324 resultados para Avidina, Biotina, bioconiugazione, complessi luminescenti, Iridio(III)
Resumo:
A theoretical model accounting for the macropolarization effects in wurtzite III-V nitrides quantum wells (QWs) is presented. Energy dispersions and exciton binding energies are calculated within the framework of effective-mass theory and variational approach, respectively. Exciton-associated transitions (EATs) are studied in detail. An energy redshift as high as 450 meV is obtained in Al0.25GaN0.75/GaN QWs. Also, the abrupt reduction of optical momentum matrix elements is derived as a consequence of quantum-confined Stark effects. EAT energies are compared with recent photoluminescence (PL) experiments and numerical coherence is achieved. We propose that it is the EAT energy, instead of the conduction-valence-interband transition energy that is comparable with the PL energy. To restore the reduced transition rate, we apply an external electric field. Theoretical calculations show that with the presence of the external electric field the optical matrix elements for EAT increase 20 times. (C) 2001 American Institute of Physics.
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Point defects in III-V compound semiconductors were analyzed systematically in this paper. The effects of substitutes, antisites, interstitials, and vacancies on lattice parameters in III-V compound semiconductors were calculated with a simple model. The formation energies of vacancies in compound semiconductors can be obtained by this calculation. A practical technique established on this model has been utilized for measuring the stoichiometry in GaAs. The relationship between stoichiometry and deep level centers in GaAs was also investigated.
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We report experiments on high de current stressing in commercial III-V nitride based heterojunction light-emitting diodes. Stressing currents ranging from 100 mA to 200 mA were used. Degradations in the device properties were investigated through detailed studies of the current-voltage (I-V) characteristics, electroluminescence, deep-level transient Fourier spectroscopy and flicker noise. Our experimental data demonstrated significant distortions in the I-V characteristics subsequent to electrical stressing. The room temperature electro-luminescence of the devices exhibited a 25% decrement in the peak emission intensity. Concentration of the deep-levels was examined by deep-level transient Fourier spectroscopy, which indicated an increase in the density of deep-traps from 2.7 x 10(13) cm(-3) to 4.2 x 10(13) cm(-3) at E-1 = E-C - 1.1 eV. The result is consistent with our study of 1/f noise, which exhibited up to three orders of magnitude increase in the voltage noise power spectra. These traps are typically located at energy levels beyond the range that can be characterized by conventional techniques including DLTS. The two experiments, therefore, provide a more complete picture of trap generation due to high dc current stressing.
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The kinetics of MOCVD GaInAsSb and AlGaAsSb was studied by the growth rate as a function of growth temperature and partial pressure of III and V MO species. The diffusion theory was used to explain the mass transport processes in MOCVD III-V quaternary antimonides. On the basis of the discussion about their growth kinetics and epilayer properties, the good quality multi-epilayers of these two quaternary antimonides and their photodetectors and arrays with wavelength of 1.8 similar to 2.3 mu m and detectivities of D* > 10(9) cm Hz(1/2) W-1 were obtained.
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The room temperature Raman spectra of the Ga(0.5)Al(0.5)AS and the In0.52Al0.48As epilayer grown on [n11]-oriented substrates were measured in various back scatterng geometries, The relative intensity of TO modes and LO modes in those samples shows a regular Variation with differently oriented substrates in the experiments. By comparing experimental data with Raman scattering selection rules for the zincblende structure epilayer grown on [n11]-oriented substrates, it was found that the present calculations are in good agreement with the experimental results.
Resumo:
We report experiments on hot-electron stressing in commercial III-V nitride based heterojunction fight-emitting diodes. Stressing currents ranging from 100 mA to 200 mA were used. Degradations in the device properties were investigated through detailed studies of the I-V characteristics, electroluminescence, Deep-Level Transient Fourier Spectroscopy and flicker noise. Our experimental data demonstrated significant distortions in the I-V characteristics. The room temperature electroluminescence of the devices exhibited 25% decrement in the peak emission intensity. Concentration of the deep-levels was examined by measuring the Deep-Level Transient Fourier Spectroscopy, which indicated an increase in the density of deep-traps from 2.7 x 10(13) cm(-3) to 4.21 x 10(13) cm(-3) at E-1 = E-C - 1.1eV. The result is consistent with our study of 1/f noise, which exhibited up to three orders of magnitude increase in the voltage noise power spectra. Our experiments show large increase in both the interface traps and deep-levels resulted from hot-carrier stressing.
