Browsing by Author "Chou, Cheng-Tung"

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Electrode dependence of filament formation in HfO(2) resistive-switching memory
(2011-04-15)
Lin, Kuan-Liang
;
Hou, Tuo-Hung
;
Shieh, Jiann
;
Lin, Jun-Hung
;
Chou, Cheng-Tung
This study investigates bipolar and nonpolar resistive-switching of HfO(2) with various metal electrodes. Supported by convincing physical and electrical evidence, it is our contention that the composition of conducting filaments in HfO(2) strongly depends upon the metal electrodes. Nonpolar resistive-switching with the Ni electrode is attributed to the migration of metal cations and the corresponding electrochemical metallization. Conversely, oxygen-deficient filaments induced by anion migration are responsible for bipolar resistive-switching. It was also found that the characteristic nature of the conducting filaments influences many aspects of switching characteristics, including the switching power, cycling variations, and retention at elevated temperatures. (C) 2011 American Institute of Physics. [doi:10.1063/1.3567915]
Electrode dependence of filament formation in HfO2 resistive-switching memory
(2011-04-15)
Lin, Kuan-Liang
;
Hou, Tuo-Hung
;
Shieh, Jiann
;
Lin, Jun-Hung
;
Chou, Cheng-Tung
This study investigates bipolar and nonpolar resistive-switching of HfO2 with various metal electrodes. Supported by convincing physical and electrical evidence, it is our contention that the composition of conducting filaments in HfO2 strongly depends upon the metal electrodes. Nonpolar resistive-switching with the Ni electrode is attributed to the migration of metal cations and the corresponding electrochemical metallization. Conversely, oxygen-deficient filaments induced by anion migration are responsible for bipolar resistive-switching. It was also found that the characteristic nature of the conducting filaments influences many aspects of switching characteristics, including the switching power, cycling variations, and retention at elevated temperatures. (C) 2011 American Institute of Physics. [doi:10.1063/1.3567915]
Evolution of RESET current and filament morphology in low-power HfO(2) unipolar resistive switching memory
(2011-03-07)
Hou, Tuo-Hung
;
Lin, Kuan-Liang
;
Shieh, Jiann
;
Lin, Jun-Hung
;
Chou, Cheng-Tung
Reduction in RESET current is crucial for future high-density resistive-switching memory. We have reported a unipolar-switching Ni/HfO(2)/Si structure with low RESET current of 50 mu A and RESET power of 30 mu W. In addition, a unique cycling evolution of RESET current across more than two orders of magnitude allows us to probe into the evolvement of filament morphology at nanoscale, using a simple yet quantitative model. Filament morphology was found to depend strongly on the charge-dissipation current proportional to the powers of SET voltage. Moreover, the formation of inactive semiconductive filaments plays an important role in the reduction in RESET current. (C) 2011 American Institute of Physics. [doi:10.1063/1.3565239]
Evolution of RESET current and filament morphology in low-power HfO2 unipolar resistive switching memory
(2011-03-07)
Hou, Tuo-Hung
;
Lin, Kuan-Liang
;
Shieh, Jiann
;
Lin, Jun-Hung
;
Chou, Cheng-Tung
Reduction in RESET current is crucial for future high-density resistive-switching memory. We have reported a unipolar-switching Ni/HfO2/Si structure with low RESET current of 50 mu A and RESET power of 30 mu W. In addition, a unique cycling evolution of RESET current across more than two orders of magnitude allows us to probe into the evolvement of filament morphology at nanoscale, using a simple yet quantitative model. Filament morphology was found to depend strongly on the charge-dissipation current proportional to the powers of SET voltage. Moreover, the formation of inactive semiconductive filaments plays an important role in the reduction in RESET current. (C) 2011 American Institute of Physics. [doi:10.1063/1.3565239]
Fabrication and enhanced field emission properties of novel silicon nanostructures
(2010-12-01)
Ravipati, Srikanth
;
Kuo, Chang-Jung
;
Shieh, Jiann
;
Chou, Cheng-Tung
;
Ko, Fu-Hsiang
We reported the fabrication and the field emission properties of two-tier novel silicon nanostructures. First, silicon nanopillars with ordered high aspect ratio were achieved by using conventional lithographic techniques to act as the field emission sources. Second, sharp-edged well-aligned silicon nanograss was fabricated on top of the nanopillars by means of hydrogen plasma dry etching to induce the field emission characteristics. The turn-on fields were obtained as 10.5 and 14.4 V/mu m under current density of 0.01 mA/cm(2) for two-tier patterns separated by respective 5 mu m and 2 mu m spaces. The excellent field emission property from these novel nanostructures exhibited a great potential as high-performance field emitter arrays towards future nanoelectronic devices. (C) 2010 Elsevier Ltd. All rights reserved.
