12 al 15 de enero de 2010 Valparaíso Chile. Contribuciones

Transcripción

1 12 al 15 de enero de 2010 Valparaíso Chile Contribuciones

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3 Tabla de Contenido Relatores Mini-Cursos... 4 Tópicos Mini-Cursos... 4 Expositores Invitados... 5 Comité Organizador... 6 Programa... 7 Mini - Cursos... 9 Atomic Contacts and Mesoscopic Superconductivity...11 Predicting and understanding phenomena in nanostructures...12 Growth and Applications of Nanomaterials...13 Electrical and Magnetic properties of graphene...14 Microscopia Electronica de nanostructuras: avances recientes...15 Time-dependent transport in carbon-based materials...16 Charlas Oxidation of metals...19 Spin excitations in metallic ultrathin films...20 Magnetization Reversal in Nanodots...21 Modificación de superficies por bombardeo de iones altamente cargados...22 Conical carbon nanostructures...23 A taste of photonics : plasmon polaritons in 1D heterostructures with lefthanded materials...24 Estudio de la Dinámica de Nucleación y ensamble de Nanotubos de Carbono...25 Modelización de la interacción Coulombiana en nanoestructuras...26 Transporte electrónico en sistemas compuestos por nanocintas de grafeno...27 Structure and Composition of Ultrathin Films...28 Structure and magnetic properties of ultrathin Ni films grown on Pd (100)...29 Moléculas biológicas para aplicaciones nanotecnológicas...30 Poster Índice de autores

4 Relatores Mini-Cursos Cristian Urbina, Quantronics Group, Francia Miguel Jose Yacamán, University of Texas at Austin, USA Luis Brey, Instituto de Ciencia de Materiales de Madrid, España Claudia Gomes da Rocha, Technische Universitat Dresden, Alemania Helio Chacham, Universidade Federal de Minas Gerais, Brasil Rodrigo Gribel Lacerda, Universidade Federal de Minas Gerais, Brasil Tópicos Mini-Cursos Contactos atómicos y superconductividad mesoscópica Microscopía Electrónica de nanostructuras : avances recientes Propiedades eléctricas y magnéticas de grafeno Transporte dependiente del tiempo en materiales basados en carbono Predicción y comprensión de fenómenos en Nanoestructuras Crecimiento y aplicaciones de Nanomateriales 4

5 Expositores Invitados Alejandro León, Universidad Diego Portales, Santiago, Chile Estudio de la Dinámica de Nucleación y ensamble de Nanotubos de Carbono Antonio Tavares da Costa Jr., Univ. Fed. Fluminense, RJ, Brasil Excitaciones de spin en películas metálicas ultradelgadas Carolina Parra, Universidad Santa María, Valparaíso, Chile Evidencia de correlación entre magnetismo y estructura para láminas ultradelgadas de Ni crecidas sobre Pd(100) Clara González-Santander, Univ. Complutense, Madrid, España Modelización de la interacción Coulombiana en nanoestructuras Dora Altbir, Universidad de Santiago de Chile, Santiago, Chile Propiedades magnéticas de nanoestructuras con simetría cilíndrica Eldrid Svasand, Universidad Santa María, Valparaíso, Chile Conos de carbon nanostructurados Judit Lisoni, Universidad de Chile, Santiago, Chile Cómo se oxidan los metales? Luis Rosales, P. Univ. Católica de Valparaíso, Valparaíso, Chile Transporte electrónico en sistemas compuestos por nanocintas de grafeno Luiz E. Oliveira, Universidad de Campinas, SP, Brasil Fotónica en nanoestructuras Marcos Flores, Universidad de Chile, Santiago, Chile Modificación de superficies por bombardeo de iones altamente cargados Torgny Gustafsson, Rutgers University, NJ, USA Estructura y Composición de Películas Ultradelgadas Valeria Del Campo, Universidad Santa María, Valparaíso, Chile Moléculas biológicas para aplicaciones nanotecnológicas 5

