989 resultados para H2O
Resumo:
InGaN/GaN multi-quantum-well blue (461 +/- 4 nm) light emitting diodes with higher electroluminescence intensity are obtained by postgrowth thermal annealing at 720 C in O-2-ambient. Based on our first-principle total-energy calculations, we conclude that besides dissociating the Mg-H complex by forming H2O, annealing in O-2 has another positive effect on the activation of acceptor Mg in GaN. Mg can be further activated by the formation of an impurity band above the valence band maximum of host GaN from the passivated Mg-Ga-O-N complex. Our calculated ionization energy for acceptor Mg in the passivated system is about 30 meV shallower than that in pure GaN, in good agreement with previous experimental measurement. Our model can explain that the enhanced electroluminescence intensity of InGaN/GaN MQWs based on Mg-doped p-type GaN is due to a decrease in the ionization energy of Mg acceptor with the presence of oxygen. (C) 2008 American Institute of Physics.
Resumo:
InGaN/GaN-multiple-quantum-well-based light emitting diode ( LED) nanopillar arrays with a diameter of approximately 200nm and a height of 700nm are fabricated by inductively coupled plasma etching using Ni self-assembled nanodots as etching mask. In comparison to the as-grown LED sample an enhancement by a factor of four of photoluminescence ( PL) intensity is achieved after the fabrication of nanopillars, and a blue shift and a decrease of full width at half maximum of the PL peak are observed. The method of additional wet etching with different chemical solutions is used to remove the etch-induced damage. The result shows that the dilute HCl ( HCl:H2O=1:1) treatment is the most effective. The PL intensity of nanopillar LEDs after such a treatment is about 3.5 times stronger than that before treatment.
Resumo:
Self-assembled InAs/AlAs quantum dots embedded in a resonant tunneling diode device structure are grown by molecular beam epitaxy. Through the selective etching in a C6H8O7 center dot H2O-K3C6H5O7 center dot H2O-H2O2 buffer solution, 310 nm GaAs capping layers are removed and the InAs/AlAs quantum dots are observed by field-emission scanning electron microscopy. It is shown that as-fabricated quantum dots have a diameter of several tens of nanometers and a density of 10(10) cm(-2) order. The images taken by this means are comparable or slightly better than those of transmission electron microscopy. The undercut of the InAs/AlAs layer near the edges of mesas is detected and that verifies the reliability of the quantum dot images. The inhomogeneous oxidation of the upper AlAs barrier in H2O2 is also observed. By comparing the morphologies of the mesa edge adjacent regions and the rest areas of the sample, it is concluded that the physicochemical reaction introduced in this letter is diffusion limited.
Resumo:
HeH2OCO25A5AH2OCO2H2OCO2HeH2OCO21055A
Resumo:
The replacement of CH4 from its hydrate in quartz sand with 90:10, 70:30, and 50:50 (W-CO2:W-H2O) carbon dioxide-in-water (C/W) emulsions and liquid CO2 has been performed in a cell with size of empty set 36 x 200 mm. The above emulsions were formed in a new emulsifier, in which the temperature and pressure were 285.2 K and 30 MPa, respectively, and the emulsions were stable for 7-12 h. The results of replacing showed that 13.1-27.1%, 14.1-25.5%, and 14.6-24.3% of CH4 had been displaced from its hydrate with the above emulsions after 24-96 It of replacement, corresponding to about 1.5 times the CH4 replaced with high-pressure liquid CO2. The results also showed that the replacement rate of CH4 with the above emulsions and liquid CO2 decreased from 0.543, 0.587, 0.608, and 0.348 1/h to 0.083, 0.077, 0.069, and 0.063 1/h with the replacement time increased from 24 to 96 h. It has been indicated by this study that the use of CO2 emulsions is advantageous compared to the use of liquid CO2 in replacing CH4 from its hydrate.
Resumo:
Al-doped and B, Al co-doped SiO2 xerogels with Eu2+ ions were prepared only by sol-gel reaction in air without reducing heat-treatment or post-doping. The luminescence characteristics and mechanism of europium doping SiO2 xerogels were studied as a function of the concentration of Al, B, the europium concentration and the host composition. The emission spectra of the Al-doped and B, Al codoped samples all show an efficient emission broad band in the blue violet range. The blue emission of the Al-doped sample was centered at 437 nm, whereas the B, Al co-doped xerogel emission maximum shifted to 423 nm and the intensity became weaker. Concentration quenching effect occurred in both the Al-doped and B, Al co-doped samples, which probably is the result of the transfer of the excitation energy from Eu2+ ions to defects. The highest Eu2+ emission intensity was observed for samples with the Si(OC2H5)(4):C2H5OH:H2O molar ratio of 1:2:4. (c) 2006 Elsevier B.V. All rights reserved.
