Browsing by Author "Huang, WJ"

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AIGaN Schottky characteristics after hybrid photo-enhanced wet and inductively coupled plasma etch
(2001)
Huang, WJ
;
Fang, CY
;
Wong, JS
;
Lee, CS
;
Chang, EY
AlGaN Schottky contact characteristics after hybrid photo-enhanced wet etch and Inductively coupled plasma etch (ICP) is studied. AlGaN was grown by MOCVD on sapphire substrate. KOH solution and 100mW/cm(2) UV illumination by Hg are lamp was used for photo-enhanced wet etch. Gas mixture of Cl-2 and N-2 was used for ICP etch. The Schottky metal used in this study is Ni/Au (100nm/100nm) and the Ohmic metal used is Al (100nm). Typical etch rates are 0.28nm/min and 265nm/min with a roughness of 0.6nm and 1.17nm for wet and dry etch respectively. The ICP process etches more rapidly but the etched surfaces are rougher when compared to the wet-etch process. After ICP etch at 600 watt for 60sec, the schottky diode has an ideality factor n=2.6, and the barrier height phi(B)=0.65 eV However, for the ICP etched sample followed by photo-enhanced wet chemical etch for 30mins, the sample has an ideality factor n=0.99, and the barrier height phi(B)=0.86 eV, and the breakdown voltage is recovered from 4V to 7.5V The study indicates that the wet chemical etch can remove the damage caused by ICP etching. Overall, the hybrid dry/wet etch process is a high etch rate process and cause very low damages on the etched surface.
Conformational conversion and chain ordering in cycle olefin copolymer (COC)
(2000-01-01)
Chu, PP
;
Huang, WJ
;
Chang, FC
;
Fan, SY
;
應用化學系
Polynorbornene (PNB) or cycle olefin copolymer (COC) can undergo conformational conversion into the more stable T(T)G conformer from T(T)T and G(T)G. The conversion constitutes the nascent stage for the reordering process of the COG. Interconversion between two major chain conformers leads to two groups of C-13 NMR resonances corresponding to the CH carbon in the norbornene chain at 53 ppm (T(T)T + G(T)G) and 49 ppm (T(T)G). Chain reordering following the conversion leads to the condensation of the COC bulk and raises its T-g, substantially. The presence of random PE segment not only improves its segmental motion but also facilitates the conversion into the most stable T(T)G conformation. (C) 1999 Elsevier Science Ltd. Ail rights reserved.
Conformational conversion and local packing of cyclic olefin copolymers
(2000-12-12)
Chu, PPJ
;
Cheng, MH
;
Huang, WJ
;
Chang, FC
;
應用化學系
Cyclic olefin copolymer (COC, poly(norbornene-co-ethylene)) catalyzed by ansa-ethylenebis-(indenyl)zirconium dichloride (Et[Ind](2)ZrCl2)/methylaluminoxane (MAO) gives rise to phenomenal increase of T-g upon annealing. Unaveraged solid-state C-13 NMR resonance of the CH carbons in the norbornene (53 and 49 ppm) evidenced the conformation conversion from T[X]T and G[M]G to more stable T[X]G conformers (where [X] = [T] or [G] represent the norbornene chain conformation). As the persistent length increases with the conversion, local packing of the rigid chain subsequently occurs. Synchrotron source X-ray diffraction provides clear evidence of the averaged interchain contraction from 12.0 to 8.5 Angstrom and a tighter distribution in the spacing after annealing. In the preannealed state, T-1p(H) relaxation time revealed both mobile (where conformer converts) and rigid components (where conformation is frozen), which coalesce into a further rigid component after extended annealing. The mechanisms governing the packing in amorphous COC are likely by the random chain diffusion and not from cooperative motion as described by the bundle-packing model.
Copolymerization of norbornene with ethylene: a high-resolution liquid NMR, DSC and solid state NMR study
(2000-03-01)
Huang, WJ
;
Chang, FC
;
Chu, PPJ
;
應用化學系
;
Department of Applied Chemistry
In this paper, we report the monomer reactivity on the copolymerization of norbornene and ethylene. The reactivity ratios for ethylene (M-1) and norbornene (M-2) are 18.5 and 0.035, respectively. Different copolymerization conditions can produce COC with different microstructures. A C-13 NMR shift assignment in pentad sequences in copolymers has been obtained. More isolated polynorbornene or a micro-block length can be obtained using a low Zr/Al catalyst/co-catalyst ratio and at a lower NB/ethylene feed ratio. The T-1p(C) decay curve shows two component decays in all resonance peaks. These two component decays come from different norbornene microstructures, while the block and alternative have similar T-1p(C) values.
