Browsing by Author "Lu, Chia-Yu"

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DC and AC NBTI stresses in pMOSFETs with PE-SiN capping
(2006)
Lu, Chia-Yu
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Lin, Horng-Chih
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Chang, Yi-Feng
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Huang, Tiao-Yuan
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電子工程學系及電子研究所
Impacts of low-pressure chemical vapor deposition-SiN capping layer and lateral distribution of interface traps on hot-carrier stress of n-channel metal-oxide-semiconductor field-effect-transistors
(2007-04-01)
Lu, Ching-Sen
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Lin, Horng-Chih
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Huang, Jian-Ming
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Lu, Chia-Yu
;
Lee, Yao-Jen
The characteristics of n-channel metal-oxide-semiconductor field-effect transistors (NMOSFETs) with a SiN capping layer were investigated in this study. Although the incorporation of the SiN capping layer markedly enhanced the carrier mobility and thus the drive current of the fabricated devices, the resistance to hot-carrier degradation was sacrificed, owing to the high content of hydrogen in the SiN layer that might diffuse to the channel region during the process. Even if the SiN layer was removed and the channel strain was released later, the hot-carrier degradation was severer than that in devices without SiN capping. Finally, the lateral distribution of generated interface states due to hot-carrier stress was also investigated in this study.
Impacts of SiN-capping layer on the device characteristics and hot-carrier degradation of nMOSFETs
(2007-03-01)
Lu, Chia-Yu
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Lin, Horng-Chih
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Lee, Yao-Jen
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Shie, Yu-Lin
;
Chao, Chih-Cheng
Im pacts of silicon nitride (SiN)-capping layer and the associated deposition process on the device characteristics and hot-electron degradation of nMOSFETs are investigated in this paper. The SiN layer used to induce channel strain for mobility enhancement was deposited by a low-pressure chemical vapor deposition. The deposition of the SiN aggravates threshold-voltage roll-off due to additional thermal budget and the strain effect. It is also found that the device hot-electron degradation is worse with the addition of the SiN capping. Furthermore, our results indicate that both the bandgap narrowing caused by the channel strain and the abundant hydrogen species from the precursors of SiN deposition contribute to the aggravated hot-electron effect.
Purification, crystallization and preliminary X-ray crystallographic analysis of glycosyltransferase-1 from Bacillus cereus
(2014-09-01)
Hsieh, Yin-Cheng
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Chiu, Hsi-Ho
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Huang, Yen-Chieh
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Fun, Hoong-Kun
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Lu, Chia-Yu
Glycosyltransferases (GTs), which are distributed widely in various organisms, including bacteria, fungi, plants and animals, play a role in synthesizing biological compounds. Glycosyltransferase-1 from Bacillus cereus (BcGT-1), which is capable of transferring glucose to small molecules such as kaempferol and quercetin, has been identified as a member of the family 1 glycosyltransferases which utilize uridine diphosphate glucose (UDP-glucose) as the sugar donor. BcGT-1 (molecular mass 45.5 kDa) has been overexpressed, purified and crystallized using the hanging-drop vapour-diffusion method. According to X-ray diffraction of BcGT-1 crystals to 2.10 angstrom resolution, the crystal belonged to space group P1, with unit-cell parameters a = 54.56, b = 84.81, c = 100.12 A, alpha = 78.36, beta = 84.66, gamma = 84.84 degrees. Preliminary analysis indicates the presence of four BcGT-1 molecules in the asymmetric unit with a solvent content of 50.27%.
Three important amino acids control the regioselectivity of flavonoid glucosidation in glycosyltransferase-1 from Bacillus cereus
(2016-10)
Chiu, Hsi-Ho
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Hsieh, Yin-Cheng
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Chen, Ya-Huei
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Wang, Hsin-Ying
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Lu, Chia-Yu
Glycosyltransferase-1 from Bacillus cereus (BcGT1) catalyzes a reaction that transfers a glucosyl moiety to flavonoids, such as quercetin, kaempferol, and myricetin. The enzymatic glucosidation shows a broad substrate specificity when the reaction is catalyzed by wild-type BcGT1. Preliminary assays demonstrated that the F240A mutant significantly improves the regioselectivity of enzymatic glucosidation toward quercetin. To unveil and further to control the catalytic function of BcGT1, mutation of F240 to other amino acids, such as C, E, G, R, Y, W, and K, was performed. Among these mutants, F240A, F240G, F240R, and F240K greatly altered the regioselectivity. The quercetin-3-O-glucoside, instead of quercetin-7-O-glucoside as for the wild-type enzyme, was obtained as the major product. Among these mutants, F240R showed nearly 100 % product specificity but only retained 25 % catalytic efficiency of wild-type enzyme. From an inspection of the protein structure, we found two other amino acids, F132 and F138, together with F240, are likely to form a hydrophobic binding region, which is sufficiently spacious to accommodate substrates with varied aromatic moieties. Through the replacement of a phenylalanine by a tyrosine residue in the substrate-binding region, the mutants may be able to fix the orientation of flavonoids, presumably through the formation of a hydrogen bond between substrates and mutants. Multiple mutants-F240R_F132Y, F240R_F138Y, and F240R_F132Y_F138Y-were thus constructed for further investigation. The multiple points of mutants not only maintained the high product specificity but also significantly improved the catalytic efficiency, relative to F240R. The same product specificity was obtained when kaempferol and myricetin were used as a substrate.