Resumo:
5 cm10 cm,()()1 cm3 cm6cm9cm12 cm5,Vandervaere,Philip,,,,;,,;,;,,;,,,5 cm-12 cm10 cm-9 cm-12 cm30~40 s40~50 s;30 s;,10 cm-9 cm-12 cm30~40 s40~50 s,30 s
Resumo:
,,,"134""253"6,,,3,,22.03μmol CO2.m-2.s-1),7.12μmol CO2/mmol H2O,1.632.05,,,
Resumo:
12020 cm,TiessenMoirHedley:P:HCl-P>Residual-P>NaHCO3-Po>NaHCO3-Pi>NaOH-Po>NaOH-Pi>H2O-P,HCl-PResidual-P,54.00%88.96%039.11%,NaOH-PoResidual-P<<<,;H2O-PHCl-P<<<,,,NaOH-PiNaOH-PoHCl-PC/NpH,pHNaHCO3-Po,H2O-PNaHCO3-Pi...
Resumo:
- N-(3-)(110)(C6H13N3)2PbBr4 (monoclinic, P21/c)(392 nm)(424 nm)N-(3-)CASTEP (Cambridge Serial Total Energy Package) 2-(2-)(110)C3H11SN3PbBr4(monoclinic P21/c)2-(2-)(110)N-(3-)(110) -()-()-()0-D [(m-C6H10N2)2PbBr6] (orthorhombic, Pbca), 1-D [(o-C6H10N2)PbBr4] (monoclinic, P21/c), 2-D [p-(C6H10N2)PbBr4] (orthorhombic, Pbca) -()0-D-()2-D-()428 nm(0-D)431 nm(1-D)461 nm (0-D)467 nm(1-D) 3-4-3-Pb-Br(C6H13N3)PbBr4 (monoclinic, C2/c)4-(100)(C6H13N3)PbBr4(orthorhombic, Pbca) (100)(C5H10N3)PbBr4 (monoclinic, P21/c)(C5H10N3)PbCl4 (monoclinic, P21/c)(419 nm339 nm)3--1,2,4-PbBr2(C2H2N4)PbBr3 (orthorhombic, Pna21) 2,2΄-(-)4,4΄-(-)2,2΄-(-)(C7H8N2)PbCl3 (triclinic, P-1)(C7H8N2)PbBr3 (triclinic, P-1)4,4΄-(-)(C20H21N4)Pb2Cl6•H2O (triclinic, P-1)(C20H21N4)Pb2Br6 (monoclinic, C2/c)-*
Resumo:
21DMFCDNDFC""Pt/CPC11Pt/CP"CRCPtPUCPC2CoPcTcCFeTPPC800CoPcTcCXPSXRDCoN4FeTPPCCoPcTcC7003FeTPP-Pt/CFeTPP-Pt/CPCFeTPPPtFeTPP-PtCPt/CFeTPPPt/CR700FeTPP-Pt/CDMFC4FeTPP-TiO2/C70FeTPP-TiO2CTIOZFeTPPH2O2O2H2OFeTPPTIOZ21Pt/CPt/CXRDXPSTEMPtPt/CPt/CPt/C2FeTPP-Pt/CFeTPPPt3Pt/CVulcanXC-72Pt/CPCPEMFC4-11MP-11CMP-11CO2
Resumo:
,-L20ZnbpyCSH6O41CubpyCSH6o4244MllbpyCSH12O4HZO312znbpyC6HSO4444382140oC4180-32044-35-30OKCurie-WeissXm-l4.265T+6.3MZhmtHZO2C3HZO42MMnII5CuII65530OKCurieWeissXm-18.99T+4.5MnHZO4bpyC4H4O44H207MnH2O4bpyc4HZO44H208ZnH2O4bpyC4H4O44H2091MH2O4 bpy2/22+CuH2O4bpyC4H2O44H2O 10NiH2O4bpyC4H2O44HZO 1179MH2O4bpy222Cuimid2H2OLL1213CumidH2O2+Cuimid2C6H8O414cuCuC3C3H42 C6H8O433Cuimid2C6H9O42CuCuC3N2H42(C6H9O4)4/212256000cCuimid2C4H4O4CuO1314TG14155300Kcuriew155m-0.371T-4.6Xm-l:0.4095T-1.2NCumal2ZHZO 16KZCumal23HZO 17RbZCumal2H2O 18C82Cumal2' 4H2O19161716-19Cuimid4ClCl 21CICuimidCI11925500I23CO16195300KCurie-WesissXm-lCT- 4354263 06439KC0.43410.41720.42320.4113cm3K.mol-1
Resumo:
VACRpI~(0.5)[SLS]~(0.12)[V_M/V_(H2O)]~(0.03)N[SLS]~(0.48); RpN~(0.24)N10%N5.7/VAcNFriisVAcKd'Kd'FriisKd'PVAcPVAcFriisVAcK_(tnm)K_(tnp)PVAcK_(tnm)K_(tnp)PVAcPVAPVAcPVAPVAcPVATg, Tm, TdTg, Td, TmTgPVAcPVAPVAcPVA
