The National Synchrotron Radiation Research Center is a 1.5 GeV third-generation synchrotron at the Hsinchu Science Park in East District, Hsinchu City, Taiwan as the agency under the Ministry of Science and Technology of the Republic of China.There are twenty-six operational beamlines and four under construction; the NSRRC also operate two beamlines at SPring-8 in Japan. They cover a wide range of functionality, from IR microscopy to X-ray lithography. Wikipedia.
Chen W.-T.,National Taiwan University |
Sheu H.-S.,National Synchrotron Radiation Research Center |
Liu R.-S.,National Taiwan University |
Attfield J.P.,University of Edinburgh
Journal of the American Chemical Society | Year: 2012
Red or yellow phosphors excited by a blue light-emitting diode are an efficient source of white light for everyday applications. Many solid oxides and nitrides, particularly silicon nitride-based materials such as M 2Si 5N 8 and MSi 2O 2N 2 (M = Ca, Sr, Ba), CaAlSiN 3, and SiAlON, are useful phosphor hosts with good thermal stabilities. Both oxide/nitride and various cation substitutions are commonly used to shift the emission spectrum and optimize luminescent properties, but the underlying mechanisms are not always clear. Here we show that size-mismatch between host and dopant cations tunes photoluminescence shifts systematically in M 1.95Eu 0.05Si 5-xAl xN 8-xO x lattices, leading to a red shift when the M = Ba and Sr host cations are larger than the Eu 2+ dopant, but a blue shift when the M = Ca host is smaller. Size-mismatch tuning of thermal quenching is also observed. A local anion clustering mechanism in which Eu 2+ gains excess nitride coordination in the M = Ba and Sr structures, but excess oxide in the Ca analogues, is proposed for these mismatch effects. This mechanism is predicted to be general to oxynitride materials and will be useful in tuning optical and other properties that are sensitive to local coordination environments. © 2012 American Chemical Society. Source
Hy S.,National Taiwan University of Science and Technology |
Felix F.,National Taiwan University of Science and Technology |
Rick J.,National Taiwan University of Science and Technology |
Su W.-N.,National Taiwan University of Science and Technology |
And 2 more authors.
Journal of the American Chemical Society | Year: 2014
High-capacity layered, lithium-rich oxide cathodes show great promise for use as positive electrode materials for rechargeable lithium ion batteries. Understanding the effects of oxygen activating reactions on the cathode's surface during electrochemical cycling can lead to improvements in stability and performance. We used in situ surfaced-enhanced Raman spectroscopy (SERS) to observe the oxygen-related surface reactions that occur during electrochemical cycling on lithium-rich cathodes. Here, we demonstrate the direct observation of Li2O formation during the extended plateau and discuss the consequences of its formation on the cathode and anode. The formation of Li 2O on the cathode leads to the formation of species related to the generation of H2O together with LiOH and to changes within the electrolyte, which eventually result in diminished performance. Protection from, or mitigation of, such devastating surface reactions on both electrodes will be necessary to help realize the potential of high-capacity cathode materials (270 mAhg-1 versus 140 mAhg-1 for LiCoO2) for practical applications. © 2013 American Chemical Society. Source
Lee S.-H.,National Synchrotron Radiation Research Center
Physical Chemistry Chemical Physics | Year: 2010
We investigated the photodissociation dynamics of tetrahydrofuran (c-C 4H8O) at 193.3 nm in a molecular-beam apparatus using photofragment-translational spectroscopy and direct vacuum-ultraviolet (VUV) photoionization. Five dissociation channels leading to products with m/z ratios appropriate for CH2CH2CH2 + H2CO, CH2CHCH2 + CH2OH, H + CH2CH 2 + CH2CHO, CH2CH2 + CH3 + HCO and CH2CH2 + CH2CO + H2 were identified; their branching ratios were determined to be 0.40, 0.25, 0.04 0.29 and 0.02, respectively. Secondary dissociations from nascent products CH 2CH2CH2CHO to CH2CH2 + CH2CHO and from CH2CH2O to CH3 + HCO and likely to CH2CO + H2 were observed. We measured distributions of product kinetic energy, average kinetic-energy release, and fractions in translation for each dissociation channel. The formation of CH 2CHCH2 + CH2OH indicates that hydrogen migration occurs before complete fragmentation. All photofragments have nearly isotropic angular distributions, with β values less than 0.05. The photodissociation of tetrahydrofuran into five channels is proposed to proceed mainly on the ground state potential-energy surface following ring opening and efficient internal conversions. © the Owner Societies. Source
Yuh J.-Y.,National Synchrotron Radiation Research Center
Journal of Synchrotron Radiation | Year: 2014
A simple design and easily installed tool for alignment has been developed for time-sharing undulator beamlines. A laser beam is directed onto a beam splitter inside the vacuum chamber, then reflects 90° along the synchrotron beam path; this beam serves as a reference to mimic the synchrotron beam path. Use of this tool greatly abbreviated alignment of an end-station after beamline switching; both beamline diagnosis and end-station development can be completed before the synchrotron beam time begins. © 2014 International Union of Crystallography. Source
National Synchrotron Radiation Research Center | Date: 2013-11-15
An X-ray mask structure includes a unibody support substrate having at least one thinned portion surrounded by a wall portion, a top layer disposed on the at least one thinned portion of the support substrate, and a plurality of X-ray absorber patterns disposed on the top layer over the at least one thinned portion. The top layer and the at least one thinned portion form a laminated membrane, wherein the at least one thinned portion and the wall portion provide mechanical support for the top layer, and the laminated membrane provides mechanical support for the plurality of X-ray absorber patterns.