6 Comité Organizador Mónica Pacheco Universidad Técnica Federico Santa María (UTFSM), Valparaíso Pedro Orellana Universidad Católica del Norte (UCN), Antofagasta Patricio Häberle Universidad Técnica Federico Santa María (UTFSM), Valparaíso Zdenka Barticevic Universidad Técnica Federico Santa María (UTFSM), Valparaíso Rodrigo Segura Universidad de Valparaíso (UV), Valparaíso Álvaro Núñez Universidad de Chile (UChile), Santiago 6

7 Programa Inicio Martes 12 Miércoles 13 Jueves 14 Viernes 15 9:30 Registro Participantes y Apertura MIGUEL J. YACAMAN MIGUEL J. YACAMAN 10:20 CRISTIAN URBINA CRISTIAN URBINA CRISTIAN URBINA RODRIGO LACERDA 11:10 CAFÉ 11:30 LUIS BREY LUIS BREY LUIS BREY RODRIGO LACERDA 12:20 MIGUEL J. YACAMAN HELIO CHACHAM HELIO CHACHAM ANTONIO COSTA 13:10 ALMUERZO 15:00 LUIZ OLIVEIRA CLAUDIA ROCHA CLAUDIA ROCHA JUDIT LISONI 15:50 LUIS ROSALES MARCOS FLORES DORA ALTBIR TORGNY GUSTAFSSON 16:20 CAFÉ CAFÉ CAFÉ CLAUSURA 16:40 ALEJANDRO LEON CAROLINA PARRA 17:10 CLARA GONZALEZ SESION POSTER ELDRID SVASAND 17:40 VALERIA DEL CAMPO 18:00 ASADO 7

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11 Atomic Contacts and Mesoscopic Superconductivity C. Urbina QUANTRONICS Group, SPEC/IRAMIS/CEA-Saclay, Gif-sur-Yvette, FRANCE address corresponding author: In this set of lectures I will describe an ensemble of transport experiments that probe quantitatively the description of a quantum coherent conductor in terms of transmission channels, a concept at the foundations of the field of mesoscopic physics. These experiments are performed on the simplest of the conductors, namely a one-atom contact between two metallic banks, obtained using the microfabricated breakjunction technique (see Figure 1). In particular we will address the situation in which the banks are superconducting. First, the basic elements of the scattering theory of transport will be introduced [1-2]. Then we will discuss the key concept of Andreev reflection, the microscopic mechanism coupling in a metal the dynamics of electrons and holes and leading to superconductivity [3]. By putting together these concepts both the dissipative current and the supercurrent flowing through any particular structure can be calculated. Using these results, we will show that the number of current carrying modes through a single-atom contact is determined by its number of valence orbitals. Because the transmission coefficients of this small number of conduction channels can be both measured and tuned in-situ, a direct comparison between theory and experiment is possible for any transport property for which a mesoscopic model, i.e. a description in terms of transmissions, is available [4-5]. As a first example, we will detail this comparison for the problem of quantum fluctuations of the current (shot-noise), both in the normal and in the superconducting state. Then, we will address the Josephson effect, and present its modern description in terms of Andreev bound states [6]. Figure 1. Scanning electron micrograph of a suspended aluminium microbridge. This structure is fabricated on top of an elastic substrate, which is bent until the bridge breaks. It is then possible to bring back the two resulting electrodes, with subatomic resolution, until a one atom contact is formed. References [1] Yuli V. Nazarov and Yaroslav M. Blanter, Quantum Transport (Cambridge University Press, 2009). [2] S. Datta : Electronic transport in Mesoscopic systems ( Cambridge University Press, 1997). [3] S. Datta, P. Bagwell, and M.P. Anatram, Phys. Low-Dim. Struct., 3, 1 (1996). [4] N. Agraït, A. Levy Yeyati, and J. M. van Ruitenbeek, Phys. Rep. 377, 81 (2003) and references therein. [5] Ph.D. Thesis of R. Cron, M. Chauvin, B. Huard and Q. Le Masne, available at: dex.htm or [6] M. L. Della Rocca et al, Phys. Rev. Lett. 99, (2007). 11