Resumo:
Al-LiAl-LiNaAl-LiAl-Li Al-LiLiCl-KCl-LiFLiAlNaAl-LiLiCl1NH_4ClLi_2CO_3 200 Li_2CO_3 + 2NN_4Cl = 2LiCl + 2NH_3~ + H_2O~ + CO_2~DSCLiClCO_3~=Li_2CO_3:NH_4Cl = 1:4 (mol)Li_2CO_3LiClNH_4ClNH_4ClLi_2CO_3Li_2CO_3 + 2NH_4Cl = 2LiCl + 2NH_3~ + H_2O~ + CO_2~ NH_4Cl = HCl~ + NH_3~ NH_4Cl = HCl~ + NH_3~ 2HCl + Li_2CO_3 = 2LiCl + H2O~ + CO_2~X1:4mol= Li_2CO_3:NH_4ClLiClLiClLiClAl-LiLiClLi_2CO_3NH_4ClAl-LiLiCl2LiCl-KCl-LiFLiCl-KCl-LiFLiClLiClKClLiCl-LiFLiCl-NaClLiClLiCl-KCl-LiFLiCl-KCl-LiF348 41.4KCl + 57.3LiCl + 1.3LiF (mol)3Li~+, Na~+Li~+Na~+AlLiClLi~+AlNaAl-Li1Li~+, Na~+AlMoLi~+AlNaAl-Li2G_x + G_m = -nFEG_x34Li~+, Na~+Al-Cu, -Al-RECuRELi~+Li~+, Na~+Al-Li Al-Cu-Li, Al-RE-Li5Li~+LiCl-KClAlLiCl0.71 (T = 740 ), 4T720 LiAlD_(Li/Al) = 4.94 * 10~(-5)cm~2s~(-1)Stocks-EinstanD_(Li/Al) = 4.85 * 10~(-5)cm~2s~(-1)51LiF21 A/cm~2Li10w.fAl-Li3 Li
Resumo:
We present photoelectron spectroscopic and low energy electron diffraction measurements of water adsorption on flat Si samples of the orientations (001), (115), (113), (5,5,12) and (112) as well as on curved samples covering continuously the ranges (001)-(117) and (113)-(5,5,12)-(112). On all orientations, water adsorption is dissociative (OH and H) and non-destructive. On Si(001) the sticking coefficient S and the saturation coverage Theta(sat) are largest. On Si(001) and for small miscuts in the [110]-azimuth, S is constant nearly up to saturation which proves that the kinetics involves a weakly bound mobile precursor state. For (001)-vicinals with high miscut angles (9-13 degrees), the step structure breaks down, the precursor mobility is affected and the adsorption kinetics changed. On (115), (113), (5,5,12) and (112), the values of S and Theta(sat) are smaller which indicates that not all sites are able to dissociate and bind water. For (113) the shape of the adsorption curves Theta versus exposure shows the existence of two adsorption processes, one with mobile precursor kinetics and one with Langmuir-like kinetics. On (5,5,12), two processes with mobile precursor kinetics are observed which are ascribed to adsorption on different surface regions within the large surface unit cell. From the corresponding values of S and Theta(sat), data for structure models are deduced. (C) 1997 Elsevier Science B.V.
