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21.
Low-temperature growth of GaN by atomic nitrogen based on a dielectric barrier discharge 总被引:1,自引:0,他引:1
GaN films were deposited on sapphire(0 0 0 1) and Si(1 0 0) substrates by MOCVD using an atomic nitrogen source based on a dielectric barrier discharge (DBD) method. Molecule nitrogen and trimethylgallium (TMG) were separately delivered to the substrates. Wurtzite GaN films, with no trace of cubic GaN, were successfully grown on -Al2O3 substrates even at relatively low temperatures (<800°C). Sapphire substrate RMS roughness was 5.01 and 4.93 Å before and after the exposure to DBD N-source, respectively. This shows negligible irradiation damage of accelerated N2+ ion as well as the effect of smoothening the substrate surfaces with DBD N-source. The PL results exhibited small luminescence at the spectral region of blue and UV but a luminescence around the yellow region (2.5 eV) was detected. This is caused by oxygen impurity from AES analysis. 相似文献
22.
We show that penalized functions of the Fischer–Burmeister and the natural residual functions defined on symmetric cones are
complementarity functions. Boundedness of the solution set of a symmetric cone complementarity problem, based on the penalized
natural residual function, is proved under monotonicity and strict feasibility. The proof relies on a trace inequality on
Euclidean Jordan algebras. 相似文献
23.
Yong?Nam?Kim Jong?Min?Kum Hyeok?Moo?Lee Sung?Oh?ChoEmail author 《Journal of nanoparticle research》2012,14(4):774
A novel approach to pattern nanocrystalline gold (Au) octahedra is presented based on electron irradiation combined with thermal
treatment and post-cleaning process using HAuCl4-loaded poly(styrene-b-2-vinyl pyridine) (PS-b-P2VP) block copolymer (BCP) as a precursor material. The BCP tends to cross-link
under electron irradiation, and thus a patterned film can be prepared by selectively irradiating an electron beam onto a precursor
film using a shadow mask. A post-thermal treatment leads to the formation of crystalline Au nano-octahedra inside the patterned
film with a help of the BCP acting as a capping agent. Subsequently, the BCP can be removed by O2 plasma etching combined with oxidative degradation, with the Au nanoparticles remaining. As a result, a patterned film consisting
of high-purity nanocrystalline Au octahedra is fabricated. The sizes of the Au octahedral nanoparticles can be readily controlled
from 49 to 101 nm by changing the thickness of the precursor film. The patterned Au nano-octahedra films exhibit excellent
surface-enhanced Raman scattering behavior with the maximum enhancement factor of ~106. 相似文献
24.
Lee KH Kwon YS Lee JY Kang S Yook KS Jeon SO Lee JY Yoon SS 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(46):12994-13006
Blue fluorescent materials with a 2‐(diphenylamino)fluoren‐7‐ylvinylarene emitting unit and tert‐butyl‐based blocking units were synthesized. The photophysical properties of these materials, including UV/Vis absorption, photoluminescent properties, and HOMO–LUMO energy levels, were characterized and rationalized with quantum‐mechanical DFT calculations. The electroluminescent properties of these molecules were examined through the fabrication of multilayer devices with a structure of indium–tin oxide, 4,4′‐bis{N‐[4‐(N,N‐di‐m‐tolylamino)phenyl]‐N‐phenylamino}biphenyl, 4′‐bis[N‐(1‐naphthyl)‐N‐phenylamino]biphenyl, and blue materials doped in 2‐methyl‐9,10‐di(2‐naphthyl)anthracene/tris(8‐quinolinolato)aluminum/LiF/Al. All devices exhibit highly efficient blue electroluminescence with high external quantum efficiency (3.20–7.72 % at 20 mA cm?2). A deep‐blue device with Commission Internationale de l’Eclairage (CIE) coordinates of (0.15, 0.11) that uses 7‐[2‐(3′,5′‐di‐tert‐butylbiphenyl‐4‐yl)vinyl]‐9,9‐diethyl‐2‐N‐(3,5‐di‐tert‐butylphenyl)‐2,4‐difluorobenzenamino‐9H‐fluorene as a dopant in the emitting layer showed a luminous efficiency and external quantum efficiency of 3.95 cd A?1 and 4.23 % at 20 mA cm?2, respectively. Furthermore, a highly efficient sky‐blue device that uses the dopant 7‐{2‐[2‐(3,5‐di‐tert‐butylphenyl)‐9,9′‐spirobifluorene‐7‐yl]vinyl}‐9,9‐diethyl‐2‐N,N‐diphenylamino‐9H‐fluorene exhibited a luminous efficiency and high quantum efficiency of 10.3 cd A?1 and 7.7 % at 20 mA cm?2, respectively, with CIE coordinates of (0.15, 0.20). 相似文献
25.
