Search

Quantum nanostructures ( QNSs), due to their widespread and attractive physical, optical, and electronic properties, have been at the center of attention of many nanoscience and nanotechnology researches. In order to predict the electro-mechanical behavior of QNSs, accurate determination of the electro-elastic fields induced by quantum wells ( QWs), quantum wires ( QWRs), and quantum dots ( QDs) in such nanostructures would be of great importance and particular interest. In this study, by utilization of the electro-mechanical eigenfield concept in conjunction with the Fourier series technique, an analytical solution is presented which gives the electro-elastic fields induced by one-, two-, and three-dimensional periodic distribution of QWs, QWRs, and QDs, respectively. This methodology takes into account the electro-mechanical couplings of elastic and electric fields within the piezoelectric barrier as well as the interaction between periodically grown QWRs and QDs. The latter would be so important since the density of the periodically grown QNSs will have significant effects on the induced electro-elastic fields within both the QNSs and the surrounding barrier; this issue is addressed precisely in the present study by measuring the induced electro-elastic fields due to different periodicities of pyramidal QDs. Furthermore, the current formulation is capable of treating arbitrary geometries of QWRs and QDs which makes the solution more interesting and powerful. (C) 2015 Published by Elsevier Ltd.

2 pages, 1 figure.-- PACS nrs.: 73.63.Nm; 72.25.Dc; 71.70.Ej.-- Available online Oct 1, 2007.-- Issue title: "17th International Conference on Electronic Properties of Two-Dimensional Systems" (Genova, Italy, Jul 15-20, 2007). A local spin–orbit (SO) interaction of Rashba type induces the appearance of a static spin distribution in a quantum wire when a steady current is flowing along the wire. We obtain the density and spin distributions using matching of the wire's propagating and evanescent modes at the SO interfaces. A nonvanishing net spin lying in the two-dimensional (2D) wire plane and pointing perpendicularly to the wire is obtained. The relevance of the wire's evanescent modes is stressed. This work was supported by Grant FIS2005-02796 and by the Spanish "Ramón y Cajal" program.

arXiv:cond-mat/0512618v1, Using X-ray diffraction Ghose et al. [S.K. Ghose, I.K. Robinson, P.A. Bennett, F.J. Himpsel, Surf. Sci. 581 (2005) 199] have recently produced a structural model for the quantum-wire surface Si(5 5 3)–Au. This model presents two parallel gold wires located at the step edge. Thus, the structure and the gold coverage are quite different from previous proposals. We present here an ab initio study using density functional theory of the stability, electronic band structure and scanning tunneling microscopy images of this model., This work was supported by the Basque Departamento de Educación, the UPV/EHU (Grant No. 9/UPV 00206.215-13639/2001), the Spanish Ministerio de Educacón y Ciencia (Grant No. FIS2004-06490-C3-02), and the European Network of Excellence FP6-NoE “NANOQUANTA” (500198-2). SR also acknowledges support from the Magnus Ehrnroot Foundation.

5 páginas, 4 figuras, 1 tabla.-- 3rd Ibero American workshop on Nanostructures for applications to Micro and Optoelectronics., We report here in situ measurements of stress evolution during molecular beam epitaxy growth of InAs/InP (001) quantum wires. The obtained results provide the necessary information to understand why quantum wires instead of quantum dots are formed in this heteroepitaxial system: a strong stress anisotropy along 110 directions is responsible for it. Moreover, during quantum wires growth As/P exchange reactions take place, which determine the total amount of InAs incorporated in the nanostructures and then their optical properties. In situ stress measurements have also been used to study the exchange process and they have allowed us to calculate the quantity of InAs that enters into the lattice because of it., This work has been supported by the European Commission Growth program NANOMAT project, contract no. G5RD-CT-2001-00545 and by Spanish MCYT under NANOSELF project TIC2002-04096-C03-03.