Effects of channel width and NH3 plasma passivation on electrical characteristics of polysilicon thin-film transistors by pattern-dependent metal-induced lateral crystallization
(2005)
Wu, YC
;
Chang, TC
;
Chou, CW
;
Wu, YC
;
Liu, PT
This work studied the effects of channel width and NH3 plasma passivation on the electrical characteristics of a series of pattern-dependent metal-induced lateral crystallization (PDMILC) polysilicon thin-film transistors (poly-Si TFTs). The performance of PDMILC TFTs improves as each channel width decreasing. Further, PDMILC TFTs with NH3 plasma passivation outperforms without such passivation, resulting from the effective hydrogen passivation of the grain-boundary dangling bonds, and the pile-up of nitrogen at the SiO2/poly-Si interface. In particular, the electrical characteristics of a nanoscale TFT with ten 67 nm wide split channels (M10) are superior to those of other TFTs. The former includes a higher field effect mobility of 84.63 cm(2)/V s, a higher ON/OFF current ratio (> 10(6)), a steeper subthreshold slope (SS) of 230 mV/decade, and an absence of drain-induced barrier lowering (DIBL). These findings originate from the fact that the active channels of the M10 TFT have exhibit the most poly-Si grain enhanced to reduce the grain boundary defects and the best NH3 plasma passivation. Both effects can reduce the number of defects at grain boundaries of poly-Si in active regions for high performances. (c) 2005 The Electrochemical Society. All rights reserved.
Etching damages on AlGaN, GaN and InGaN caused by hybrid inductively coupled plasma etch and photoenhanced chemical wet etch by Schottky contact characterizations
(2003-07-01)
Fang, CY
;
Huang, WJ
;
Chang, EY
;
Lin, CF
;
Feng, MS
The surface damaging effects of the inductively coupled plasma (ICP) etch and the photoenhanced chemical (PEC) wet etch on AlGaN, GaN and InGaN were systematically investigated. The surface morphologies and the etch rates after ICP etch and PEC wet etch were explored to achieve optimum conditions for a hybrid etch technique. The etch rates increased with the ICP power or concentration of KOH(aq) and the surface roughness was less after PEC wet etch than it was after ICP etch. Schottky characterizations of GaN and AlGaN diodes after pure ICP etch, pure PEC etch and hybrid ICP/PEC etch were investigated to elucidate the damaging effects on the surfaces. It shows that the PEC etch is an effective way to achieve a damage-free surface for GaN-based materials, and the hybrid ICP/PEC etch can be used for applications which require high etch rate and damage-free surfaces.
Fabrication and field emission characteristics of highly ordered titanium oxide nanodot arrays
(2005)
Chen, PL
;
Huang, WJ
;
Chang, JK
;
Kuo, CT
;
Pan, FM
A field emission triode device has been fabricated using self-organized nanodot arrays as the electron emission source. Uniform nanodot arrays of titanium oxide were prepared from the Al/Ti film stack on silicon substrates by electrochemical anodization. The field emission triodes with titanium oxide nanodot emitters exhibited a low gate turn-on voltage of 45 V and high emission current density of 25 mA/cm(2) at 120 V. The excellent electric properties and easily controllable fabrication process of the nanodot triodes show potential applications for field emission displays and vacuum microelectronics. (c) 2005 The Electrochemical Society.
Functionalization and chemical modification of cyclo olefin copolymers (COC)
(2000-07-01)
Huang, WJ
;
Chang, FC
;
Chu, PPJ
;
應用化學系
;
Department of Applied Chemistry
In this paper, we report two simple and effective bromination methods to brominate the cycle olefin copolymer (COC). A suitable metallic catalyst can accomplish functionalization and chromophorization of the brominated COG. A 2nd NLO dye, Disperse Orange 3(DO3) containing the -NH2 functional group, has been grafted onto either the norbornene unit or the PE segment of the COC backbone successfully, by the palladium catalyst, Pd-2(dba)(2)(Bis[dibenzylideneacetone] dipalladium). The observed low dye grafting content can be attributed to the higher hindrance of the norbornene ring. Based on UV results, the NLO-COC, having dye grafted onto the norbornene unit shows more red shift than that grafted onto the PE unit, probably due to greater shielding on the chromorphor. (C) 2000 Elsevier Science Ltd. All rights reserved.
