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Formation of the distributed NiSiGe nanocrystals nonvolatile memory formed by rapidly annealing in N-2 and O-2 ambient
(2010-10-01)
Hu, Chih-Wei
;
Chang, Ting-Chang
;
Tu, Chun-Hao
;
Chiang, Cheng-Neng
;
Lin, Chao-Cheng
In this work, electrical characteristics of the Ge-incorporated Nickel silicide (NiSiGe) nanocrystals memory device formed by the rapidly thermal annealing in N-2 and O-2 ambient have been studied. The trapping layer was deposited by co-sputtering the NiSi2 and Ge, simultaneously. Transmission electron microscope results indicate that the NiSiGe nanocrystals were formed obviously in both the samples. The memory devices show obvious charge-storage ability under capacitance-voltage measurement. However, it is found that the NiSiGe nanocrystals device formed by annealing in N-2 ambient has smaller memory window and better retention characteristics than in O-2 ambient. Then, related material analyses were used to confirm that the oxidized Ge elements affect the charge-storage sites and the electrical performance of the NCs memory. (C) 2010 Elsevier B.V. All rights reserved.
Nitric Acid Oxidized ZrO2 as the Tunneling Oxide of Cobalt Silicide Nanocrystal Memory Devices
(2011-09-01)
Hu, Chih-Wei
;
Chang, Ting-Chang
;
Tu, Chun-Hao
;
Chen, Yang-Dong
;
Lin, Chao-Cheng
In this study, ZrO2 formed by the nitric acid oxidation method is proposed to be the tunneling oxide for nonvolatile memory device applications. The sputtered Zr thin film was oxidized by immersing in the nitric acid solution (HNO3:H2O = 1:10) for 60 s at room temperature. The quality of the formed ZrO2 was also extracted by the capacitance-voltage and current density-voltage measurements. Then, X-ray photoelectron spectroscopy has been used to confirm that the deposited Zr can be oxidized completely after the oxidation process. Moreover, a CoSi2 thin film was deposited on the nitric acid oxidized ZrO2 as the self-assembled layer of the memory device. After the device fabrication, the electrical and material characteristics of the CoSi2 nanocrystal memory devices have also been demonstrated and discussed.
Nitric Acid Oxidation of Si for the Tunneling Oxide Application on CoSi2 Nanocrystals Nonvolatile Memory
(2010-01-01)
Hu, Chih-Wei
;
Chang, Ting-Chang
;
Tu, Chun-Hao
;
Chen, Yang-Dong
;
Lin, Chao-Cheng
In this work, nitric acid oxidation was studied to fabricate the tunneling oxide of nanocrystal memory devices. SiO2 about 4 nm thick was formed through oxidizing the sputtered Si film by immersing in nitric acid solution (HNO3:H2O=1:10) for 60 s. After oxide formation, a rapid thermal annealing process set at 700 degrees C for 30 s was used to improve oxide quality. In addition, the formed SiO2 film was analyzed by X-ray photoelectron, capacitance-voltage, and current density-voltage measurements to study the process of the nitric acid oxidation. After the investigation of the nitric acid oxidized SiO2, a 6 nm thick cobalt silicide thin film was deposited and aggregated on the formed SiO2 layer as the charge-trapping layer. The cobalt silicide nanocrystal memory device showed an obvious memory effect and good reliability, which confirms that the nitric acid oxidation method has potential for memory application.
High Density Ni Nanocrystals Formed by Coevaporating Ni and SiO2 Pellets for the Nonvolatile Memory Device Application
(2010-01-01)
Hu, Chih-Wei
;
Chang, Ting-Chang
;
Tu, Chun-Hao
;
Huang, Yu-Hao
;
Lin, Chao-Cheng
We propose a method to fabricate a Ni nanocrystal structure by simultaneously coevaporating Ni and SiO2 pellets. An 800 degrees C rapid thermal annealing was used to enhance the Ni nanocrystals to aggregate. Transmission electron microscopy indicates that the formed Ni nanocrystals show a high density distribution of about 4.5x10(12) cm(-2). Then, the memory device using the Ni nanocrystals as charge-trapping centers was fabricated. The Ni nanocrystal memory device has an obvious memory window under capacitance-voltage measurement. X-ray photoelectron spectroscopy confirms the memory effect results from the Ni nanocrystals embedded in the SiO2 dielectric layer. Moreover, related reliability characteristics have been extracted.
Formation of the distributed NiSiGe nanocrystals nonvolatile memory formed by rapidly annealing in N(2) and O(2) ambient
(2010-10-01)
Hu, Chih-Wei
;
Chang, Ting-Chang
;
Tu, Chun-Hao
;
Chiang, Cheng-Neng
;
Lin, Chao-Cheng
In this work, electrical characteristics of the Ge-incorporated Nickel silicide (NiSiGe) nanocrystals memory device formed by the rapidly thermal annealing in N(2) and O(2) ambient have been studied. The trapping layer was deposited by co-sputtering the NiSi(2) and Ge, simultaneously. Transmission electron microscope results indicate that the NiSiGe nanocrystals were formed obviously in both the samples. The memory devices show obvious charge-storage ability under capacitance-voltage measurement. However, it is found that the NiSiGe nanocrystals device formed by annealing in N(2) ambient has smaller memory window and better retention characteristics than in O(2) ambient. Then, related material analyses were used to confirm that the oxidized Ge elements affect the charge-storage sites and the electrical performance of the NCs memory. (C) 2010 Elsevier B.V. All rights reserved.
