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11.
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Ph. Komninou Th. Kehagias A. Delimitis G.P. Dimitrakopulos J. Kioseoglou E. Dimakis A. Georgakilas Th. Karakostas 《Superlattices and Microstructures》2004,36(4-6):509
The structural properties of InN thin films, grown by rf plasma-assisted molecular beam epitaxy on Ga-face GaN/Al2O3(0001) substrates, were investigated by means of conventional and high resolution electron microscopy. Our observations showed that a uniform InN film of total thickness up to 1 μm could be readily grown on GaN without any indication of columnar growth. A clear epitaxial orientation relationship of , was determined. The quality of the InN film was rather good, having threading dislocations as the dominant structural defect with a density in the range of 109–1010 cm−2. The crystal lattice parameters of wurtzite InN were estimated by electron diffraction analysis to be a=0.354 nm and c=0.569 nm, using Al2O3 as the reference crystal. Heteroepitaxial growth of InN on GaN was accomplished by the introduction of a network of three regularly spaced misfit dislocation arrays at the atomically flat interface plane. The experimentally measured distance of misfit dislocations was 2.72 nm. This is in good agreement with the theoretical value derived from the in-plane lattice mismatch of InN and GaN, which indicated that nearly full relaxation of the interfacial strain between the two crystal lattices was achieved. 相似文献
13.
This contribution discusses the phenomena of retrograde condensation of one or two liquids. It w1 be shown that both phenomena can be well understood. Also the relation of retrograde condensation of one liquid phase with the condensation behavior of natural gas will be discussed. Similarly that of two liquid phases with multiple phase behavior occurring in low temperature reservoir fluids will be pointed out. 相似文献
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Th. Friedrich I. Kath A. Moroianu U. Semmelmann 《Journal of Geometry and Physics》1997,23(3-4):259-286
A nearly parallel G2-structure on a seven-dimensional Riemannian manifold is equivalent to a spin structure with a Killing spinor. We prove general results about the automorphism group of such structures and we construct new examples. We classify all nearly parallel G2-manifolds with large symmetry group and in particular all homogeneous nearly parallel G2-structures. 相似文献
16.
Polymer lightguides of PMMA doped with the azo dyes methyl-red and N, N-dihexyl-4-amino-4'-nitro-azobenzene (DHANA) are investigated with respect to their opto-optical properties. The trans-cis photoisomerisation of the dyes leads to reversible polarization-dependent optically induced refractive index changes. The index changes are anisotropic. Birefringence is measured using index matched lightguides. The changes with respect to each polarization are determined by leaky mode spectroscopy and by using a half-integrated interferometer. These changes are intensity dependent and, with a suitable geometry, bistability at low intensities (3 mW/mm3) can be obtained. 相似文献
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Near-infrared laser photoacoustic detection of methane: the impact of molecular relaxation 总被引:1,自引:0,他引:1
A photoacoustic sensor has been developed for trace-gas monitoring using a near-infrared semiconductor laser emitting in the
2ν3 band of methane at 1.65 μm. The apparatus was designed for on-line process control in the manufacturing of the novel low-water-peak
fibres developed for optical telecommunications. The importance of collisional relaxation processes in the generation of the
photoacoustic signal is reported in the particular case of CH4 detection in dry O2 and O2–N2 mixtures. The negative influence of these effects results in a strongly reduced and phase-shifted photoacoustic signal, induced
by a fast resonant coupling between the vibrational states of methane and oxygen, associated with the slow relaxation of the
excited oxygen molecules. An unusual parabolic response of the sensor with respect to the methane concentration has been observed
and is discussed. Finally, the beneficial effect of several species, including water vapour and helium, acting as a catalyst
to hasten the relaxation of the CH4–O2 system, is demonstrated.
PACS 42.62.Fi; 33.20.Ea; 34.50.Ez 相似文献
19.
The dependence of the formation of a p-n or p-p+ junction in semiconducting TiO2 as a function of various parameters is investigated through a computer model. The effect of the polarizing conditions on
the I–V characteristics is also discussed and related to experimental results.
Paper presented at the 3rd Euroconference on Solid State Ionics, Teulada, Sardinia, Sept. 15–22, 1996 相似文献
20.
We present anO(p · n) algorithm for the problem of finding disjoint simple paths of minimum total length betweenp given pairs of terminals on oriented partial 2-trees withn nodes and positive or negative arc lengths. The algorithm is inO(n) if all terminals are distinct nodes. We characterize the convex hull of the feasible solution set for the casep=2.We gratefully acknowledge the referee's many helpful suggestions to improve the presentation of this paper. 相似文献