Browsing by Author "Lee, C. W."

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Chip-Level Characterization and RTN-Induced Error Mitigation beyond 20nm Floating Gate Flash Memory
(2018-01-01)
Lin, T. W.
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Ku, S. H.
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Cheng, C. H.
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Lee, C. W.
;
Ijen-Huang
Vt instability caused by random telegraph noise (RTN) in floating gate flash memories beyond 20nm is studied comprehensively. Experiments reveal that the RTN would cause Vt distribution with a kinked tail which re-distributes to a "Gaussian-like" shape rapidly and was measured by the self established Budget Product Tester (BPT). A Multi-Times Verify (MTV) algorithm to mitigate the statistical tail, thus enlarging operation window is also exhibited by BPT. In further, a probability model to portray the compact Vt distribution under MTV is proposed. Finally, the impact of MTV on lowering the requirement of Error-correcting code (ECC) bit is also demonstrated.
Erosion effects assessed by repeated gravity measurements in southern Taiwan
(2013-01-01)
Mouyen, M.
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Masson, F.
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Hwang, C.
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Cheng, C. -C.
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Le Moigne, N.
We analyse temporal variations of gravity measured in southern Taiwan since November 2006 at 10 sites using absolute gravimeters and, since November 2008, at 70 sites using a relative gravimeter. We describe and apply methods to interpret the gravity changes in terms of local hydrological processes and vertical ground motions. The effect of land water is computed from local rainfall data and a model of rain accumulation and discharge in the ground. The effect of the vertical motions of the ground is estimated using time-series of permanent Global Positioning System (GPS) stations and the theoretical gravity to height ratio of -2 mu Gal cm(-1). Unexpectedly, Morakot typhoon (2009 August), the strongest typhoon in Taiwan in 50 yr, was responsible for the highest gravity changes. Morakot triggered numerous large landslides and debris flow deposits. Their thicknesses are estimated from the gravity changes (up to similar to 280 mu Gal) along with field observations and satellite images.
Error Characterization and ECC Usage Relaxation beyond 20nm Floating Gate NAND Flash Memory
(2018-01-01)
Ku, S. H.
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Lin, T. W.
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Cheng, C. H.
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Lee, C. W.
;
Chen, Ti-Wen
Endurance of floating gate flash memories at 19nm node and beyond is studied comprehensively. Experiments reveal that the random telegraph noise (RTN) would degrade the read margin with a tail, which quickly reshapes into a symmetric Gaussian form in a lightly-stressed state. After heavy stress, the lower part of tail would spread further while the upper part keeps roughly overlapped with that during fresh. This unique behavior, which was firstly measured by the self-established Budget Product Tester (BPT), can be explained by stress-induced hole trap creation. To investigate the impact of RTN on operation window, a novel algorithm of Multi-Times-Verify accompanied with the optimal Read-Retry (MTVR2) is proposed and validated by BPT. The advantage of MTVR2 to reduce the requirement of Error-Correcting Code (ECC) bit is demonstrated. Finally, the improvement of bit error rate (BER) in TLC operation with MTVR(2 )is also evaluated.
Expected temporal absolute gravity change across the Taiwanese Orogen, a modeling approach
(2009-12-01)
Mouyen, M.
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Masson, F.
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Hwang, C.
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Cheng, C. -C.
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Cattin, R.
The island of Taiwan is located on the convergent boundary between the Philippine Sea plate and the Chinese continental margin. It offers very active mountain building and collapsing processes well illustrated by the rugged topography, rapid uplift and denudation, young tectonic landforms, active faulting and numerous earthquakes. In this paper, using simple models, we have estimated vertical movements and associated absolute gravity variations which can be expected along a profile crossing the southern part of the island and probably suffering the highest rates of rising. The two different tectonic styles proposed for the island, thin-skinned and thick-skinned, were taken into account. Horizontal and vertical movements were modeled by an elastic deformation code. Gravity variations due to these deformations are then modeled at a second step. They are dominated by plate and free-air effects, i.e. elevation of the topography, with several mu Gal yr(-1). By comparison, gravity changes generated by mass transfers are weak: maximum 0.1 mu Gal yr(-1) with the thin-skinned tectonic and 0.3 mu Gal yr(-1) with the thick-skinned tectonic. Though elastic rheology has limitations, this modeling offers interesting results on what gravity signal can be expected from the AGTO project (Absolute Gravity in the Taiwanese Orogen), which proposes to study the dynamic of these mountain ranges using absolute gravimetry (AG) and also including relative gravimetry (RG) and GPS measurements. (C) 2009 Elsevier Ltd. All rights reserved.
Green emitting polyhedral oligomeric silsesquioxanes/poly(phenylene vinylene) derivative materials for highly efficient organic light emitting diodes (OLEDs)
(2008-06-01)
Lee, C. W.
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Josse, Y.
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Hsu, C. H.
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Nguyen, T. P.