12 Predicting and understanding phenomena in nanostructures Helio Chacham Depto. de Física, Universidade Federal de Minas Gerais, C. P. 702, Belo Horizonte, MG, Brazil address: The investigation of properties of nanostructures has been an exciting subject for both experimentalists and theorists. For experimentalists, the development of new characterization and nanofabrication techniques allowed the synthesis and the study of a wide range of new, nano-structured materials. For theorists, the development of first-principles techniques and the availability of high-performance processors allowed the prediction of new phenomena in nanostructures, sometimes years before they can be experimentally investigated. I will talk about such interaction between theory an experiment, regarding the investigation of nanotubes and nanoparticles. Since carbon nanotubes were first synthesized in 1991, they have attracted an increasing interest due to their electronic and mechanical properties. Concerning electronic properties, they can be either metallic or semiconductor, depending on their diameter and specific structure (chirality). Concerning the mechanical properties, theoretical and experimental results predict a high Young modulus for carbon nanotubes, comparable to or greater than that of diamond. In contrast, carbon nanotubes are very flexible, and can also be flattened with atomic force microscopy (AFM) tips. Several years ago, we predicted [1], using first-principles calculations, that a semiconductor nanotube could become metallic if flattened (radially compressed) by an AFM tip. We also predicted a universal-type behavior in the mechanical response of the flattened nanotube. Such predictions remained untested for several years. Recently, both phenomena were verified experimentally in our department, in works that involved collaborations between experimentalists and theorists [2,3]. The other subject of my talks will regard to the use of metallic nanoparticles as artificial atoms in the assembly of new types of crystals and materials. These new materials have large voids (empty spaces) between the nanoparticles that can be filled with a variety of molecules (see figure below). We have performed theoretical studies on these materials, explaining experimentally observed phenomena. Figure 1. Periodic assembly of ligand-stabilized Au nanoparticles, doped with PF 6. References [1] M. S. C. Mazzoni and H. Chacham, Appl. Phys. Lett. 76, 1561 (2000). [2] A. P. M. Barboza, H. Chacham and B.R.A. Neves, Phys. Rev. Lett. 102, (2009). [3] A. P. M. Barboza, A.P. Gomes, B.S. Archanjo, P.T. Araujo, A. Jorio, A.S. Ferlauto, M.S.C. Mazzoni, H. Chacham and B.R.A. Neves, Phys. Rev. Lett. 100, (2008). 12

