| 1. |
- Arnaudov, B., et al.
(författare)
-
Free-to-bound radiative recombination in highly conducting InN epitaxial layers
- 2004
-
Ingår i: Superlattices and Microstructures. - : Elsevier BV. - 0749-6036 .- 1096-3677. ; 36:4-6, s. 563-571
-
Tidskriftsartikel (refereegranskat)abstract
- We present a theoretical simulation of near-band-edge emission spectra of highly conducting n-InN assuming the model of 'free-to-bound' radiative recombination (FBRR) of degenerate electrons from the conduction band with nonequilibrium holes located in the valence band tails. We also study experimental photoluminescence (PL) spectra of highly conducting InN epitaxial layers grown by MBE and MOVPE with electron concentrations in the range (7.7 × 1017-6 × 1018) cm-3 and find that the energy positions and shape of the spectra depend on the impurity concentration. By modeling the experimental PL spectra of the InN layers we show that spectra can be nicely interpreted in the framework of the FBRR model with specific peculiarities for different doping levels. Analyzing simultaneously the shape and energy position of the InN emission spectra we determine the fundamental bandgap energy of InN to vary between Eg = 692 meV for effective mass mn0 = 0.042m0 and Eg =710 meV for mn0 = 0.1m0. © 2004 Elsevier Ltd. All rights reserved.
|
|
| 2. |
- Darakchieva, Vanya, 1971-, et al.
(författare)
-
Deformation potentials of the E1 (TO) and E2 modes of InN
- 2004
-
Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 84:18, s. 3636-3638
-
Tidskriftsartikel (refereegranskat)abstract
- The determination of deformation potentials of E1(TO) and E 2 modes of InN were discussed. The deformation potentials were evaluated for two sets of stiffness constants using x-ray diffraction, IR spectroscopic ellipsometry (IRSE), Raman scattering, and Grüneisen parameter values. The InN layer were grown on GaN buffer layers on (0001) sapphire by molecular beam epitaxy. It was found that the strain-free values of the InN E1(TO) mode was 477.9 cm-1 and 491.9 cm -1 for the E2 modes.
|
|
| 3. |
- Darakchieva, Vanya, et al.
(författare)
-
Infrared ellipsometry and Raman studies of hexagonal InN films : Correlation between strain and vibrational properties
- 2004
-
Ingår i: Superlattices and Microstructures. - : Elsevier BV. - 0749-6036 .- 1096-3677. ; 36:4-6, s. 573-580
-
Tidskriftsartikel (refereegranskat)abstract
- The vibrational properties of InN films with different strain have been studied using Infrared ellipsometry and Raman scattering spectroscopy. We have established a correlation between the phonon mode parameters and the strain, which allows the determination of the deformation potentials and the strain-free frequencies of the InN E1(TO) and E2 modes. The LO phonons and their coupling to the free-carrier plasmon excitations are also discussed in relation to the carrier concentration in the films. © 2004 Elsevier Ltd. All rights reserved.
|
|
| 4. |
- Fu, Ying, 1964, et al.
(författare)
-
Photoluminescence spectra of doped GaAs films
- 2004
-
Ingår i: Applied Physics A. - : Springer Science Business Media. - 0947-8396 .- 1432-0630. ; 79:3, s. 619-623
-
Tidskriftsartikel (refereegranskat)abstract
- We have studied the dependence of the photoluminescence (PL) spectrum on the doping level and the film thickness of n-GaAs thin films, both experimentally and theoretically. It has been shown theoretically that modification of the PL spectrum of p-type material by p-type doping is very small due to the large valence-band hole effective mass. The PL spectrum of n-type material is affected by two factors: (1) the electron concentration which determines the Fermi level in the material; (2) the thickness of the film due to re-absorption of the PL signal. For the n-type GaAs thin films under current investigation, the doping level as well as the film thickness can be very well calibrated by the PL spectrum when the doping level is less than 2 x 10(18) cm(-3) and the film thickness is in the range of the penetration length of the PL excitation laser.
|
|
| 5. |
- Jiang, Jun, et al.
(författare)
-
Length dependence of coherent electron transportation in metal-alkanedithiol-metal and metal-alkanemonothiol-metal junctions
- 2004
-
Ingår i: Chemical Physics Letters. - : Elsevier BV. - 0009-2614 .- 1873-4448. ; 400:4-6, s. 336-340
-
Tidskriftsartikel (refereegranskat)abstract
- We have applied the elastic-scattering Green's function theory to study the coherent electron transportation processes in both metal-alkanedithiol-metal (gold-[S(CH2)(n)S]-gold, n = 8-14) and metal-alkanemonothiol-metal (gold-[H(CH2)(n)S]-gold, n = 814) at the hybrid density functional theory level. It is shown that the current decreases exponentially with the molecular length. At the low temperature limit the electron decay rate, beta, for alkanedithiol junction is found to be around 0.30/CH2 at 1.0 V bias, much smaller than the calculated value of 0.60/CH2 for alkanemonothiol junction. The decay rate for alkanedithiol junction at the room temperature is neither sensitive to the activation of the Au-S stretching vibrational mode nor to the external bias. The calculated current-voltage characteristics and decay rates for both junctions are in excellent agreement with the corresponding experimental results.
|
|
| 6. |
- Sun, S. G., et al.
(författare)
-
Synthesis of a series of rhenium(I) bipyridyl complexes as photosensitive dyes
- 2004
-
Ingår i: Gaodeng xuéxiào huàxué xuébào. - 0251-0790. ; 25:5, s. 820-822
-
Tidskriftsartikel (refereegranskat)abstract
- In order to study the effects of the substituted groups on the properties of the complexes, a series of rhenium ( I ) 2, 2'-bipyridyl complexes [fac- (4, 4'-di-COOEt-bpy) Re (CO)(3) (X-pyridine) PF6], where bpy is 2,2'-bipyridine and X is 4-methyl, 3-hydroxy, 4-hydroxy, 4-amino, or H, were synthesized with a yield more than 90%, and characterized by H-1 NMR, C-13 NMR, 2D-NMR (H-1-H-1 COSY, HMBC, HSQC), ESI-MS and HRMS. The delta(H) values on the X-pyridine ring were shifted to up-field in H-1 NMR and the MLCT absorbance maxima were red-shifted as the X groups became more electron-donating from H to 4-methyl, 4-hydroxy or 4-amino. The ESI-MS and FIRMS showed the mono-charged peaks and their isotopic peaks of the complexes. The absorption maximum of id(X=4-amino) is 20 nm longer than that of 1e(X=H). It might be used to broaden the absorption range of solar cells.
|
|