Homopolymerization and copolymerization of tert-butyl methacrylate and norbornene with nickel-based methylaluminoxane catalysts
(2004-05-05)
Huang, CF
;
Wang, SK
;
Kuo, SW
;
Huang, WJ
;
Chang, FC
The homopolymerization and copolymerization of tert-butyl methacrylate (tBMA) and norbornene (NB) with nickel(II) acetylacetonate in combination with methylaluminoxane were systematically investigated. This catalytic system showed high activity toward the homopolymerization of both NB and tBMA. For these copolymerizations, activity was gradually lost with an addition of tBMA to NB or of NB to tBMA. This result was qualitatively explained with the trigger coordination mechanism. Furthermore, the determination of the reactivity ratios indicated a significantly whigher reactivity for NB than for tBMA (r(NB) = 4.14 and r(tBMA) = 0.097), and this was interpreted by the coordination mechanism. The synthesized acrylate/NB copolymers exhibited glass-transition temperatures of 100-250degreesC. The absence of crystallinity and the homogeneous repartition of the monomer units along the main chain yielded products with high transparency and high stability. (C) 2004 Wiley Periodicals, Inc.
Hydrogen bonding interactions and miscibility between phenolic resin and octa(acetoxystyryl) polyhedral oligomeric silsesquioxane (AS-POSS) nanocomposites
(2006-02-15)
Kuo, SW
;
Lin, HC
;
Huang, WJ
;
Huang, CF
;
Chang, FC
We have synthesized a polyhedral oligomeric silisesquioxane (POSS) derivative containing eight acetoxystyryl functional groups [octa(acetoxystyryl)octasilsesquioxane (AS-POSS)] and then blended it with phenolic resin to form nanocomposites stabilized through hydrogen bonding interactions between the phenolic resin's hydroxyl group and the AS-POSS derivative's carbonyl and siloxane groups. One-and two-dimensional infrared spectroscopy analyses provided positive evidence for these types of hydrogen bonding interactions. In addition, we calculated the interassociation equilibrium constant, based on the Painter-Coleman association model (PCAM), between phenolic resin and POSS indirectly from the fraction of hydrogen-bonded carbonyl groups; quantitative analyses indicate that the hydroxyl-siloxane interassociation from the PCAM is entirely consistent with the classical Coggesthall and Saier (C and S) methodology. From a thermal analysis, we observed that the miscibility between phenolic and AS-POSS occurs at a relatively low AS-POSS content, which characterizes this mixture as a polymer nanocomposite system. (c) 2006 Wiley Periodicals, Inc.
Influence of PMMA-chain-end tethered polyhedral oligomeric silsesquioxanes on the miscibility and specific interaction with phenolic blends
(2006-01-10)
Huang, CF
;
Kuo, SW
;
Lin, FJ
;
Huang, WJ
;
Wang, CF
Two different molecular weights of poly(methyl methacrylate) (PMMA) and PMMA containing polyhedral oligomeric silsesquioxane (PMMA-POSS) homopolymers have been prepared via the atom transfer radical polymerization (ATRP) technique. The miscibility and specific interaction behaviors of PMMA-POSS and PMMA with phenolic resin were investigated by differential scanning calorimetry and Fourier transform infrared spectroscopy (FTIR). FTIR results reveal that at least three competing equilibriums are present in the phenolic/PMMA-POSS blend: self-association of phenolic (hydroxyl-hydroxyl), hydroxyl-siloxane interassociation between phenolic and POSS, and hydroxyl-carbonyl interassociation between phenolic and PMMA. Among these blends, single and higher T(g)s of these phenolic/PMMA-POSS blends were observed than the corresponding phenolic/PMMA blends at same composition, revealing that a stronger interassociation interaction of hydroxyl-siloxane than the hydroxyl-carbonyl interaction. Furthermore, we also found the screening effect in phenolic/LPMMA-POSS blends that tends to significantly decrease the hydrogen bond formation of the hydroxyl-carbonyl interassociation.