Large-Area 2D Layered MoTe2 by Physical Vapor Deposition and Solid-Phase Crystallization in a Tellurium-Free Atmosphere
(2017-09-08)
Huang, Jyun-Hong
;
Deng, Kuang-Ying
;
Liu, Pang-Shiuan
;
Wu, Chien-Ting
;
Chou, Cheng-Tung
Molybdenum ditelluride (MoTe2) has attracted considerable interest for nanoelectronic, optoelectronic, spintronic, and valleytronic applications because of its modest band gap, high field-effect mobility, large spin-orbit-coupling splitting, and tunable 1T/2H phases. However, synthesizing large-area, high-quality MoTe2 remains challenging. The complicated design of gas-phase reactant transport and reaction for chemical vapor deposition or tellurization is nontrivial because of the weak bonding energy between Mo and Te. This study reports a new method for depositing MoTe2 that entails using physical vapor deposition followed by a postannealing process in a Te-free atmosphere. Both Mo and Te are physically deposited onto the substrate by sputtering a MoTe2 target. A composite SiO2 capping layer is designed to prevent Te sublimation during the postannealing process. The postannealing process facilitates 1T-to-2H phase transition and solid-phase crystallization, leading to the formation of high-crystallinity few-layer 2H-MoTe2 with a field-effect mobility of approximate to 10 cm(2) V-1 s(-1), the highest among all nonexfoliated 2H-MoTe2 currently reported. Furthermore, 2H-MoS2 and Td-WTe2 can be deposited using similar methods. Requiring no transfer or chemical reaction of metal and chalcogen reactants in the gas phase, the proposed method is potentially a general yet simple approach for depositing a wide variety of large-area, high-quality, 2D layered structures.
Large-area few-layer MoS2 deposited by sputtering
(2016-06)
Huang, Jyun-Hong
;
Chen, Hsing-Hung
;
Liu, Pang-Shiuan
;
Lu, Li-Syuan
;
Wu, Chien-Ting
Direct magnetron sputtering of transition metal dichalcogenide targets is proposed as a new approach for depositing large-area two-dimensional layered materials. Bilayer to few-layer MoS2 deposited by magnetron sputtering followed by post-deposition annealing shows superior area scalability over 20 cm(2) and layer-by-layer controllability. High crystallinity of layered MoS2 was confirmed by Raman, photo-luminescence, and transmission electron microscopy analysis. The sputtering temperature and annealing ambience were found to play an important role in the film quality. The top-gate field-effect transistor by using the layered MoS2 channel shows typical n-type characteristics with a current on/off ratio of approximately 10(4). The relatively low mobility is attributed to the small grain size of 0.1-1 mu m with a trap charge density in grain boundaries of the order of 10(13) cm(-2).
Polybenzoxazine as a mold-release agent for nanoimprint lithography
(2007-05-22)
Wang, Chih-Feng
;
Chiou, Shih-Feng
;
Ko, Fu-Hsiang
;
Chen, Jem-Kun
;
Chou, Cheng-Tung
One of the most important tasks remaining to be resolved in nanoimprint lithography is the elimination of the resist sticking to the mold during demolding. Previously, the main approach was to apply a thin layer of fluorinated alkyl silane mold-release agent on the surface on the mold; however, this involves complicated steps and high costs. The low surface free energy material polybenzoxazine provides an efficient mold-release agent for silicon molds that is easier to process, costs less, and has no side reactions.
Switching Mode and Mechanism in Binary Oxide Resistive Random Access Memory Using Ni Electrode
(2013-03-01)
Lin, Kuan-Liang
;
Hou, Tuo-Hung
;
Lee, Yao-Jen
;
Chang, Jhe-Wei
;
Lin, Jun-Hung
Resistive-switching (RS) modes in different CMOS-compatible binary oxides have been shown to be governed by the interplay with the Ni top electrode. Unipolar RS and metallic low-resistance state in polycrystalline HfO2 and ZrO2 are distinct from the preferential bipolar RS and semiconductive low-resistance state in amorphous Al2O3 and SiO2. Backside secondary ion mass spectrometry (SIMS) has shown the formation of Ni filaments in HfO2, in contrast to the formation of oxygen-vacancy filaments in Al2O3. The differences have been explained by strong dependence of Ni migration on the oxide crystallinity. Additionally, the RS mode can be further tailored using bilayer structures. The oxide layer next to the Si bottom electrode and its tendency of forming Ni filaments play significant roles in unipolar RS in the bilayer structures, in support of the conical-shape Ni filament model where the connecting and rupture of filaments for unipolar RS occur at the smallest diameter near the bottom electrodes. (c) 2013 The Japan Society of Applied Physics