the RS-based electronic devices. Among the diverse RS material systems, oxide-based redox system comprises the major category of these intriguing electronic devices, where the local, along both lateral and vertical directions of thin films, changes in oxygen chemistry has been suggested to be the main RS mechanism. However, there are systems which involve distinctive crystallographic phases as CF; the Magnéli phase in TiO2 is one of the very well-known examples. The current research reports the possible presence of distinctive local conducting phase in atomic layer deposited SrTiO3 RS thin film. The conducting phase was identified through extensive transmission electron microscopy studies, which indicated that oxygen-deficient Sr2Ti6O13 or Sr1Ti11O20 phase was presumably present mainly along the grain boundaries of SrTiO3 after the unipolar set switching in Pt/TiN/SrTiO3/Pt structure. A detailed electrical characterization revealed that the samples showed typical bipolar and complementary RS after the memory cell was unipolar reset.
- Published
- 2016
24. Giant Dielectric Permittivity in Ferroelectric Thin Films: Domain Wall Ping Pong
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James F. Scott, Cheol Seong Hwang, Min Hyuk Park, Sijung Yoo, Yu Jin Kim, An Quan Jiang, David Wei Zhang, Xiang Jian Meng, University of St Andrews. School of Chemistry, and University of St Andrews. School of Physics and Astronomy
- Subjects
Multidisciplinary ,Condensed matter physics ,Computer science ,Orders of magnitude (temperature) ,Nucleation ,NDAS ,Dielectric ,Dielectric thin films ,Bioinformatics ,Lead zirconate titanate ,Ferroelectricity ,Grain size ,Article ,law.invention ,Anode ,Switching time ,Capacitor ,chemistry.chemical_compound ,QC Physics ,chemistry ,law ,Thin film ,QC - Abstract
This study was supported by the National Key Basic Research Program of China (No. 2014CB921004), the National Natural Science Foundation of China (Nos. 61225020 and 61176121), and the Program for Professor of Special Appointment (Eastern Scholar) in Shanghai. C.S.H. acknowledges the support of the Global Research Laboratory Program (2012040157) through the National Research Foundation (NRF) of Korea. Date of Acceptance: 02/09/2015 The dielectric permittivity in ferroelectric thin films is generally orders of magnitude smaller than in their bulk. Here, we discover a way of increasing dielectric constants in ferroelectric thin films by ca. 500% by synchronizing the pulsed switching fields with the intrinsic switching time (nucleation of domain plus forward growth from cathode to anode). In a 170-nm lead zirconate titanate thin film with an average grain size of 850' this produces a dielectric constant of 8200 with the maximum nucleus density of 3.8 μ1-2, which is one to three orders of magnitude higher than in other dielectric thin films. This permits smaller capacitors in memory devices and is a step forward in making ferroelectric domain-engineered nano-electronics. Publisher PDF
- Published
- 2015
- Full Text
- View/download PDF
25. Atomic layer deposition of GeSe films using HGeCl3and [(CH3)3Si]2Se with the discrete feeding method for the ovonic threshold switch
- Author
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Eui-Sang Park, Young Jae Kwon, Yoon Kyeung Lee, Jeongwoo Jeon, Chanyoung Yoo, Woohyun Kim, Han Joon Kim, Cheol Seong Hwang, Kyung Seok Woo, and Sijung Yoo
- Subjects
010302 applied physics ,Materials science ,Fabrication ,Mechanical Engineering ,Analytical chemistry ,Bioengineering ,02 engineering and technology ,General Chemistry ,Substrate (electronics) ,021001 nanoscience & nanotechnology ,01 natural sciences ,Amorphous solid ,Threshold voltage ,Atomic layer deposition ,Mechanics of Materials ,0103 physical sciences ,General Materials Science ,Electrical and Electronic Engineering ,Thin film ,0210 nano-technology ,Saturation (magnetic) ,Stoichiometry - Abstract
