Browsing by Author "Tsai, WJ"

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A new synthetic approach for nonlinear optical chromophores possessing enhanced thermal stability
(1996-09-23)
Shu, CF
;
Tsai, WJ
;
Jen, AKY
;
應用化學系
;
Department of Applied Chemistry
A synthetic strategy for NLO chromophores containing cyclic-locked, conjugated triene segment has been developed. The incorporation of the ethylenic bonds into a 6-membered ring resulted in enhanced thermal stabilities of chromophores. Copyright (C) 1996 Elsevier Science Ltd
A new synthetic approach for nonlinear optical chromophores possessing enhanced thermal stability
(1996-09-23)
Shu, CF
;
Tsai, WJ
;
Jen, AKY
;
應用化學系
;
Department of Applied Chemistry
A synthetic strategy for NLO chromophores containing cyclic-locked, conjugated triene segment has been developed. The incorporation of the ethylenic bonds into a 6-membered ring resulted in enhanced thermal stabilities of chromophores. Copyright (C) 1996 Elsevier Science Ltd
A novel erase scheme to suppress overerasure in a scaled 2-bit nitride storage flash memory cell
(2004-09-01)
Yeh, CC
;
Wang, TH
;
Tsai, WJ
;
Lu, TC
;
Liao, YY
The cause of over-erasure in a two-bit nitride storage Flash memory cell is investigated. Extra positive charges accumulated above the n(+) unction and channel-shortening enhanced drain-induced barrier lowering effect are found to be responsible for threshold voltage (V-t) lowering in an over-erased cell. A modified erase scheme is proposed to resolve this issue. By applying a source voltage during erase, the erase speed can be well controlled for cells with different channel lengths and a wide range of program-state Vt distribution, which will reduce overerasure significantly.
A novel fully CMOS process compatible PREM for SOC applications
(2005-03-01)
Yeh, CC
;
Wang, TH
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Tsai, WJ
;
Lu, TC
;
Liao, YY
A novel nonvolatile memory cell named programmable resistor with eraseless memory (PREM) is proposed for system on chip applications for the first time. PREM combines a novel "eraseless" algorithm and the progressive breakdown of an ultrathin oxide. No or one extra mask is needed with a standard CMOS process. Multitime programming, multilevel cell, nonvolatility, and low-voltage operation are realized. Good reliability is demonstrated based on the result of a single cell.
A novel operation method to avoid overerasure in a scaled trapping-nitride localized charge storage flash memory cell and its application for multilevel programming
(2006-04-01)
Tsai, WJ
;
Zous, NK
;
Wang, TH
;
Ku, YHJ
;
Lu, CY
By using the charge pumping technique, it was found that the injected-hole occupied percentage increases with respect to the whole channel, and overerasure thus happens in a scaled trapping-nitride storage Flash memory cell. Such overerasure can be avoided or can be recovered if the cell is suitably biased during the erase operation. Moreover, the erase threshold voltage can be well controlled by the applied erase gate voltage. The reason is that both the channel-hot electrons and the band-to-band tunneling-induced hot holes would inject at the same time and are in balance as a specific surface potential is achieved. Based on this study, a self-limited soft program, as well as a self-saturated erase scheme, is proposed. Applications of this concept to multilevel programming are also demonstrated.
A novel PHINES flash memory cell with low power program/erase, small pitch, two-bits-per-cell for data storage applications
(2005-04-01)
Yeh, CC
;
Wang, TH
;
Tsai, WJ
;
Lu, TC
;
Chen, MS
A novel programming by hot-hole injection nitride electron storage (PHINES) Flash memory technology is-developed. The memory bit size of 0.046 mu m(2) is fabricated based on 0.13-mu m technology. PHINES cell uses a nitride trapping storage cell structure. Fowler-Nordheim (FN) injection is performed to raise V-t in erase while programming is done by lowering a local V-t through hand-to-hand tunneling-induced hot hole (BTBT HH) injection. Two-bits-per-cell feasibility, low-power and high-speed program/erase, good endurance and data retentivity make it a promising candidate for Flash EEPROM technology in gigabit era applications.
An endurance evaluation method for flash EEPROM
(2004-05-01)
Zous, NK
;
Chen, YJ
;
Chin, CY
;
Tsai, WJ
;
Lu, TC
Trap generation is hard to estimate in a Flash cell due to a dynamic stress field during program and erase. In this paper, a linear correlation is found between the erase state V-T rollup, and cycling V-T window. With the knowledge of the time dependence of erase stress field based on Fowler-Nordheim (FN) tunneling, the V-T rollup during cycling is evaluated by incorporating field dependent oxide trap generation. The extracted Delta V-T degradation slope during constant FN stress can be applied quantitatively to predict the V-T window closure during Flash cell cycling.
Buffer-sharing techniques in service-guaranteed video servers
(1999-09-01)
Tsai, WJ
;
Lee, SY
;
資訊工程學系
;
Department of Computer Science
Advances in networking and storage technology have made it possible to deliver on-demand services over networks such as the emerging video-on- demand (VOD) applications. Although a variety of studies have been focused on designing video servers suitable for VOD applications, the number of concurrent on-demand services supported by such servers is often limited by the I/O bandwidth of the storage systems. Recently, several researchers have focused on providing guaranteed services instead of on-demand services in a VOD system. A service is said to be guaranteed if every viewer can be served within a specified waiting time after the video has been subscribed. This paper describes a model called a buffer-sharing autonomy, which combines batching and bridging techniques to provide guaranteed services to VOD systems. We also describe how buffer-sharing techniques can be used in this model to provide the same services with fewer buffer resource through the use of playback-rate alteration. Additionally, in order to make buffer sharing efficient, it is important to group appropriate video streams together to share buffer resource. Four grouping policies are proposed for this purpose and the benefits yielded are also analyzed and compared. Finally, the results of our experiments show that the proposed buffer-sharing techniques promise the provision of guaranteed video services at low cost.
