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991.
The hole thermal-emission rates and the cross sections for hole capture to the bound states in Ge quantum dots in Si are determined by admittance spectroscopy. The capture cross sections and the activation energies for emission rate are found to be related to each other by the Meyer-Neldel rule with a characteristic energy of 27±3 meV, which does not depend on the quantum-dot size. It is established that the capture cross section changes with temperature following the activation law. The experimental data are evidence of a unified multiphonon mechanism for the activation processes of hole transitions from the Ge quantum dots to the Si valence band and hole capture back into the quantum dots. 相似文献
992.
Intra and intermolecular interactions of heptasulfur imide (S7NH) are investigated in terms of topological properties analyses, such analyses are applied to both experimental (multipole model) and theoretically calculated (DFT and PDFT calculations) charge densities of the isolated molecule and of the crystal. The same analyses are also applied to a multipole model density obtained from theoretically (PDFT) derived structural amplitudes. The covalent bond character of S-N, N-H and S-S bonds are well described in terms of density, ρb, and total energy density, Hb, at the bond critical point rc, though it is clear that the S-S bonds are weaker shared interactions than those of N-H and S-N bonds. Lone pair electron regions of sulfur and nitrogen atoms are revealed as the local charge concentration site from the Laplacian of charge density. The even weaker intermolecular interactions are well characterized; these include the N-H?S hydrogen bonding, N?S binding interactions and S?S binding interactions. All these intermolecular binding interactions are closed-shell interactions. The Laplacian of charge density demonstrates a directional intermolecular binding interaction. The corresponding intermolecular binding energies are derived by MP2/6-311+G(d,p) calculations. Atomic graph of each atom of the molecule is described in detail by the vertices, edges and faces of the polyhedron around the nucleus to illustrate such directional interactions. 相似文献
993.
994.
A. V. Novikov D. N. Lobanov A. N. Yablonsky Yu. N. Drozdov N. V. Vostokov Z. F. Krasilnik 《Physica E: Low-dimensional Systems and Nanostructures》2003,16(3-4):467
The dependence of photoluminescence spectra of structures with GeSi/Si(0 0 1) self-assembled nanoislands on growth temperature has been investigated. It was shown that the redshift of the island-related photoluminescence peak with a decrease of the growth temperature is associated with suppression of Si diffusion in the islands and an increase of Ge content in them. For the first time a photoluminescence signal from SiGe islands was observed at energies much lower than the Ge band gap. The energy position of the island-related photoluminescence peak is well described by the model of optical transition, which is indirect in real space. The photoluminescence signal at 1.55 μm from GeSi/Si(0 0 1) self-assembled islands was obtained up to room temperature. 相似文献
995.
We use methods of nonequilibrium statistical thermodynamics to investigate two dissipative processes in solids. We find the electron energy losses of a particle moving in a planar channeling regime and the sound absorption coefficient in metals under electron impurity scattering. The oscillator model is used to analyze the contribution from the effect of electron entrainment by a moving scattering center to the total dissipated energy. We investigate the frequency and temperature dependence of energy losses and also the dependence of the absorption coefficient on the sound wave vector. 相似文献
996.
CunLiuZHOU YuQingZHOU ZhiYongWANG 《中国化学快报》2003,14(4):355-358
The chemoselective addition of aldehydes in aquoues medium was obtained under mild condition using improved Henry reaction. 相似文献
997.
The protonation and alkylation of cross-conjugated ketones containing a terminal N-methylpyrrole ring takes place at the oxygen atom. Protonation is accompanied by a strong bathochromic shift of the absorption maximum in the electron spectrum, while alkylation leads to ethoxypolymethine salts. The possibility of using these salts for the synthesis of ethoxycyanine dyes was studied. 相似文献
998.
Complexes of Co(II) and Zn(II) with three-membered structures containing 1,3-indanedione, 1,3,4-thiadiazole, and pyridine moieties were obtained. 相似文献
999.
We investigate the scattering problem for a relativistic electron with spin in a Coulomb field in the framework of pseudoclassical mechanics. We obtain an analytic expression for the scattering angle and limiting estimates for the scattering parameters for the spinless and nonrelativistic cases. For small angles, the pseudoclassical model under consideration leads to the well-known quantum-mechanical Mott formula. 相似文献
1000.
Ginzburg B. M. Smirnov A. S. Filatov S. K. Shibaev L. A. Melenevskaya E. Yu. Novoselova A. V. Shepelevskii A. A. 《Russian Journal of Applied Chemistry》2003,76(3):457-459
The structure of aggregates of fullerene C6
0 introduced into films of radical polymethyl methacrylate in the stage of solution preparation was studied by wide-angle X-ray diffraction. 相似文献