3 páginas, 2 figuras.-- PACS: 73.21.Hb; 78.55.Cr; 78.67.Lt.-- Proceedings of the International Conference on Superlattices, Nano-structures and Nano-devices ICSNN 2002., Multilayer structure containing vertically stacked InAs/InP self-assembled quantum wires (QWR) have been successfully grown by molecular beam epitaxy. We have found that spacer layer thickness fully determines the structural and optical properties ofthe multilayer structure, being observed a strong improvement ofthe homogeneity and uniformity ofthe QWR stacks in the case ofan appropriate layer spacing., This work has been supported by the Spanish CICYT under the project no. TIC99-1035-C02 and European Commission GROWTH program NANOMAT project, Contract no. G5RD-CT-2001- 00545.

2 páginas, 2 figuras.-- Proceedings of the International Conference on Superlattices, Nano-structures and Nano-devices ICSNN 2002., When depositing by Molecular Beam Epitaxy a few InAs monolayers onto a (0 0 1) InP substrate, one can obtain an array of self-assembled wires at a nanometer scale. We have performed grazing incidence diffraction anomalous fine structure experiments on capped InAs/InP quantum wires (QWrs) to investigate their structural properties. Elastic strain relaxation has been simulated by the finite differences method., We acknowledge the CICYT project MAT99-0847, the EC growth program contract G5RD-CT-2001- 00545 and also the sta# of the BM02-ESRF CRG beamline.

10 páginas, 8 figuras, 1 tabla.-- PACS: 61.10.)I; 61.10.Ht; 68.65.)k.-- Comunicación presentada al E-MRS 2002 Spring Meeting celebrado en Estrasburgo (Francia) del 18 al 21 de Junio de 2002., We have studied self-organized quantum wires of InAs, grown by molecular beam epitaxy onto a InP(0 0 1) substrate, by means of grazing incidence diffraction anomalous fine structure (DAFS). The equivalent quantum wires thickness is 2.5 monolayers. We measured the (4 4 0) and (4 2 0) GIDAFS spectra, at the As K-edge, keeping the incidence and exit angles close to the InP critical angle. The analysis of both the smooth and oscillatory contributions of the DAFS spectrum, provide valuable information about composition and strain inside the quantum wires and close to the interface. We also show preliminary results on InAs wires encapsulated by a 40 Å thick InP capping layer, suggesting the DAFS capability of probing different iso-strain regions of the wires., One of the authors (M.G.P.) is pleased to acknowledge support from the ‘‘Universit e Joseph Fourier’’ and the ‘‘Centre National pour la Recherche Scientifique’’. This work was also supported by the LEAMANESEuropean Agreement, theCICYTprojects no. MAT99-0847 and by the NANOMAT project of the EC growth programme contract no. G5RDCT- 2001-00545.

A system able to produce entangled two-electron states is proposed and studied by means of numerical simulations. The basic device consists of a couple of semiconductor quantum wires in which single electrons are injected and propagated coherently. Coulomb coupling between two electrons in two different wires arises in a region where the wires get close to each other. The strength of this interaction can be tuned with a proper design of the system geometry. It is shown that it is possible to create the four entangled Bell states for the two-particle wave function.

12 páginas, 4 figuras.-- PACS: 68.35.-p, 85.30.Vw, 68.35.Ct, 81.15.Hi.-- PDF pre-print., We report in situ and in real time quantitative measurements of stress along [1 1 0] and directions during the formation of InAs/InP(0 0 1) quantum wires (QWr) and consequent stress relaxation. Results show a strong stress anisotropy due to the distortion of As–In bonds along [1 1 0] and As–As dimerization along [1 1 0]. This anisotropy is claimed to be the origin of QWr formation instead of self-assembled quantum dots. Anisotropic stress relaxation associated to QWr formation is shown to be characteristic of heteroepitaxial systems involving different group V elements grown by MBE under group V stabilized surface (2×4 reconstruction)., The authors wish to acknowledge to the Spanish “CICYT” for financial support under the project No. TIC99-1035-C02. One of the authors, M.U. González, thanks the Consejería de Educación y Cultura de la Comunidad de Madrid for financial support.