Dynamic buffer management for near video-on-demand systems
(1998-01-01)
Tsai, WJ
;
Lee, SY
;
資訊工程學系
;
Department of Computer Science
Advances in networking and storage technology have made it possible to deliver on-demand services over networks such as the emerging video-on-demand (VOD) applications. A variety of studies have been focused on designing a video server suitable for VOD applications. However, the number of concurrent on-demand services supported by the server is often limited by the I/O bandwidth of the storage systems. This paper describes a discrete buffer sharing model which uses batching and buffer sharing techniques in video servers to support a large number of VOD services. Two operations, splitting and merging, enable the model to fully utilize system resources such as buffers and disk bandwidths. Moreover, this paper also introduces the concept of imprecise video viewing which assumes that a limited amount of quality loss is acceptable during video playback. Based upon this assumption, three shrinking strategies are explored to reduce buffer requirements. Finally, the results of experiments show that our methods perform better than traditional buffer management techniques for VOD systems.
Enhancement of Subnikov-de Haas oscillations by microwave radiation
(1997-12-01)
Fan, JC
;
Chang, YH
;
Chen, YF
;
Whang, JF
;
Fang, FF
We report for the first time that the Subnikov-de Haas (SdH) pattern can be greatly enhanced by recording the changes in the quantum oscillations of magnetoresistance due to microwave radiation. In order to understand the origin of the enhancement, the dependence of the enhanced SdH signal on temperature, microwave frequency and power has been studied. It is concluded that the enhancement can be attributed to the effects of free carrier absorption and the suppression of the nonoscillatory magnetoresistance. The technique shown here can be used to detect the SdH oscillations at relatively high temperature and in samples with moderate mobilities without perturbing the carrier concentration.
Investigation of programmed charge lateral spread in a two-bit storage nitride flash memory cell by using a charge pumping technique
(2004)
Gu, SH
;
Wang, MT
;
Chan, CT
;
Zous, NK
;
Yeh, CC
The lateral distribution of programmed charge in a hot electron program/hot hole erase nitride storage flash cell is investigated by using a charge pumping technique. Our study shows that the secondly programmed bit has a wider trapped charge distribution than the first programmed bit. In addition, we find prograrnmed charge spreads further into the channel with program/erase cycle number.
Lateral migration of trapped holes in a nitride storage flash memory cell and its qualification methodology
(2004-09-01)
Zous, NK
;
Lee, MY
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Tsai, WJ
;
Kuo, A
;
Huang, LT
The negative threshold voltage (V-t) shift of a nitride storage flash memory cell in the erase state will result in an increase in leakage current. By utilizing a charge pumping method, we found that trapped hole lateral migration is responsible for this V-t shift. Hole transport in nitride is characterized by monitoring gate induced drain leakage current and using a thermionic emission model. The hole emission induced V-t shift shows a linear correlation with bake time in a semi-logarithm plot and its slope depends on the bake temperature. Based on the result, an accelerated qualification method for the negative V-t drift is proposed.
Multi-partition RAID: A new method for improving performance of disk arrays under failure
(1997)
Tsai, WJ
;
Lee, SY
;
交大名義發表
;
資訊科學與工程研究所
;
National Chiao Tung University
Disk arrays have been proposed as a way of improving I/O performance by using parallelism among multiple disks. This paper focuses, however, on improving the performance of disk array systems in the presence of disk failures, which are significant for applications where continuous operation is of concern. Although several approaches have been explored, the goals of achieving high performance and storage efficiency often conflict. In this paper, we propose a new variation of RAID organization, multi-partition RAID (mP-RAID), to improve storage efficiency and reduce performance degradation when disk failures occur. The idea is to recognize that frequently demanded data dominate the degree of the performance degradation when disk failures occur. mP-RAID subdivides a disk array into several partitions associated with different block organizations. Based upon data popularity, we assign data to appropriate partitions so that high performance and better storage efficiency can be achieved simultaneously.
Positive oxide charge-enhanced read disturb in a localized trapping storage flash memory cell
(2004-03-01)
Tsai, WJ
;
Yeh, CC
;
Zous, NK
;
Liu, CC
;
Cho, SK
Read disturb-induced erase-state threshold voltage instability in a localized trapping storage Flash memory cell with a poly-silicon-oxide-nitride-oxide-silicon (SONOS) structure is investigated and reported. Our results show that positive trapped charge in bottom oxide generated during program/erase (P/E) cycles play a major role. Both gate voltage and drain voltage will accelerate the threshold voltage (V-t) drift. Hot-carrier caused disturb effect is more severe in a shorter gate length device at low temperature. A model of positive charge-assisted electron tunneling into a trapping nitride is proposed. Influence of channel doping on the V-t drift is studied. As the cell is in an "unbiased" storage mode, tunnel detrapping of positive oxide charges is responsible for the threshold voltage shift, which is insensitive to temperature.
Synthesis of second-order nonlinear optical chromophores with enhanced thermal stability and nonlinearity: A conformation-locked trans-polyene approach
(1996-10-07)
Shu, CF
;
Tsai, WJ
;
Chen, JY
;
Jen, AKY
;
Zhang, Y
A facile synthesis that combines the use of an easily polarizable thiophene ring and a ring-locked triene as efficient conjugating moieties is employed to simultaneously enhance molecular nonlinearity (as high as 13 000 x 10(-48) esu) and thermal stability; incorporating this highly nonlinear chromophore in polyquinoline results in high electrooptic activity and long-term alignment stability at 100 degrees C for more than 1000 h.