The ovonic threshold switch (OTS) based on the voltage snapback of amorphous chalcogenides possesses several desirable characteristics: bidirectional switching, a controllable threshold voltage (V th) and processability for three-dimensional stackable devices. Among the materials that can be used as OTS, GeSe has a strong glass-forming ability (∼350 °C crystallization temperature), with a simple binary composition. Described herein is a new method of depositing GeSe films through atomic layer deposition (ALD), using HGeCl3 and [(CH3)3Si]2Se as Ge and Se precursors, respectively. The stoichiometric GeSe thin films were formed through a ligand exchange reaction between the two precursor molecules, without the adoption of an additional reaction gas, at low substrate temperatures ranging from 70 °C-150 °C. The pseudo-saturation behavior required a long time of Ge precursor injection to achieve the saturation growth rate. This was due to the adverse influence of the physisorbed precursor and byproduct molecules on the efficient chemical adsorption reaction between the precursors and reaction sites. To overcome the slow saturation and excessive use of the Ge precursor, the discrete feeding method (DFM), where HGeCl3 is supplied multiple times consecutively with subdivided pulse times, was adopted. DFM led to the saturation of the GeSe growth rate at a much shorter total injection time of the Ge precursor, and improved the film density and oxidation resistance properties. The GeSe film grown via DFM exhibited a short OTS time of ∼40 ns, a ∼107 ON/OFF current ratio, and ∼104 selectivity. The OTS behavior was consistent with the modified Poole-Frenkel mechanism in the OFF state. In contrast, the similar GeSe film grown through the conventional ALD showed a low density and high vulnerability to oxidation, which prevented the OTS performance. The ALD method of GeSe films introduced here will contribute to the fabrication of a three-dimensionally integrated memory as a selector device for preventing sneak current.
- Published
- 2018
26. Electronic resistance switching in the Al/TiO(x)/Al structure for forming-free and area-scalable memory
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Sijung Yoo, Kai Liang Zhang, Xing Long Shao, Cheol Seong Hwang, Li Wei Zhou, Hao Jiang, Kyung Jean Yoon, and Jin Shi Zhao
- Subjects
business.industry ,Chemistry ,Nanotechnology ,Trapping ,Electron ,Transmission electron microscopy ,Electrode ,Optoelectronics ,Rectangular potential barrier ,General Materials Science ,business ,Ternary operation ,Layer (electronics) ,Characteristic energy - Abstract
Electronic bipolar resistance switching (eBRS) in an Al/TiOx/Al structure, where the TiOx layer was reactively sputter-deposited, was examined in conjunction with a structural analysis using transmission electron microscopy. A thin (3–5 nm) insulating Al(Ti)Ox layer was formed at the bottom Al electrode interface, which provided the necessary asymmetric potential barrier for the eBRS to emerge, whereas the top Al electrode interface appeared to have provided the fluent carrier (electron) injection. The set and reset switching were related to the trapping and detrapping of the carriers at the trap centers, the characteristic energy of which was ∼0.86 eV, across the entire electrode area. The general features of this material system as the feasible RS memory were insufficient: endurance cycle
- Published
- 2015
27. Bipolar resistive switching behavior of an amorphous Ge₂Sb₂Te₅ thin films with a Te layer
- Author
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Sijung, Yoo, Taeyong, Eom, Taehong, Gwon, and Cheol Seong, Hwang
- Abstract
The mechanism of bipolar resistive switching (BRS) of amorphous Ge2Sb2Te5 (GST) thin films sandwiched between inert electrodes (Ti and Pt) was examined. Typical bipolar resistive switching behavior with a high resistance ratio (∼10(3)) and reliable switching characteristics was achieved. High-resolution transmission electron microscopy revealed the presence of a conductive Te-filament bridging between the top and bottom electrodes through an amorphous GST matrix. The conduction mechanism analysis showed that the low-resistance state was semiconducting and dominated by band transport, whereas Poole-Frenkel conduction governed the carrier transport in the high-resistance state. Thus, the BRS behavior can be attributed to the formation and rupture of the semiconducting conductive Te bridge through the migration of the Te ions in the amorphous GST matrix under a high electric field. The Te ions are provided by the thin (∼5 nm) Te-rich layer formed at the bottom electrode interface.