13 Growth and Applications of Nanomaterials Rodrigo Gribel Lacerda 1 Depto. de Física, Universidade Federal de Minas Gerais, Av. Antonio Carlos, 6627, Belo Horizonte, Brazil rlacerda@fisica.ufmg.br One-dimensional structures, such as nanorods and nanowires, have become important building blocks of nanodevices and integrated nanosystems [1]. A wide variety of nanostructured semiconductors materials (Si, Ge and III-V semiconductors) and oxides (Cu x O, ZnO, TiO 2, SnO2, etc.) have been the focus of intense studies in the last years. Different approaches, such as vapor liquid solid (VLS), vapor solid (VS) growth, template mediated growth methods, among others, have been used for the preparation these one-dimensional nanostructures [2,3]. In this school, I will focus on aspects concerning the growth, device fabrication and applications such as field effect transistors and photodetectors of nanowire systems specially ZnO nanowires. For instance, Zinc oxide has proven to be a quite interesting material with properties like piezoelectricity, high energy direct gap (3.37 ev), high optical and luminescent activity. I will present a comprehensive picture of the precise mechanism of ZnO vaporsolid-solid (VSS) nanowire growth at low temperatures and gives the fundamental reasons responsible [3]. We demonstrate by using a combination of synchrotron x-ray diffraction and high resolution transmission electron microscopy that the growth dynamics at low temperatures is not governed by the well-known VLS mechanisms. Based on the Au-Zn phase diagram, temperature measurement and temperature size effects, we show that growth occurs via VSS. The precise composition of the Au-Zn catalyst nanoparticle has been determined to be γ- AuZn. Furthermore, we experimentally observe that there is an indication of an epitaxial relationship between the ZnO nanowires and the γ-auzn seed particle. We believe that these results are not only important for the understanding of ZnO nanowire growth but could also have significant impact on the understanding of growth mechanisms of other nanowire systems [3]. It is well known due to its direct band gap that Zinc oxide has a great potential to be used as a ultra-violet photodetector. I will present an integrated ZnO field effect transistor photodetector where by applying a gate voltage we can modulate the absorption of the material and hence its photocurrent. By using this effect, we are able to tune the wavelength of the absorbed photons down to 372 ± 2 nm making a sharp UV detector at this wave-length. The transistors were built in back gate architecture and had shown a n- type behavior with an on/off gain of about Low temperature transport measurements were performed to probe the activation energy for different gate voltages. Based on those results, we will present a model to explain the modulation that allows photocurrent control of the transistor. We believe that this new architecture can have an important impact on the application for ZnO and other types of nanowire transistors as photodetectors. References 1. X. F. Duan et al., Nature 421, (2003). 2. K. S. Shankar et al., Materials Science & Engineering C-Biomimetic and Supramolecular Systems 25, (2005). 3. L. C. Campos et al, Adv. Mater. 20, 149 (2008). 13

14 Electrical and Magnetic properties of graphene Luis Brey Instituto de Ciencia de Materiales de Madrid, CSIC, Cantoblanco, Madrid SPAIN address In the three talks, I will describe some properties of graphene. The tittles and abstracts of the three presentations are the following: Electronic band structure of graphene. Dirac equation and experimental consequences. Graphene is a two dimensional allotrope of carbon; a sheet of carbon atoms each with three covalently bonded nearest neighbours. Recently graphene has been isolated and it is possible to study experimentally its structural, electric and magnetic properties. In this presentation, I will review very briefly some general properties of graphene. First, I will introduce the tight-binding Hamiltonian able to describe the graphene band structure. From this Hamiltonian I will derive the Dirac equation that governs the low energy and long distance properties of graphene. The eigenvalues of the Dirac equation depend linearly on the momentum of the electron and the corresponding wave functions have a chiral behaviour. Finally, we review some experiments (ARPES, electronic transport, QHE) that confirm that the Dirac equation describes appropriately the low energy properties of graphene. RKKY interaction in graphene and vacancy induced magnetism in graphene. In this talk, I will analyze RKKY interactions between local magnetic moments for both doped and undoped graphene. I will show that in both cases the interactions are primarily ferromagnetic for moments on the same sublattice, and antiferromagnetic for moments on opposite sublattices. This suggests that at sufficiently low temperatures dilute magnetic moments embedded in graphene can order into a state analogous to that of a dilute antiferromagnet. The results indicated that in the undoped case one expects no net magnetic moment. For doped graphene the moments at definite lattice sites interact over longer distances than those placed in interstitial sites of the lattice (1/R 2 vs. 1/R 3 ) because the former support a Kohn anomaly that is suppressed in the latter due to the absence of backscattering. In the last part of the presentation, I will discuss the electronic and magnetic properties of vacancies in intrinsic graphene. Using a mean field Hubbard model, I will describe the magnetic textures associated to removing a single atom (vacancy). Electronic and magnetic structure of graphene nanoribbons. This presentation covers some of the basic theoretical aspects of the electronic and magnetic structure of graphene nanoribbons, starting from the simplest tight-binding models to the more sophisticated ones where the electron-electron interactions are considered at the mean field approximation. Nanoribbons can be classified into two basic categories, armchair and zigzag, according to their edge termination, which determines profoundly their electronic structure Magnetism, as a result of the interactions, appears in perfect zigzag ribbons. 14