Real-time investigation of the structural evolution of electrodes in a commercial lithium-ion battery containing a V-added LiFePO4 cathode using in-situ neutron powder diffraction
(2013-12-15)
Hu, Chih-Wei
;
Sharma, Neeraj
;
Chiang, Ching-Yu
;
Su, Hui-Chia
;
Peterson, Vanessa K.
In-situ neutron powder diffraction was employed to investigate the structural evolution of the electrode materials in a commercial lithium-ion battery used for electric buses in Taiwan. The battery, containing a vanadium-added LiFePO4 cathode, does not exhibit a delayed phase transition between LiFePO4 (triphylite) and FePO4 (heterosite) suggesting that the delayed phase transition can be suppressed through the use of vanadium-added LiFePO4 cathodes, which also enhances the capacity and prolongs the cycle life of these batteries. Furthermore, we characterize the readily reversible structural change of the anode (LixC6 where 0 < x <= 1) and correlate this to battery voltage. (C) 2013 Elsevier B.V. All rights reserved.
Vanadium Substitution of LiFePO4 Cathode Materials To Enhance the Capacity of LiFePO4-Based Lithium-Ion Batteries
(2012-11-22)
Chiang, Ching-Yu
;
Su, Hui-Chia
;
Wu, Pin-Jiun
;
Liu, Heng-Jui
;
Hu, Chih-Wei
The mechanism of enhancing the capacity of the LiFePO4 cathodes in lithium ion batteries by the addition of a small amount of vanadium, which locate on the lithium site and induce lithium vacancies in the crystal structure, is reported in this article. As a result, the capacity increases from 138 mAh/g found for pristine LiFePO4 to 155 mAh/g for the V-added compound, and the conductivity increases from 4.75 x 10(-4) S/cm for the LiFePO4 without V addition to 1.9 x 10(-2) S/cm for the V-added compound. A possible model to facilitate the enhancement of conductivity and capacity is described with evidence supported by X-ray powder diffraction, X-ray absorption spectroscopy, and neutron powder diffraction data.
Enhancing threshold voltage of AlGaN/GaN high electron mobility transistors by nano rod structure: From depletion mode to enhancement mode
(2012-09-10)
Xuan, Rong
;
Kuo, Wei-Hong
;
Hu, Chih-Wei
;
Lin, Suh-Fang
;
Chen, Jenn-Fang
This paper presents an approach in fabricating normally off AlGaN/GaN high electron mobility transistors (HEMTs). The fabrication technique was based on the carbon-doped GaN epitaxy layers on silicon substrate and the nano rod structure of the gate region in AlGaN/GaN HEMTs. Using this method, the threshold voltage of AlGaN/GaN HEMTs can be shifted from -2 V in a conventional depletion-mode (D-mode) AlGaN/GaN HEMT to 2 V in an enhancement-mode (E-mode) AlGaN/GaN HEMT. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4752113]
Nitric Acid Oxidized ZrO(2) as the Tunneling Oxide of Cobalt Silicide Nanocrystal Memory Devices
(2011-09-01)
Hu, Chih-Wei
;
Chang, Ting-Chang
;
Tu, Chun-Hao
;
Chen, Yang-Dong
;
Lin, Chao-Cheng
In this study, ZrO(2) formed by the nitric acid oxidation method is proposed to be the tunneling oxide for nonvolatile memory device applications. The sputtered Zr thin film was oxidized by immersing in the nitric acid solution (HNO(3):H(2)O = 1:10) for 60 s at room temperature. The quality of the formed ZrO(2) was also extracted by the capacitance-voltage and current density-voltage measurements. Then, X-ray photoelectron spectroscopy has been used to confirm that the deposited Zr can be oxidized completely after the oxidation process. Moreover, a CoSi(2) thin film was deposited on the nitric acid oxidized ZrO(2) as the self-assembled layer of the memory device. After the device fabrication, the electrical and material characteristics of the CoSi(2) nanocrystal memory devices have also been demonstrated and discussed.
A counter electrode based on hollow spherical particles of polyaniline for a dye-sensitized solar cell
(2012)
Huang, Kuan-Chieh
;
Hu, Chih-Wei
;
Tseng, Chen-Ya
;
Liu, Chen-Yu
;
Yeh, Min-Hsin
Hollow spherical polyaniline (hsPANI) particles are synthesized and deposited on an ITO/glass substrate to prepare a counter electrode (designated as hsPANI-CE) for a dye-sensitized solar cell (DSSC). The structure and crystallization of the hsPANI particles are characterized by using high resolution transmission electron microscopy (HR-TEM), field-emission scanning electron microscopy (FE-SEM), X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS), and Raman spectra. A power-conversion efficiency (h) of 6.84% is obtained for the DSSC with the hsPANI-CE, while it is 6.02% in the case of the DSSC with a CE based on pristine PANI (designated as PANI-CE). Such enhancement is attributed to the hsPANI film having a larger active surface area (A) of 0.191 cm(2), compared to that of the PANI film (A = 0.126 cm(2)), both values being estimated by a rotating disk electrode (RDE). Cyclic voltammetric (CV) curves have evidenced that the electro-catalytic ability of the hsPANI-CE for the reduction of tri-iodide (I-3(-)) ions is higher than that of the PANI-CE. As a reference, the DSSC with a Pt-sputtered CE gives an h of 7.17%. Electrochemical impedance spectroscopic (EIS) spectra are used to substantiate the photovoltaic behaviors. The results suggest that the film consisting of hsPANI particles can be a potential catalytic layer for the replacement of Pt in the CE of a DSSC.

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