- Published
- 2015
28. Evaluating the top electrode material for achieving an equivalent oxide thickness smaller than 0.4 nm from an Al-doped TiO₂ film
- Author
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Woojin, Jeon, Sijung, Yoo, Hyo Kyeom, Kim, Woongkyu, Lee, Cheol Hyun, An, Min Jung, Chung, Cheol Jin, Cho, Seong Keun, Kim, and Cheol Seong, Hwang
- Abstract
The effects of Pt and RuO2 top electrodes on the electrical properties of capacitors with Al-doped TiO2 (ATO) films grown on the RuO2 bottom electrode by an atomic layer deposition method were examined. The rutile phase ATO films with high bulk dielectric constant (80) were well-grown because of the local epitaxial relationship with the rutile structured RuO2 bottom electrode. However, the interface between top electrode and ATO was damaged during the sputtering process of the top electrode, resulting in the decrease in the dielectric constant. Postmetallization annealing at 400 °C was performed to mitigate the sputtering damage. During the postmetallization annealing, the ATO layer near the RuO2 top electrode/ATO interface was well-crystallized because of the structural compatibility between RuO2 and rutile ATO, while the ATO layer near the Pt top electrode/ATO interface still exhibited an amorphous-like structure. Despite the same thickness of the ATO films, therefore, the capacitors with RuO2 top electrodes showed higher capacitance compared to the capacitors with Pt top electrodes. Eventually, an extremely low equivalent oxide thickness of 0.37 nm with low enough leakage current density (1 × 10(-7) A/cm(2) at 0.8 V) and physical thickness of 8.7 nm for the next-generation dynamic random access memory was achieved from ATO films with RuO2 top electrodes.
- Published
- 2014
29. Double-Layer-Stacked One Diode-One Resistive Switching Memory Crossbar Array with an Extremely High Rectification Ratio of 109
- Author
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Yeong Jae Kwon, Gun Hwan Kim, Hae Jin Kim, Kyung Jean Yoon, Jung Ho Yoon, Sijung Yoo, Cheol Seong Hwang, Yu Min Kim, Tae Hyung Park, Dae Eun Kwon, and Woorham Bae
- Subjects
010302 applied physics ,Materials science ,Fabrication ,business.industry ,Schottky diode ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Electronic, Optical and Magnetic Materials ,law.invention ,Non-volatile memory ,Rectification ,Interference (communication) ,law ,Physical vapor deposition ,0103 physical sciences ,Electronic engineering ,Optoelectronics ,Resistor ,0210 nano-technology ,business ,Diode - Abstract
A double-layer-stacked 1 diode-1 resistor (1D1R) cross-bar array (CBA) resistance switching random access memory is fabricated. The TiO2-based Schottky diode and the unipolar resistance switching TiO2 comprise the cell selector and nonvolatile memory components, respectively. All the fabrication processes are performed near room temperature through physical vapor deposition processes, and the performance degradation by the thermal budget is well suppressed. As a result, a rectification ratio as high as 1.4 × 109 is achieved from the appropriately cycled diode, which can last up to 108 cycles in the integrated structure. Such highly promising performance is confirmed from both the upper and lower memory layers, which confirm the possible route for the multistacked memory structure. The two-bit-per-cell operation allows an effective minimum cell area of F2, which is confirmed from the randomly accessed cells to be completely free from adverse interference through the adoption of an extremely-high-performance diode. The present 1D1R integration technique will eventually allow the fabrication of an extremely high-integration-density (above 1 Gb per block) CBA with the help of the two-port sensing scheme. Such a high-performance CBA device is a feasible contender for memory-dominant computation.
- Published
- 2017
30. Fermi-level unpinning in Pt/Al2O3/GaSb PMOS capacitors by sulphurization and rapid thermal annealing of GaSb surfaces
- Author
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Seongkyung Kim, Jae Kyeong Jeong, Hyeong Joon Kim, Ha-Jin Lim, Sijung Yoo, and Joon-Rae Kim
- Subjects
010302 applied physics ,Range (particle radiation) ,Materials science ,Physics and Astronomy (miscellaneous) ,business.industry ,Fermi level ,chemistry.chemical_element ,02 engineering and technology ,Dielectric ,021001 nanoscience & nanotechnology ,01 natural sciences ,PMOS logic ,law.invention ,symbols.namesake ,Capacitor ,Semiconductor ,chemistry ,law ,0103 physical sciences ,symbols ,Optoelectronics ,Rapid thermal annealing ,0210 nano-technology ,business ,Platinum - Abstract
A facile route to mitigate the Fermi-level pinning between a p-type GaSb semiconductor and an Al2O3 dielectric is proposed. Combination of the sulphurization of the GaSb surface and the subsequent rapid thermal annealing allowed for high quality GaSb/Al2O3 interfacial characteristics; the interfacial trap density value was ≤2.0 × 1012 cm−2 eV−1 in an energy range of 0.05 ≤ ET − Ev ≤ 0.45 eV for the PMOS capacitor via rapid thermal annealing at 575 °C. A physical rationale was given on the basis of the thermo-chemical conversion of Ga2O into Ga2O3 and the conformal elimination of Sb related elements and oxides on the GaSb surface.