Kinetics for the growth of rigid amorphous fraction in cyclic olefin copolymers (COC)
(2001-03-01)
Chu, PPJ
;
Huang, WJ
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
Both linear William-Watts (WW) and non-linear Narayanaswamy-William-Watts (NWW) stretch relaxation satisfactorily described the time dependent rigid amorphous phase growth kinetic. The model is tested upon the completely amorphous cyclic olefin copolymers (COC, polynorbornene/polyethylene copolymer), where a large T-g variation is detected with annealing. Increase of the rigid amorphous fraction as reflected in the increase of T-g, is attributed to the growth of short range ordered phase due to the rigidity of the norbornene chain segment. The analysis shows the growth kinetic (represented by the retardation time, and the stretch exponent) that depends not only on the norbornene (NB) content but also on the NE microblock structure. The kinetics for the growth of the rigid amorphous domains follows a stretched exponential expression, similar to that given for polymer crystallization and physical aging. (C) 2000 Elsevier Science Ltd. All rights reserved.
Matrix formulation of Hamiltonian structures of constrained KP hierarchy
(1998-07-01)
Huang, WJ
;
Shaw, JC
;
Tu, MH
;
應用數學系
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Department of Applied Mathematics
We give a matrix formulation of the Hamiltonian structures of constrained KP hierarchy. First, we derive from the matrix formulation the Hamiltonian structure of the one-constraint KP hierarchy, which was originally obtained by Oevel and Strampp. We then generalize the derivation to the multiconstraint case and show that the resulting bracket is actually the second Gelfand-Dickey bracket associated with the corresponding Lax operator. The matrix formulation of the Hamiltonian structure of the one-constraint KP hierarchy in the form introduced in the study of matrix model is also discussed. (C) 1998 American Institute of Physics. [S0022-2488(98)01207-9].
Miscibility, specific interactions, and self-assembly behavior of phenolic/polyhedral oligomeric silsesquioxane hybrids
(2004-03-15)
Lee, YJ
;
Kuo, SW
;
Huang, WJ
;
Lee, HY
;
Chang, FC
The miscibility of a phenolic resin with polyhedral oligomeric silsesquioxane (POSS) hybrids and the specific interactions between them were investigated with Fourier transform infrared (FTIR) spectroscopy and wide-angle X-ray diffraction (WAXD). An analysis of the morphology and microstructure was performed with polarized optical microscopy and atomic force microscopy (AFM). The interassociation equilibrium constant between the phenolic resin and POSS (38.7) was lower than the self-association equilibrium constant of pure phenolic (52.3) according to the Painter-Coleman association model. This result indicated that POSS was partially miscible with the phenolic resin. A polarized optical microscopy image of a phenolic/POSS hybrid material (20 wt % POSS) indicated that the crystals of POSS were arranged evenly in the phenolic matrix; the self-assembled array of POSS crystals was also confirmed by AFM. This phenomenon was consistent with the FTIR spectroscopy and WAXD analyses. (C) 2004 Wiley Periodicals, Inc.
Miscibility, specific interactions, and spherulite growth rates of binary poly(acetoxystyrene)/poly(ethylene oxide) blends
(2004-06-01)
Kuo, SW
;
Huang, WJ
;
Huang, CF
;
Chan, SC
;
Chang, FC
The binary poly(acetoxystyrene)/poly(ethylene oxide) (PAS/PEO) blend system is fully miscible, as evidenced by a single glass transition temperature over a full range of compositions when analyzed by differential scanning calorimetry analysis, as a result of weak C-(HO)-O-... hydrogen-bonding interactions between the carbonyl groups of PAS and the methylene groups of PEO. One- and two-dimensional correlation spectroscopies provide positive evidence for this specific interaction between the two polymers. In addition, a negative polymer-polymer interaction parameter "chi(12)" was calculated using the Flory-Huggins equation based on the melting depression of PEO. The presence of an amorphous PAS phase results in a reduction in the spherulite growth rate of PEO. Both the values of nucleation constant and the surface free energy of chain folding of PEO decrease with increasing PAS content, which indicates that the crystallization ability of PEO increases correspondingly.
Physical aging of cyclo olefin copolymer (COC)
(2003)
Huang, WJ
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
The physical aging behaviour of the cyclo olefin copolymer (COC) has been investigated in this paper by using low temperature annealing in differential scanning calorimeter (DSC) measurements. The data of recovered enthalpies was fitted by means of Petrie-Marshall (PM), Cowie-Ferguson (CF) or Kohlrausch-Williams-Watts (KWW) form equation in describing the enthalpy relaxation. We have found that the COC sample has a stretched exponential factor near 1.0 (beta = 0.98 +/- 0.02) at the annealing temperature range. The apparent activation energy (EH) of COC aging obtained by using the Petrie/Marshall (PM) analysis method is about 1521.7 +/- 150 kJ/mole. That is substantially higher than 308 50 kJ/mole for bisphenol-A polycarbonate, 407.4 kJ/mole for poly (vinyl methyl ether) and 1192 kJ/mole for polystyrene, but close to 1520 kJ/mole for polyterafluoroethylene (PTFE).
