Browsing by Author "Hsu, Kai-Chieh"

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A Comprehensive Study of 3-stage High Resistance State Retention Behavior for TMO ReRAMs from Single Cells to a Large Array
(2017-01-01)
Lin, Yu-Hsuan
;
Ho, Yung-Han
;
Lee, Ming-Hsiu
;
Wang, Chao-Hung
;
Lin, Yu-Yu
For the first time the retention of high resistance state (HRS) in resistive random access memory (ReRAM) is found to compose of three stages - extending tail-bits, distribution shift, and then distribution broadening. This work provides a comprehensive study on the HRS's retention behavior in WOx-based ReRAMs from single device characteristics to group distribution. Different from conventional activation energy (Ea) analysis, the mean and variance of the array distribution are presented to overcome the non-uniform Ea issue. Since the extracted Ea fits well with Vo(2+) (oxygen vacancy) migration characteristics, the three retention stages are suggested to be the competing results from the migration, recombination, and generation of the Vo(2+) and O2- in the gap region. A three-dimensional retention model with kinetic Monte Carlo simulator and trap-assisted tunneling conduction is proposed to discuss the dominating mechanism in different time and temperature scales. The mechanism for random telegraph noise is also included to illustrate the fluctuating nature of the HRS cells.
One-step vapor-solid reaction growth of Sn@C core-shell nanowires as an anode material for Li-ion batteries
(2012-10-28)
Hsu, Kai-Chieh
;
Liu, Chia-Erh
;
Chen, Po-Chin
;
Lee, Chi-Young
;
Chiu, Hsin-Tien
Sn@C core-shell nanowires (NWs) were synthesized by reacting SnO2 particles with a flowing mixture of C2H2 and Ar gases at elevated temperatures. The overall diameter of the core-shell nanostructure was 100-350 nm. The C shell thickness was 30-70 nm. The NW length was several micrometers. Inside the shell, a void space was found. The reaction is proposed to be via a vapor-solid reaction growth (VSRG) pathway. The NWs were investigated as a potential anode material for Li-ion batteries (LIBs). The half-cell constructed from the as-fabricated electrode and a Li foil exhibited a reversible capacity of 525 mA h g(-1) after one hundred cycles at a current density of 100 mA g(-1). At a current density as high as 1000 mA g(-1), the battery still maintained a capacity of 486 mA h g(-1). The excellent performance is attributed to the unique 1D core-shell morphology. The core-shell structure and the void space inside the shell can accommodate large volume changes caused by the formation and decomposition of LixSn alloys in the charge-discharge steps.
Vapour solid reaction growth of SnO2 nanorods as an anode material for Li ion batteries
(2014-01-01)
Hsu, Kai-Chieh
;
Lee, Chi-Young
;
Chiu, Hsin-Tien
;
應用化學系
;
Department of Applied Chemistry
Via a vapour-solid reaction growth (VSRG) pathway, phase-segregated SnO2 nanorods (NRs, length 1-2 mu m and diameter 10-20 nm) were developed in a matrix of CaCl2 salt by reacting CaO particles with a flowing mixture of SnCl4 and Ar gases at elevated temperatures. The SnO2 NRs were investigated as a potential anode material for Li-ion batteries (LIBs). A half-cell constructed from the as-fabricated SnO2 electrode and a Li foil exhibited a reversible capacity 435 mA h g(-1) after one hundred cycles at a current density of 100 mA g(-1) (0.13 C). The SnO2 NRs exhibited much better Li storage properties, higher reversible capacity and cyclic capacity retention after extended cycling, than commercial SnO2 particles did. The improved electrochemical performance is attributed to the presence of an inactive amorphous byproduct matrix, which contains Li2O, the decomposed electrolyte, and the solid electrolyte interphase (SEI), among the reduced NRs. The matrix probably buffered and reduced the stress caused by the volume change of the electrode during the charge-discharge cyclings.
Vapour solid reaction growth of SnO2 nanorods as an anode material for Li ion batteries
(2014-01-01)
Hsu, Kai-Chieh
;
Lee, Chi-Young
;
Chiu, Hsin-Tien
;
應用化學系
;
Department of Applied Chemistry
Via a vapour-solid reaction growth (VSRG) pathway, phase-segregated SnO2 nanorods (NRs, length 1-2 mu m and diameter 10-20 nm) were developed in a matrix of CaCl2 salt by reacting CaO particles with a flowing mixture of SnCl4 and Ar gases at elevated temperatures. The SnO2 NRs were investigated as a potential anode material for Li-ion batteries (LIBs). A half-cell constructed from the as-fabricated SnO2 electrode and a Li foil exhibited a reversible capacity 435 mA h g(-1) after one hundred cycles at a current density of 100 mA g(-1) (0.13 C). The SnO2 NRs exhibited much better Li storage properties, higher reversible capacity and cyclic capacity retention after extended cycling, than commercial SnO2 particles did. The improved electrochemical performance is attributed to the presence of an inactive amorphous byproduct matrix, which contains Li2O, the decomposed electrolyte, and the solid electrolyte interphase (SEI), among the reduced NRs. The matrix probably buffered and reduced the stress caused by the volume change of the electrode during the charge-discharge cyclings.