- Published
- 2016
31. Atomic Layer Deposition of GeTe and Ge-Sb-Te Films Using HGeCl3, Sb(OC2H5)3, and {(CH3)3Si}2Te and Their Reaction Mechanisms.
- Author
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Taehong Gwon, Taeyong Eom, Sijung Yoo, Chanyoung Yoo, Eui-sang Park, Sanggyun Kim, Moo-Sung Kim, Buchanan, Iain, Manchao Xiao, Ivanov, Sergei, and Cheol Seong Hwang
- Published
- 2017
- Full Text
- View/download PDF
32. Atomic Layer Deposition of GeTe Films Using Ge{N[Si(CH3)3]2}2, {(CH3)3Si}2Te, and Methanol.
- Author
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Taehong Gwon, Taeyong Eom, Sijung Yoo, Han-Koo Lee, Deok-Yong Cho, Moo-Sung Kim, Buchanan, Iain, Manchao Xiao, Ivanov, Sergei, and Cheol Seong Hwang
- Published
- 2016
- Full Text
- View/download PDF
33. Fermi-level unpinning in Pt/Al2O3/GaSb PMOS capacitors by sulphurization and rapid thermal annealing of GaSb surfaces.
- Author
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Seongkyung Kim, Sijung Yoo, Hajin Lim, Joon-Rae Kim, Jae Kyeong Jeong, and Hyeong Joon Kim
- Subjects
- *
SEMICONDUCTORS , *DIELECTRICS , *ANNEALING of metals , *OXIDES , *OXYGEN compounds - Abstract
A facile route to mitigate the Fermi-level pinning between a p-type GaSb semiconductor and an Al 2O3 dielectric is proposed. Combination of the sulphurization of the GaSb surface and the subsequent rapid thermal annealing allowed for high quality GaSb/Al2O3 interfacial characteristics; the interfacial trap density value was ≤2.0 x 1012 cm-2 eV-1 in an energy range of 0.05 ≤ET -- Ev ≤0.45 eV for the PMOS capacitor via rapid thermal annealing at 575 °C. A physical rationale was given on the basis of the thermo-chemical conversion of Ga2O into Ga2O3 and the conformal elimination of Sb related elements and oxides on the GaSb surface. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
34. Giant Dielectric Permittivity in Ferroelectric Thin Films: Domain Wall Ping Pong.
- Author
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An Quan Jiang, Xiang Jian Meng, Wei Zhang, David, Min Hyuk Park, Sijung Yoo, Yu Jin Kim, Scott, James F., and Cheol Seong Hwang
- Subjects
DIELECTRIC films ,FERROELECTRIC thin films ,CATHODES ,ANODES ,COMPOUND nucleus - Abstract
The dielectric permittivity in ferroelectric thin films is generally orders of magnitude smaller than in their bulk. Here, we discover a way of increasing dielectric constants in ferroelectric thin films by ca. 500% by synchronizing the pulsed switching fields with the intrinsic switching time (nucleation of domain plus forward growth from cathode to anode). In a 170-nm lead zirconate titanate thin film with an average grain size of 850 nm this produces a dielectric constant of 8200 with the maximum nucleus density of 3.8 μm
-2 , which is one to three orders of magnitude higher than in other dielectric thin films. This permits smaller capacitors in memory devices and is a step forward in making ferroelectric domain-engineered nano-electronics. [ABSTRACT FROM AUTHOR]- Published
- 2015
- Full Text
- View/download PDF
35. Combined Ligand Exchange and Substitution Reactionsin Atomic Layer Deposition of Conformal Ge2Sb2Te5Film for Phase Change Memory Application.
- Author
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Taeyong Eom, Taehong Gwon, Sijung Yoo, ByungJoon Choi, Moo-Sung Kim, Iain Buchanan, Sergei Ivanov, Manchao Xiao, and Cheol Seong Hwang
- Published
- 2015
- Full Text
- View/download PDF
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