15 Microscopía Electrónica de nanostructuras: avances recientes Miguel J. Yacaman University Of Texas at San Antonio One UTSA Circle San Antonio, TX

16 Time-dependent transport in carbon-based materials Claudia Gomes da Rocha Technische Universitat Dresden, Alemania We focus on a theoretical studies of the effects of time-dependent fields on electronic transport through carbon-based devices. The physical response of such systems can be modified by an ac gating or a time varying bias and we highlight the main theoretical methods adopted to address transport phenomena with time dependence. Important technological applications in the area including quantum charge pumping and coherent destruction of tunneling are discussed taken into account the interplay between quantum interference and photon-assisted processes. 16

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19 Oxidation of metals Judit G. Lisoni 1 Depto. de Física, Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile, Santiago, Chile address corresponding author: jlisoni@ing.uchile.cl Oxidation of metals it is topic of general interest and of fundamental relevance in different fields. In particular, oxidation of metals is a concern in many applications, where materials and processing have to be finely adjusted in order to assure the successful fabrication of devices otherwise threatening the performance of it. Independent of the kind of applications it is of fundamental importance (and great fun too!) to understand the growth kinetic of metal oxides. In general, the oxidation of metals is a thermally activated process that can be separated in two regimes: low and high temperatures. The temperature at which these regimes can describe the oxidation kinetic varies from material to material. While the topic of metal oxidation in bulk systems is well understood [1-2], the oxidation behavior of low dimensionality systems -thin films and nanoparticles- is being intensively investigated since many new phenomena, different to what is observed in bulk systems, are observed. In this presentation I will first introduce the oxidation mechanisms known in bulk systems. Then, I will focus our discussion in the oxidation behavior of thin films. For that purpose, I will use as examples Ti(Al)N, Ni and W films. These materials have been selected because of their applications in non-volatile memory devices. [1] K. Hauffe, Oxidation of metals, Plenum Press, 1965; and references therein. [2] N. Birks and G.H. Meier, Introduction to high temperature oxidation of metals, Edward Arnorl (Publishers) Ltd, 1983; and references therein. 19

20 Spin excitations in metallic ultrathin films Antonio T. Costa 1, Roberto B. Muniz 1 and D. L. Mills 2 1 Instituto de Física, Universidade Federal Fluminense, Niterói, RJ, Brazil 2 Department of Physics and Astronomy, University of California, Irvine, CA 92617, USA antc@if.uff.br Spin excitations in metals are related to many important and fascinating phenomena such as spin relaxation, spin transfer torque and the generation of pure spin currents (a phenomenon also known as spin pumping). I will review various results [1] of our theoretical approach to the determination of spin excitation spectra in ultrathin metallic ferromagnetic films deposited on non-magnetic metallic substrates, and how our results compare to those of recent experiments. We calculate the dynamical transverse spin susceptibility using a realistic model to describe the electronic structure of the systems under consideration. The electrons responsible for magnetism in the ultrathin films are treated as itinerant and the metallic substrate is taken fully into account. Our approach works for spin excitations of any wavelength, from the center to the borders of the Brillouin zone. This means that we can obtain, using the same set of theoretical tools, the short wavelength spin waves probed via spin polarized electron energy loss spectroscopy (SPEELS), the spin exchange stiffness that comes out from Brillouin light scattering experiments, including the long wavelength excitations produced by neutron scattering, and the ferromagnetic resonance spectra. I will also show how our theoretical approach have been extended to include spinorbit coupling and how this affects our previous results. In particular I will show that the contribution of spin-orbit coupling to the finite lifetime of the ferromagnetic resonance mode in ultrathin films is of the same order as the spinpumping contribution. References [1] A. T. Costa, R. B. Muniz and D. L. Mills, Phys. Rev. B 68, (2003). [2] A. T. Costa, R. B. Muniz and D. L. Mills, Phys. Rev. B 69, (2004). [3] A. T. Costa, R. B. Muniz and D. L. Mills, Phys. Rev. B 70, (2004). [4] A. T. Costa, R. B. Muniz and D. L. Mills, Phys. Rev. B 73, (2006). [5] A. T. Costa, R. B. Muniz and D. L. Mills, Phys. Rev. B 74, (2006). [6] A. T. Costa, R. B. Muniz, R. Q. Wu, J. X. Cao and D. L. Mills, Phys. Rev. B 78, (2008). 20

