Browsing by Author "Ho, Tsung-Han"

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Formation and degradation mechanism of a novel nanofibrous polyaniline
(2009-06-01)
Ho, Ko-Shan
;
Han, Yu-Kai
;
Tuan, Yu-Tsung
;
Huang, Ying-Jie
;
Wang, Yen-Zen
A nanotubular, nanofibrous polyaniline (PANINT) was prepared from an emulsion polymerization in the presence of n-dodecylbenzene sulfonic (DBSA) and hydrochloric acids. The building of the tubular structure based on the tubular micelles from the accumulation (pile up) of micelles at high surfactant concentration, leading to early stage of centipede-like and eventual tubular morphologies. The PANINT molecule owning a highly conjugated backbone demonstrated a free carrier-tail in the near-IR region due to its helical conformation. After dedoping, the once empty PANINT with only some complexed DBSA inside shrank into solid rods, after the removal of the complexed DBSA. As a result, the solid rods were filled with helical emeradine base (nano-EB) molecules associated with inter-molecular H-bonding. The solid rods of nano-EB went on crosslinking and carbonization after 200-300 degrees C by opening the quinoid rings and the inter-molecular H-bondings were destroyed with nano-EB molecules crosslinking into ladder-like structure. When temperature was over 300 degrees C and below 800 degrees C, carbonization enhanced by de-ammoniaization, causing a significant weight loss. However, the cleavage of aromatic rings into aliphatic pieces occurred after 800 degrees C, which chopped the ladder-like, strips of carbonized nano-EB sheets into small pieces of nano-particles. The conductivity of the pyrolyzed nano-EB was found to be around 10(-5) s/cm, 10,000 times higher than the neat nano-EB of 10(-9) s/cm due to the carbonization. (C) 2009 Elsevier B.V. All rights reserved.
Unipolar resistive switching behaviors and mechanisms in an annealed Ni/ZrO2/TaN memory device
(2015-01-28)
Tsai, Tsung-Ling
;
Ho, Tsung-Han
;
Tseng, Tseung-Yuen
;
電子物理學系
;
Department of Electrophysics
The effects of Ni/ZrO2/TaN resistive switching memory devices without and with a 400 degrees C annealing process on switching properties are investigated. The devices exhibit unipolar resistive switching behaviors with low set and reset voltages because of a large amount of Ni diffusion with no reaction with ZrO2 after the annealing process, which is confirmed by ToF-SIMS and XPS analyses. A physical model based on a Ni filament is constructed to explain such phenomena. The device that undergoes the 400 degrees C annealing process exhibits an excellent endurance of more than 1.5 x 10(4) cycles. The improvement can be attributed to the enhancement of oxygen ion migration along grain boundaries, which result in less oxygen ion consumption during the reset process. The device also performs good retention up to 10(5) s at 150 degrees C. Therefore, it has great potential for high-density nonvolatile memory applications.