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應用化學系
Hybrid materials composed of polyhedral oligomeric silsesquioxanes (POSS) and a polyphenylene vinylene (PPV) derivative were fabricated and characterized by optical and surface spectroscopy. The hybrid thin films have similar optical properties as the pristine polymer but contributions of the POSS are evidenced in infrared spectroscopy. Organic light emitting diodes using the hybrid material as an emitter clearly showed an improvement of the electrical characteristics and the efficiency of the devices as compared to those using the pristine polymer. The effects of POSS incorporation to the polymer are discussed via the obtained results.
Hybrid nanocomposites for optical applications
(2009-10-01)
Nguyen, T. P.
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Lee, C. W.
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Hassen, S.
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Le, H. C.
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應用化學系
Incorporating inorganic particles into conjugated polymer matrices is an area of current interest in the fields of optoelectronics and solar energy. The hybrid nanocomposites exhibit interesting physical properties thanks to good optical properties of polymers and to high carrier mobility of inorganic semiconductors. A judicious combination of organic/inorganic can therefore provide materials of low cost, ease processing, high stability, with specific electrical and optical properties. In the present study, we briefly review the composite materials that have been successfully utilized in the field of optoelectronics and photovoltaic conversion. We shall describe in particular a family of nanocomposites using polyhedral oligomeric silsesquioxanes (POSS) of general formula (RSiO(3/2))(n) where R is an organic group as a core. The composites are made by grafting functional polymer groups to the core, which allows the control of their optical properties. Such composites have high mechanical resistance and stability because of the special structure of the core. For illustration, we present a study of polyfluorene (PF)/POSS materials used as an active layer in organic light emitting diodes, with improved performance as compared to those using polymer only, and we discuss the role of the particles in the transport and emission processes in the devices studied. (C) 2009 Elsevier Masson SAS. All rights reserved.
Investigations of organic light emitting diodes with CdSe(ZnS) quantum dots
(2008-02-15)
Lee, C. W.
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Chou, C. H.
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Huang, J. H.
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Hsu, C. S.
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Nguyen, T. P.
In this study, we report results on investigation of bilayer light emitting diodes made of organic capped CdSe(ZnS) core/shell type nanocrystals and poly [2-phenyl-3-(9,9-dihexyl-fluoren-2-yl) phenylene vinylene]-co-[2-methoxy-5-(2'-ethylhexyloxy) phenylene vinylene] (FP-PPV-co-MEH-PPV) electroluminescent co-polymer. Light emitting diodes of structure: indium-tin-oxide (ITO)/polyethylene dioxythiophene: polystyrene sulfonate (PEDOT:PSS)/FP-PPV-co-MEH-PPV/Ca/Al devices have been fabricated and studied. The co-polymer device emits a yellow light with a maximum brightness of 3949 cd/m(2) and a maximum external quantum efficiency of 0.27 cd/A at 10 V. Incorporation of CdSe(ZnS) quantum dots into the active polymer film resulted in an increase in device brightness, which reached 8192 cd/m(2) and in external quantum efficiency, which became 1.27 cd/A at 7 V with a lower turn-on voltage. The results indicate that CdSe(ZnS) quantum dots improved significantly the emission of the devices by modifying the injection and transport of the charge carriers. We suggest a non-uniform dispersion of QDs in the co-polymer layer with carrier blocking process by the particles, which produced a balanced charge distribution inside the co-polymer, and thus increased the emission efficiency. (c) 2007 Elsevier B.V. All rights reserved.
Study of trap states in polyfluorene based devices by using TSC technique
(2008-08-30)
Renaud, C.
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Huang, C. H.
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Lee, C. W.
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Le Rendu, P.
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Nguyen, T. P.
The trap states in poly(9,9-dihexylfluorene-co-N,N-di(9,9-dihexyl-2-fluorenyl)-N-phenylamine) (PF-N-Ph) based light emitting diodes have been investigated by using the thermally stimulated current (TSC) technique in the temperature range of 90-320 K. The studied structure consisted of indium-tin-oxide/polyethylene-dioxythiophene: polystyrene-sulfonate/PF-N-Ph/Al. Four traps centers denoted as A, B, C, and D trap types have been identified with densities in the range of 10(16)-10(17) cm(-3). Study of the dependence of TSC characteristics on the device polarity suggested that the A, C and D type traps are electron traps while the B type traps are hole traps. They can be described by Gaussian distributions centered on mean trap levels. (c) 2008 Elsevier B.V. All rights reserved.
Temperature dependence of the electric and spintronic transport properties of Germanium on glass
(2017-10-15)
Chen, C. H.
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Lee, C. W.
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Yu, Y. C.
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Lee, C. P.
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電子工程學系及電子研究所
We present electrical spin injection and detection in p-type Ge channels using Ni/Al2O3/Ge on glass tunneling contacts. The entire structure is integrated on a glass substrate. We investigate the temperature dependence of the Hanle effect in a composite p-type Ge on glass (GeOG), using three-terminal configuration Hanle measurements; from these measurements, we observe spin accumulation up to room temperature. A spin signal of 0.3 V and a spin lifetime of 34 ps are obtained at room temperature. (C) 2017 Elsevier B.V. All rights reserved.