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Color-Evaporation-Model Prediction for(e+e−!J/ψ +X) at B Factories
Daekyoung Kang,Jungil Lee,Jong-Wan Lee 한국물리학회 2005 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.47 No.3
The cross section for inclusive J/ roduction in e+e- annihilation at B factories is alculated using the color-evaporation model (CEM). The prediction can be used to estimate the fraction of inclusive J/ + c processes in the inclusive J/ production rate, which is measured by the Belle Collaboration. The color-evaporation-model prediction for the inclusive J/ production crosssection is shown to be about a factor of about 7-8 smaller than the values measured at the Bfactories. The underestimate of the CEM prediction for the inclusive J/ cross-section is observed to become more severe as the available phase space decreases.
Yoo, Daekyoung,Kim, Youngrok,Min, Misook,Ahn, Geun Ho,Lien, Der-Hsien,Jang, Jingon,Jeong, Hyunhak,Song, Younggul,Chung, Seungjun,Javey, Ali,Lee, Takhee American Chemical Society 2018 ACS NANO Vol.12 No.11
<P>One of the long-standing problems in the field of organic electronics is their instability in an open environment, especially their poor water resistance. For the reliable operation of organic devices, introducing an effective protection layer using organo-compatible materials and processes is highly desirable. Here, we report a facile method for the depositing of an organo-compatible superhydrophobic protection layer on organic semiconductors under ambient conditions. The protection layer exhibiting excellent water-repellent and self-cleaning properties was deposited onto organic semiconductors directly using a dip-coating process in a highly fluorinated solution with fluoroalkylsilane-coated titanium dioxide (TiO<SUB>2</SUB>) nanoparticles. The proposed protection layer did not damage the underlying organic semiconductors and had good resistance against mechanical-, thermal-, light-stress-, and water-based threats. The protected organic field-effect transistors exhibited more-reliable electrical properties, even when exposed to strong solvents, due to its superhydrophobicity. This study provides a practical solution with which to enhance the reliability of environmentally sensitive organic semiconductor devices in the natural environment.</P> [FIG OMISSION]</BR>
INCLUSIVE PRODUCTION OF FOUR CHARM HADRONS AT B-FACTORIES
Kang, Daekyoung,Lee, Jungil World Scientific 2006 International journal of modern physics. A, Partic Vol.21 No.4
<P> Measurements by the Belle Collaboration of the exclusive J/ψ + ηc and inclusive [Formula: see text] productions in e<SUP>+</SUP>e<SUP>-</SUP> annihilation differ substantially from theoretical predictions based on the nonrelativistic QCD factorization approach. In order to test if such a discrepancy is originated from the large perturbative corrections to the hard-scattering amplitude, we study inclusive production of four charm hadrons in e<SUP>+</SUP>e<SUP>-</SUP> annihilation at B factories. </P>
Kim, Daekyoung,Kim, Hoonbae,Jang, Haegyu,Jung, Donggeun,Chae, Heeyeop American Scientific Publishers 2012 Journal of nanoscience and nanotechnology Vol.12 No.7
<P>Ultra low-k dielectric SiCOH films were deposited with decamethylcyclopentasiloxane (DMCPSO, C10H30O5Si5) and cyclohexane (C6H12) precursors by plasma-enhanced chemical vapor deposition at the deposition temperature between 25 and 200 degrees C and their chemical composition and deposition kinetics were investigated in this work. Low dielectric constants of 1.9-2.4 were obtained due to intrinsic nanoscale pores originating from the relatively large ring structure of DMCPSO and to the relatively large fraction of carbon contents in cyclohexane. Three different deposition regions were identified in the temperature range. Deposition rates increased with temperature below 40 degrees C and decreased as temperature increased to 75 degrees C with apparent activation energies of 56 kJ/mol x K at < 40 degrees C, -26 kJ/mol x K at 40-100 degrees C, respectively. In the temperature region of 40-100 degrees C hydrocarbon deposition and decomposition process compete each other and decomposition becomes dominant, which results in apparent negative activation energy. Deposition rates remain relatively unaffected with further increases of temperature above 100 degrees C. FTIR analysis and deposition kinetic analysis showed that hydrocarbon deposition is the major factor determining chemical composition and deposition rate. The hydrocarbon deposition dominates especially at lower temperatures below 40 degrees C and Si-O fraction increases above 40 degrees C. We believe that dielectric constants of low-k films can be controlled by manipulating the fraction of deposited hydrocarbon through temperature control.</P>
Kim, Daekyoung,Fu, Yan,Kim, Jungwoo,Lee, Ki-heon,Kim, Hyoungsub,Yang, Heesun,Chae, Heeyeop IOP 2016 Nanotechnology Vol.27 No.24
<P>In this study, benzenethiol ligands were applied to the surface of CdSe@ZnS core@shell quantum dots (QDs) and their effect on the performance of quantum dot light-emitting diodes (QD-LEDs) was investigated. Conventional long-chained oleic acid (OA) and trioctylphosphine (TOP) capping ligands were partially replaced by short-chained benzenethiol ligands in order to increase the stability of QDs during purification and also improve the electroluminescence performance of QD-LEDs. The quantum yield of the QD solution was increased from 41% to 84% by the benzenethiol ligand exchange. The mobility of the QD films with benzenethiol ligands approximately doubled to 2.42 × 10<SUP>−5</SUP> cm<SUP>2</SUP> V<SUP>−1</SUP> s<SUP>−1</SUP> from 1.19 × 10<SUP>−5</SUP> cm<SUP>2</SUP> V<SUP>−1</SUP> s<SUP>−1</SUP> compared to the device consisting of OA/TOP-capped QDs, and an approximately 1.8-fold improvement was achieved over QD-LEDs fabricated with bezenethiol ligand-exchanged QDs with respect to the maximum luminance and current efficiency. The turn-on voltage decreased by about −0.6 V through shifting the energy level of the QDs with benzenethiol ligands compared to conventional OA and TOP ligands.</P>
Kim, Daekyoung,Fu, Yan,Kim, Sunho,Lee, Woosuk,Lee, Ki-Heon,Chung, Ho Kyoon,Lee, Hoo-Jeong,Yang, Heesun,Chae, Heeyeop American Chemical Society 2017 ACS NANO Vol.11 No.2
<P>We report on an all-solution-processed fabrication of highly efficient green quantum dot -light emitting diodes (QLEDs) with an inverted architecture, where an interfacial polymeric surface modifier of polyethylenimine ethoxylated (PETE) is inserted between a quantum dot (QD) emitting layer (EML) and a hole transport layer (HTL), and a MoOx hole injection layer is solution deposited on top of the HTL. Among the inverted QLEDs with varied PEIE thicknesses, the device with an optimal PEIE thickness of 15.5 nm shows record maximum efficiency values of 65.3 cd/A in current efficiency and 15.6% in external quantum efficiency (EQE). All-solution processed fabrication of inverted QLED is further implemented on a flexible platform by developing a high-performing transparent conducting composite film of ZnO nanoparticles-overcoated on Ag nanowires. The resulting flexible inverted device possesses 35.1 cd/A in current efficiency and 8.4% in EQE, which are also the highest efficiency values ever reported in flexible QLEDs.</P>