Resumo:
The qualities of GaSb substrates commonly used for the preparation of III-V antimonide epilayers were studied before and after growing GaInAsSb multi-layers by MOCVD using PL, FTIR and DCXD together with the electrical properties and EPD value. The correlation between the substrate qualities and epilayer properties was briefly discussed. The good property epilayers of GaInAsSb and, then, the high preformance of 2.3 um photodetectors were achieved only using the good quality GaSb wafers as the substrates.
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GHzhangdi
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Various techniques on the growth of self-assembled compound semiconductor nano-structures (quantum dots, QDs) have been tried to enhance the controlling on size, density, emitting wavelength, uniformity in size and ordering in location of the QDs. Optimized growth conditions have been used in the application of the QD materials in opto-electronic devices. High-power long-lifetime quantum-dot laser-diodes (QD-LDs) emitting near 1 mu m, QD-LDs emitting in red-light range, 1.3 mu m QD-LDs on GaAs substrate and quantum-dot super-luminescent diodes (QD-SLDs) have successfully been achieved.
Resumo:
1--3-[C8mim]PF6N1923N1923/ILN1923/ILN1923/ILN1923/IL [C8mim]PF62-2-DEHEHPIV[C8mim]PF6IVIVCe4+Ce(NO3)62-PF6[C8mim]2Ce(NO3)6IVDEHEHP[C8mim]PF6IVDEHEHPIVDEHEHP/IL99.9%CeF3
Resumo:
HEHEHPCyanex272pHH~+NH_4~+K
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Cr(III)Cr(VI)PtPbO_2Cr(VI)[H_2SO_4][SO_4~=]Cr_2(SO_4)_3Cr(VI)Pt = a + 0.25 log i_2 - 0.23 log [Cr(III)] = a' + 0.48 log i_2 - 0.44 log [Cr(III)]Tafel2.303 RT/F ( 0.5)PtCr(VI)Cr(II)H_2O (OH)_(ad) + H~+ + e~- 2(OH)_(ad) (O)_(ad) + H_2O 2(O)_(ad) O_2 (OH)_(ad) + [Cr(H_2O)_6]~(3+) (CrO_2)_(ad) + 3H~+ + 5H_2O (CrO_2)_(ad) + H_2O (CrO_3~-)_(ad) + 2H~+ + e~- (CrO_3~-)_(ad) + H_2O HCrO_4~- + H~+ + e~- 2HCrO_4~- <-> Cr_2O_7~(2-) + H_2O [H_2SO_4][SO_4~(2-)]Cr_2(SO_4)_3Cr(VI)-PbO_2 = a + 0.28 log i_2 - 0.30 log [Cr(III)] = a' + 0.55 log i_2 - 0.51 log [Cr(III)]Tafel2.303RT/F ( approx= 0.5)PbO_2PtCr(VI)PbO_210 Kcal mol~(-1)pH[H_2SO_4]Cr(VI)[H_2SO_4][SO_4~(2-)]Cr_2(SO_4)_3PbO_2CadCd1-2CdCdSO_4~(2-)HCrO_4~-, Cr_2O_7~-[_((SO_4))~((H_2O)_2) Cr_((SO_4))~((OH)_2) Cr_((SO_4))~((OH_2)_2)]~(2-)PbO_2Cr(VI)H_2O (OH)_(ad) + H~+ + e~- (OH)_(ad) + H_2O (O)_(ad) + H_3O~+ + e~- 2(O)_(ad) O_2 [Cr(H_2O)_6]~(3+) + (O)_(ad) (CrO_3~-)_(ad) + 4H~+ + 4H_2O (CrO_3~-)_(ad) + H_2O HCrO_4~- + H~+ +e~- 2HCrO_4~- <-> Cr_2O_7~(2-) + H_2O.
