Browsing by Author "Tseng, Po-Hao"

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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.
Conducting polymer blends prepared from polyaniline with n-dodecylbenzenesulfonic acid zinc salt as the secondary dopant
(2008-06-15)
Chao, Liang
;
Han, Yu-Kai
;
Hiseh, Bi-Zen
;
Huang, Ying-Jie
;
Hsieh, Tar-Hwa
A red-shift of the UV-vis spectra of n-dodecylbenzenesulfonic acid doped polyaniline (PANI (DBSA)(0.5)), resulting from the secondary doping of polyaniline backbones, was found in the presence of n-dodecylbenzenesulfonic acid zinc salt (Zn(DBS)(2)). It is proved to behave as steric hindrance spacers to induce the extension of the conjugation length through the straightening effect on the polyaniline backbones and the obtained mixtures (PANI(DBSA)(0.5) plus Zn(DBS)(2)) can be used as master batch materials (MB-13) for blending with regular polypropylene polymer (PP). The thermal degradation accompanied with loss of conductivity for MB-13 can be delayed to over 250 degrees C.when enough Zn(DBS)(2) was secondarily doped on PANI(DBSA)0.5., which allow the performance of its blending with other nonconducting/regular polymers possible. Below 80 rpm, increasing shear rates would induce higher viscosity difference between the MB-13 and PP matrix, resulting in elongation of MB-13 in the PP matrix and higher conductivities of the polyblends. The deviation from the Taylor equation, which is used to estimate the degree of elongation for a polyblend, started when shear rate is over 80 rpm. The leakage of Zn(DBS)(2) out of MB-13 can be confirmed by comparing the DSC thermograms and X-ray diffraction patterns with that of neat PP. Gradual deformation for the conductive fillers (MB-13) and a well-defined and expanded layered structure can be found when processing time is below 15 min with 60 rpm shear rate. The layers started to shrink back after 15 min of procession with the loss of the Zn(DBS)(2) from MB-13 in the PP matrix. (c) 2008 Wiley Periodicals, Inc.
Degradation induced variation of LC transition of poly(n-undecyl isocyanate)
(2008-05-01)
Hsieh, Bi-Zen
;
Chuang, Hung-Yi
;
Chao, Liang
;
Huang, Ying-Jie
;
Tseng, Po-Hao
The first-order thermal transitions including side-chain melting, crystal-LC, biphasic chimney-like, and isotropic transitions of poly(n-undecyl isocyanate) (PUDIC) were investigated by varying its thermal history. After annealing at 140 degrees C for different periods of time, it leads to different degrees of backbiting degradation into n-undecyl isocyanurate trimer which behaves as a solvent for the rest non-degraded/rigid PUDIC to change into a lyotropic LC from thermotropic transition. Based on the degree of degradation, various amounts of trimers are present and the PUDIC demonstrates different types of thermal transitions found in DSC thermograms due to the variation of the non-degraded PUDIC concentration in solvent trimers. Finally, a phase diagram includes all types of crystallines, LC, and isotropic regions can be drawn according to the DSC thermograms. (C) 2008 Elsevier Ltd. All rights reserved.
Formation mechanism of a nanotubular polyanilines prepared by an emulsion polymerization without organic solvent
(2008-09-09)
Hsieh, Bi-Zen
;
Chuang, Hung-Yi
;
Chao, Liang
;
Li, Yu-Jen
;
Huang, Ying-Jie
A nanotubular polyaniline (PANINT) was prepared from a simple emulsified polymerization method without oil solvent present. A mechanism of the formation of the nano-fibers/tubes was proposed to show that it started with the connecting arrangement of the neighboring anilinium micelles before and during polymerization, which resulted in the formation of the intermediate morphology of centipedes converting into rod-like nanofibers later. The obtained PANINTs displayed not only nanofibrous structure but owned an unusual dispersing behavior in toluene. SEM and TEM showed the dendrite-like networks of nanofibers connected and glued together by the free (not complexed to polyaniline backbone) n-dodecylbenzene sulfonic acid (DBSA) molecules. After removing the free DBSA by acetone, the clear/well-defined empty nanotubes can be seen from TEM in the magnified micrograph. The Atomic force microscopic (AFM) microgaphs demonstrated the cottage like surface morphology of the un-perturbed PANINTs and the morphology was converted to an anisotropic/oriented rods after rubbing on the wet/ cast PANINTs' dispersion of toluene before entire evaporation. (c) 2008 Published by Elsevier Ltd.
Shearing effects on the conducting polymer blends
(2008-06-01)
Chao, Liang
;
Huang, Ying-Jie
;
Han, Yu-Kai
;
Tseng, Po-Hao
;
Hsieh, Tar-Hwa
To obtain a highly conductive polyblend based on doped polyaniline, an zinc salt based conductive master batch material (MB-13) made from mixing zinc n-dodecylbenzene sulfonate (Zn (DBS)(2)) and n-dodecylbenzene sulfonic acid (HDBSA) polyaniline (PANI(DBSA)(0.5)) together was compounded with PP in a melt-mixer varying the processing conditions. The SEM pictures show the morphologies of the polyblends were phase-separated into strips of elongated MB-13 for all samples. The elongation was first enhanced at shear rates ranged from 20 to 60 rpm. A shear rate of 60 rpm at 180 degrees C can elongate the conductive master batch phases (filler) to obtain both the highest aspect ratio and least resistance by keeping the secondary dopants of Zn (DBS)(2) stay within MB-13 from losing its conductivity and deformability.