Browsing by Author "Liu, KP"

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High resolution x-ray micromachining using SU-8 resist
(2003-09-01)
Shew, BY
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Hung, JT
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Huang, TY
;
Liu, KP
;
Chou, CP
This paper investigates the feasibility of using SU-8 as a high contrast x-ray resist. The SU-8 resist was irradiated with various x-ray doses and then developed for a fixed time. The developing rate was then measured and plotted versus absorbed x-ray dosage. The results revealed that SU-8 exhibited very high lithographic contrast other than elevated sensitivity. Therefore, a very thin mask absorber is required to switch the negative resist 'ON' or 'OFF'. Preliminary results showed that 1 mum wide, 17 mum thick SU-8 resists could be successfully patterned using an absorber of submicron thickness. Once the absorber thickness is effectively reduced to less than 1 mum, a high-resolution x-ray mask can be patterned simply by conventional UV lithography. An extra soft x-ray beamline was not required to increase the absorber's thickness in certain cases. The process of fabricating the membrane x-ray mask could thus be considerably simplified. X-ray micromachining may be an easy way to pattern high-resolution and high-aspect-ratio microstructures for optical and photonic applications.
Imaging the pair-correlated excitation function: The F+CH4 -> HF(v ')+CH3 (nu=0) reaction
(2004-01-01)
Shiu, W
;
Lin, JJ
;
Liu, KP
;
Wu, M
;
Parker, DH
The velocity map ion imaging technique was applied to measure the reaction excitation function for the first time. It was found that the "raw" excitation function was significantly distorted by the density-to-flux transformation of the title reaction. Through a systematic investigation, possible reasons for such a dramatic effect are outlined. In addition, the state-resolved, pair-correlated excitation functions and branching ratios are presented. Effects of imperfect time slicing in the time-sliced velocity imaging technique in general are also discussed. (C) 2004 American Institute of Physics.
Insights into dynamics of the F+CD4 reaction via product pair correlation
(2003-09-08)
Zhou, JG
;
Lin, JJ
;
Shiu, WC
;
Liu, KP
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應用化學系
To unravel the "extra-atom" complexity of the title reaction, we exploit an experimental approach which, by taking advantage of the correlated information of coincident product pairs, allows us to peel off judiciously the intrinsic complications of a six-atom reaction, extracting the underlying backbone of three-atom dynamics. Examining the collisional energy dependencies of the pair-correlated attributes for a given state(s) of CD3 products from the title reaction, several of major observations can qualitatively be understood, whereas others await further theoretical investigations. An intriguing possibility for the existence of reactive resonances in this six-atom reaction is surmised. (C) 2003 American Institute of Physics.
Observation of a reactive resonance in the integral cross section of a six-atom reaction: F+CHD3
(2004-07-08)
Zhou, JG
;
Lin, JJ
;
Liu, KP
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應用化學系
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Department of Applied Chemistry
The title reaction was investigated under crossed-beam conditions at collisional energies ranging from about 0.4 to 7.5 kcal/mol. Product velocity distributions were measured by a time-sliced, velocity-map imaging technique to explicitly account for the density-to-flux transformation factors. Both the state-resolved, pair-correlated excitation functions and vibrational branching ratios are presented for the two isotopic product channels. An intriguing resonance tunneling mechanism occurring near the reaction threshold for the HF+CD3 product channel is surmized, which echoes the reactive resonances found previously for the F+HD-->HF+D reaction and more recently for the F+CH4 reaction. (C) 2004 American Institute of Physics.
On the Cl*(P-2(1/2)) reactivity and the effect of bend excitation in the Cl+CH4/CD4 reactions
(2004-09-30)
Zhou, JG
;
Lin, JJ
;
Zhang, BL
;
Liu, KP
;
應用化學系
The reaction of atomic chlorine with methane was studied in crossed-beam experiments at a collisional energy of E-c approximate to 4.7 kcal/mol. Using a time-sliced product imaging technique, several outstanding issues about this reaction were addressed in this work. It was found that the reactivity of the spin-orbit excited Cl*(P-2(1/2)) atom toward methane is negligibly small, in agreement with the assertion of recent studies. The excitation of methane bending/torsional modes exhibits only modest enhancement in reactivity, in contrast to the previous experiments. The product angular distributions are mainly backscattered for Cl + CD4, and sideways scattered for Cl + CH4. The shapes of the distributions from the ground state and the bend-excited methane are remarkably similar.
Oxygen quenching effect in ultra-deep X-ray lithography with SU-8 resist
(2004-03-01)
Shew, BY
;
Huang, TY
;
Liu, KP
;
Chou, CP
;
機械工程學系
An ultra-thick (1.5 mm) SU-8 resist was prepared and patterned using synchrotron x-rays. The lithographic sensitivity of the SU-8 resist is over 100 times higher than that of the traditional PMMA resist. However, preliminary results showed that the standard resist process produced poor lithographic quality. The fluorescence induced by high-energy x-ray irradiation was believed to blur the transfer pattern. The lithographic quality improved significantly if the resists were relaxed in an oxygen atmosphere before being soft baked. The FTIR spectrum displayed new absorption peaks, corresponding to the C=O bond, in the oxygen-relaxed resists. The development rates of the low-dosed resists increased if they were held in the oxygen atmosphere, implying that trapped oxygen restrains the cross linking of the SU-8 resist. Based on these observations, this study proposes an oxygen quenching mechanism for interpreting these phenomena. When the SU-8 is oxygen relaxed, the oxygen molecules will gradually diffuse into the resist. Oxygen is a strong free-radical scavenger, and thus kills the free radicals generated by fluorescence, providing a clear pattern defined by x-ray irradiation. After the SU-8 resist was properly oxygen treated, the maximum dimension error was only about 2 mum for a 1.5 mm-thick SU-8 resist. This lithographic quality is good enough to meet the micromachining requirements for mm-wave RF (radio frequency) cavity applications.
Reactive resonance in a polyatomic reaction
(2004-03-12)
Shiu, W
;
Lin, JJ
;
Liu, KP
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應用化學系
;
Department of Applied Chemistry
In the course of an extensive investigation aimed at understanding the detailed mechanisms of a prototypical polyatomic reaction, several remarkable observations were uncovered. To interpret these findings, we surmise the existence of a reactive resonance in this polyatomic reaction. The reaction of concern is F+CH4-->HF+CH3, and the abnormal attributes were revealed only near the reaction threshold. The discovery of reactive resonance in a polyatomic reaction is more than just an extension from a typical atom+diatom reaction. As shown here, it holds great promise to disentangle the elusive intramolecular vibrational dynamics of transient collision complex in the critical transition-state region.
Rotationally selected product pair correlation in F+CD4 -> DF(nu('))+CD3(nu=0,N)
(2004-04-01)
Zhou, JG
;
Shiu, WC
;
Lin, JJ
;
Liu, KP
;
應用化學系
The title reaction was studied in a crossed-beam experiment by imaging of state-selected products. The rotational state selection of the CD3 products was achieved using (2+1) resonance-enhanced multiphoton ionization. The coincident information on the DF coproducts was revealed in a state-resolved manner from time-sliced velocity map images. Significant dependences of both the correlated differential cross sections and the DF vibrational branching ratios on the "tagged" CD3 rotation states were found. The dynamical implications of one of the major findings are discussed. (C) 2004 American Institute of Physics.