Solid-state NMR study of cyclo-olefin copolymer (COC)
(2000-10-01)
Huang, WJ
;
Chang, FC
;
Chu, PPJ
;
應用化學系
;
Department of Applied Chemistry
In this article, we have applied solid-state C-13 NMR techniques, cross-polarization/magic-angle spinning (CP/MAS), and single-pulse C-13 NMR to characterize the NE conformation of the cyclo-olefin copolymer. The copolymers containing higher NE contents produce more NE blocks according to C-13 CP/MAS spectral analysis. In addition, NB-dyad-based conformations are able to induce peak splitting in the region of 49-52 ppm. (C) 2000 John Wiley & Sons, Inc.
Syntheses and characterizations of in situ blended metallocence polyethylene/clay nanocomposites
(2003-12-01)
Kuo, SW
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Huang, WJ
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Huang, SB
;
Kao, HC
;
Chang, FC
In this paper, we report the preparation of in situ blends of metallocence polyethylene (mPE) with montmorillonite (clay). The polymerization activity of polyethylene decreases upon increasing the amount of the clay feed. The mPE nanocomposites still possess their original melting and crystallization temperatures, but the melting and crystallization enthalpies decrease upon increasing the clay content. In addition, the polymer interaction parameter between mPE and exfoliated clay sheets was calculated to be -0.204 based on a modified Kim-Bae equilibrium melting depression equation. All of the isothermal crystallization kinetics data fit well to the Avrami crystallization equation. We found that increasing the clay content results in a faster rate of crystallization, but pure mPE still crystallizes the fastest. Using a small amount of pretreated clay results in a more homogeneous and finer dispersion of the clay in the polymer matrix, as determined by wide-angle X-ray diffraction and transmission electron microscopy analyses. Both the values of T-1rho(H) in the solid-state NMR spectra of the fast and slow components show increment upon increasing the clay content, which indicates that either the mobile phase tends to increase its rigidity in the clay-containing system. (C) 2003 Elsevier Ltd. All rights reserved.
Synthesis, thermal properties, and specific interactions of high T-g increase in poly(2,6-dimethyl-1,4-phenylene oxide)-block-polystyrene copolymers
(2005-10-24)
Kuo, SW
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Huang, CF
;
Tung, PH
;
Huang, WJ
;
Huang, JM
We have synthesized a series of block copolymers of poly(2,6-dimethyl- 1,4-phenylene oxide) and polystyrene (PPO-b-PS copolymer) by atom transfer radical polymerization. The PS content in these copolymer systems was determined by using infrared spectroscopy, thermal gravimetric analysis, and solution and solid-state NMR spectroscopy; good correlations exist between these characterization methods. DSC analyses indicated that the PPO-b-PS copolymers have higher glass transition temperatures than do their corresponding PPO/PS blends. Our FTIR and solid-state NMR spectroscopic analyses suggest that the PPO-b-PS copolymers possess stronger specific interactions that are responsible for the observed relatively higher values of T-g. We found one single dynamic relaxation from the dynamic mechanical analysis, which implies dynamic homogeneity exists in the PPO-b-PS copolymer; this result is consistent with the one single proton spin-lattice relaxation time observed in the rotating frame [T-1 rho(H)] during solid state NMR spectroscopic analysis. In addition, the 2D FTIR spectroscopy reveals evidence for the stronger interactions between segments of PPO and PS through the formation of pi-cation complexes. (c) 2005 Elsevier Ltd. All rights reserved.
The adaptive lane-departure warning system
(2002)
Hsu, PL
;
Cheng, HY
;
Tsuei, BY
;
Huang, WJ
;
交大名義發表
A vision-based lane-departure warning system which adapts the variation of brightness is developed in this paper. By sequentially applying the proposed processing techniques as (1) lane strengthening, (2) dichotomy, (3) smoothing filtering, an efficient decision rule is then applied to the processed image to realize the lane-departure warning system. Moreover, according to the variation of the brightness by reading the output of a photo-resistance sensor, the adaptive threshold for dichotomy is achieved. The present system effectively achieves real-time lane-departure warning with 10 decisions per second and 97.4% correct detection rate as driving angles varied larger than 50 in the experiments.