Seok Kyun Noh Mijung Lee Don Ho Kum Kiseok Kim Won Seok Lyoo Dong‐Ho Lee 《Journal of polymer science. Part A, Polymer chemistry》2004,42(7):1712-1723
The new dinuclear half‐sandwich CGC (constrained geometry catalyst) with methyl substitution in indenyl, [Ti(η5:η1‐2‐methylindenyl)SiMe2NCMe3]2 [(CH2)n] [n = 6 ( 10 ), n = 9 ( 11 ), n = 12 ( 12 )], have been synthesized, and structure of these complexes has been characterized by 1H and 13C NMR. The most important feature is that two protons of methylene directly bonded to the indenyl ring become inequivalent to be shown as two separated resonances at 2.9 and 3.0 ppm, probably due to the formation of planar chirality caused by a titanium complex formation. It has been found that the dinuclear CGCs with methyl substitution at an indenyl ring were very active catalysts for ethylene and styrene copolymerization. The activity increases in the order of 10 < 11 < 12 , which indicates that the presence of a longer bridge between two active sites contributes to facilitate the polymerization activity of the dinuclear CGC more effectively. This result might be understood by the implication that the steric factor rather than the electronic factor may play a major role to direct the polymerization behavior of the dinuclear CGC. It is found that the dinuclear catalysts are very efficient to incorporate styrene in the polyethylene backbone. The styrene contents in the formed copolymers ranged from 5 to 40% according to the polymerization conditions. One can observe strong signals at 29.7 ppm of the polyethylene sequences, and, in addition, peaks at 27.5, 36.9, and 46. 2ppm (Sβδ, Sαδ, and Tδδ, respectively) of sequences of EESEE. Weak peak at 25.3 ppm are attributed to Sββ, which represents SES sequence. The absence of a signal for Tββ at 41.3 ppm and for Sαα at 43.6 ppm shows there is no styrene–styrene sequences in copolymers. This result indicates that the dinuclear CGC are very effective to generate well‐distributed poly(ethylene‐co‐styrene)s. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1712–1723, 2004 相似文献
26.
Red Phosphorescent Bis‐Cyclometalated Iridium Complexes with Fluorine‐, Phenyl‐, and Fluorophenyl‐Substituted 2‐Arylquinoline Ligands 下载免费PDF全文
Jwajin Kim Dr. Kum Hee Lee Dr. Seok Jae Lee Dr. Ho Won Lee Prof. Young Kwan Kim Prof. Young Sik Kim Prof. Seung Soo Yoon 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(12):4036-4045
Red phosphorescent iridium(III) complexes based on fluorine‐, phenyl‐, and fluorophenyl‐substituted 2‐arylquinoline ligands were designed and synthesized. To investigate their electrophosphorescent properties, devices were fabricated with the following structure: indium tin oxide (ITO)/4,4′,4′′‐tris[2‐naphthyl(phenyl)amino]triphenylamine (2‐TNATA)/4,4′‐bis[N‐(1‐naphthyl)‐N‐phenylamino]biphenyl (NPB)/4,4′‐bis(N‐carbazolyl)‐1,1′‐biphenyl (CBP): 8 % iridium (III) complexes/bathocuproine (BCP)/tris(8‐hydroxyquinolinato)aluminum (Alq3)/8‐hydroxyquinoline lithium (Liq)/Al. All devices, which use these materials showed efficient red emissions. In particular, a device exhibited a saturated red emission with a maximum luminance, external quantum efficiency, and luminous efficiency of 14200 cd m?2, 8.44 %, and 6.58 cd A?1 at 20 mA cm?2, respectively. The CIE (x, y) coordinates of this device are (0.67, 0.33) at 12.0 V. 相似文献
27.
For the nonlinear complementarity problem (NCP), Chen et al. (Math. Program., 88:211–216, 2000) proposed a penalized Fischer-Burmeister (FB) function that has most desirable properties among complementarity functions (C-functions). Motivated by their work, the authors showed
(Kum and Lim in Penalized Complementarity Functions on Symmetric Cones, submitted, 2009) that this function naturally extends to a C-function for the symmetric cone complementarity problem (SCCP). In this note, we show that the main coercivity property of this function for NCP also extends to the SCCP. The proof
uses a new trace inequality on Euclidean Jordan algebras. We also show that the penalized FB function is strongly semismooth
in the case of a semidefinite cone and a second-order cone.
This work was supported by the Korea Research Foundation Grant KRF-2008-314-C00039. 相似文献
28.
The reaction between nitrogenous organic bases and ammonium reineckate was studied and was found to depend on the basicity of the bases and the pH of the reaction media. An expression is given which relates the dissociation constant pKb of a base and the pH of the reaction ; when the pKb of a base is known the pH required for the complex formation can be calculated. The conditions for the formation of reineckates of very weak bases together with the formation of mono and di-reineckates of dibasic substances are given. The separation of bases whose pKb values are sufficiently far apart and the determination of mixtures of mono- and dibasic substances were effected by pH adjustment of the reaction media. The isolation of strychnine from putrified human livers is also described. 相似文献
29.
This paper considers the existence of solutions and the equivalence of four kinds of vector variational inequalities (VVI). More precisely, a sufficient condition is provided under which the solution sets of these VVIs are nonempty and equal. An example is given, showing that such a sufficient condition is essential to ensure the results. Actually, the main theorems in this paper can be regarded as a suitable correction and a refinement of recent results due to Chang et al. (Ref. 1). 相似文献
30.
Ummihan Taskopran Yilmaz Goknur Ozdemir Kum Saliha Alan Akman Hasim Yilmaz 《Russian Journal of Electrochemistry》2018,54(1):20-26
A differential pulse polarographic (DPP) method has been used for the indirect determination of Hg(II). With a known amount of cyanuric acid (CA) in polarography cell (B–R buffer, pH 10.5) was added an unknown Hg(II) sample and the Hg(II) concentration is calculated simply from the decrease in the CA peak after reaction with Hg(II). The linear concentration range was between 20 and 120 μM and limit of detection was calculated to be 6.7 μM. The proposed method was successfully applied to the dried leave samples belong to C. comosum plant. The method was extended to the indirect determination of mercury(II) in C. comosum plant and results were in agreement with that obtained by a spectrometric comparison method (ICP-MS). The sufficiently good recoveries and low standard deviations reflect the high accuracy of developed method. 相似文献