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61.
Pulakesh Bera 《Journal of solid state chemistry》2010,183(8):1872-8706
Phase-pure ternary wurtzite Cu-In-S nanocrystals have been synthesized by a simple amine-assisted decomposition of mixed precursor complexes derived from S-methyl dithiocarbazate (SMDTC) at a relatively low temperature without using any external surfactant. The crystal phase, morphology, crystal lattice, and chemical composition of the as-prepared products were analyzed by using X-ray diffraction, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and energy-dispersive X-ray spectroscopy (EDX). The optical properties show the pronounced quantum confinement effect in nanocrystals. A possible growth mechanism has been suggested for the formation of anisotropic wurtzite Cu-In-S It is believed that a combined effect of the chelating amine and precursors containing CH3S unit plays a key role in the formation of the metastable phase of wurtzite Cu-In-S. 相似文献
62.
63.
F. Milde R.A. Römer M. Schreiber V. Uski 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,15(4):685-690
We study the three-dimensional Anderson model of localization with anisotropic hopping, i.e., weakly coupled chains and weakly coupled planes. In our extensive numerical study we identify and characterize the metal-insulator
transition by means of the transfer-matrix method. The values of the critical disorder obtained are consistent with results of previous studies, including multifractal analysis of the wave functions and energy-level
statistics. decreases from its isotropic value with a power law as a function of anisotropy. Using high accuracy data for large system
sizes we estimate the critical exponent as . This is in agreement with its value in the isotropic case and in other models of the orthogonal universality class.
Received 25 October 1999 相似文献
64.
In modern materials science the characterisation of nanostructures is becoming increasingly important. For measurement of the quality of nanoscale multilayer arrangement with high spatial resolution a method is described that is based on the broadening of the spots in the Fourier transformation of transmission electron microscopic images of multilayer cross-sections. Using this method on Si/Ge superlattices with periodic lengths between 4 and 12 nm it could be quantitatively shown that the layer perfection decreases with increasing periodic length. The transition from elastic to plastic deformation between the Si and Ge layers at larger periodic lengths can be the reason for this behaviour. 相似文献
65.
C. -K. Sun J. C. LiangS. P. DenBaarsD. S. Kim Y. D. ChoG. D. Sanders J. SimmonsC. J. Stanton 《Superlattices and Microstructures》2000,27(5-6):593-596
Experiments have shown that ultrafast optical excitation of semiconductors can produce oscillating changes in the optical properties of the material. The frequency of the oscillations in transmission or reflection usually matches one of the phonon modes, typically theq = 0 optical mode. These oscillations are known as coherent phonons. We discuss the role of surfaces and interfaces on the coherent phonon signal. We show that: (1) the coherent phonon signal can be used as a probe of the surface depletion field and (2) multiple interfaces as in a superlattice, can drastically alter the coherent phonon spectrum: screening of the modes in the superlattices is reduced and acoustic modes can now be excited. 相似文献
66.
The negatively charged exciton in double-layer quantum dots 总被引:1,自引:0,他引:1
Wenfang Xie 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,17(3):385-389
The hyperangular equation for charged semiconductor complexes in a double-layer harmonic quantum dot was solved numerically
by using the correlated hyperspherical harmonics as basis functions. By using this method, we have calculated the energy spectra
of the low-lying states of a charged exciton as a function of the radius of the quantum dot and the binding energy spectra
of the ground state as a function of the radius of the quantum dot for a few values of the distance between the vertically
coupled dots and the electron-to-hole mass ratio.
Received 3 December 1999 相似文献
67.
68.
P.Y. Friot P. Turban S. Andrieu M. Piecuch E. Snoeck A. Traverse E. Foy C. Theodorescu 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,15(1):41-50
This study is dedicated to the growth of bcc Mn by molecular beam epitaxy, in order to look at the magnetic properties of
bcc Mn near room temperature. For this purpose, Mn is deposited on bcc MxV1-x(001) alloy lattices (M = Fe or Nb) for which the lattice spacing is tunable by varying the concentration x. We first show that the parameter of the MxV1-x alloy's buffer layers can be adjusted from 2.95 ? to 3.3 ? depending on x and M. Three different structures in Mn films grown on these buffer layers are observed depending on the in-plane spacing
of the initial MxV1-x lattice. Thick Mn films are always found to grow epitaxially in the Mnstructure. For moderate thicknesses larger than 4 atomic planes, Mn grows in an unidentified structure. Finally, up to four
deposited atomic planes, Mn is found to grow in a tetragonal structure close to a bcc one on Fe(001), FexV1-x(001) and NbxV1-x(001) for . This tetragonal structure is shown to be a distorsion of a Mn bcc structure with . Except for ultra-thin Mn films deposited on Fe(001), no macroscopic magnetization is detected in our strained bcc Mn samples.
These results are compared to theoretical predictions.
Received 21 June 1999 相似文献
69.
A series of c-axis oriented BaTiO3/SrTiO3 superlattices with the atomic-scale precision were epitaxially grown on single-crystal SrTiO3(l00) substrates using laser molecular-beam epitaxy (LMBE). A periodic modulation of the intensity of reflection high-energy
electron diffraction (RHEED) in BaTiO3 and SrTiO3 layers was observed and attributed to the lattice-misfit-induced periodic variation of the terrace density in film surface.
The relationship between the second-order nonlinear optical susceptibilities and the superlattice structure was systematically
studied. The experimental and theoretical fitting results indicate that the second-order nonlinear optical susceptibilities
of BaTiO3/SrTiO3 superlattices were greatly enhanced with the maximum value being more than one order of magnitude larger than that of bulk
BaTiO3 crystal. The mechanism of the enhancement of the second-order optical nonlinearity was discussed by taking into account the
stress-induced lattice distortion and polarization enhancement. 相似文献
70.
In the asymptotic limit, the interlayer exchange coupling decays as D-2, where D is the spacer thickness. A systematic procedure for calculating the preasymptotic corrections, i.e., the terms of order D-n with ,is presented. The temperature dependence of the preasymptotic corrections is calculated. The results are used to discuss
the preasymptotic corrections for the Co/Cu/Co(001) system.
Received 7 January 1999 相似文献