21 Magnetization Reversal in Nanodots D. Altbir 1,5, N. Vargas 1,5, S. Allende 2,5, J. Escrig 1,5, B. Leigton 1,5, J. Mejía-López 3,5 and I.K. Schuller 4 1 Departamento de Física, Universidad de Santiago de Chile, USACH, Chile 2 Departamento de Física, FCFM, Universidad de Chile, Chile 3 Facultad de Fisica, P. Universidad Católica de Chile, Chile 4 Physics Department, University of California San Diego, USA 5 CEDENNA, Center for the Development of Nanoscience and Nanotechnology, USACH, Chile During the last years a great deal of attention has been focus on the study of regular arrays of magnetic particles produced by nanoimprint lithography. Besides the basic scientific interest in the magnetic properties of these systems, there is evidence that they might be used in the production of new magnetic devices, or as media for high density magnetic recording. In these nanostructures the properties they exhibit are strongly dependent on the geometry, and then a high control of the shape is fundamental for the correct understanding ad applications of such systems. In this presentation we focus on the study of the magnetization reversal in dots as a function of their geometry. By means of the Fast Monte Carlo Method, which will be explained in detail, we simulate the hysteresis for different dots and investigate the reversal modes that are responsible for the magnetization reversal. We also characterize the coercivity and remanence as a function of the asymmetry of the dot. From our simulations we obtained that the region of vortex nucleation and the chirality are totally controlled by the asymmetry and also we observed an interesting non-monotonic behaviour of the coercivity, which can be useful for applications. 21

22 Modificación de superficies por bombardeo de iones altamente cargados Marcos Flores Departamento de Física, Universidad de Chile, Av. Blanco 2008, Santiago, Chile La interacción de iones altamente cargados (highly charged ions, HCI) con superficies se ha transformado en un campo de mucho interés en los últimos años, en parte dado por la simplificación de los sistemas de obtención de los HCI y también por la posibilidades de aplicación de ellos en la modificación de superficies a la escala nanoscopica [1]. Cuando un HCI lento se aproxima a una superficie suceden una serie de fenómenos físicos son observados, como la formación de átomos huecos, en los cuales los electrones ocupan estados excitados, cascadas Auger, y emisión de partículas secundarias (electrones, iones, átomos, aglomerados y rayos X) [1-5], figura 1(a). En particular, un gran numero de electrones, son emitidos desde la superficie [1]. Se ha visto que los espectros de iones secundarios (SIMS) son altamente sensibles al estado de carga de los proyectiles [3]. El proceso de sputtering causado durante la interacción de los HCI con la superficie es conocido como sputtering potencial o sputtering electrónico en algunos casos. La respuesta dinámica de la red debido a los iones incidentes varia de acuerdo a la las características del material del blanco. Es conocido que la interacción HCI-superficie produce daño permanente en superficies aisladoras, óxidos metálicos y cristales iónicos, mientras que defectos en la red de sustratos metálicos solo han sido evidenciados en oro. Por ejemplo ver las imágenes de las figuras 1(b) y 1(c). Los modelos de explosión Coulombiana y mediante formación de defectos han surgido para explicar la formación de nanoestructuras en la superficie durante el bombardeo con HCI [4,5]. En esta presentación se dará una pequeña revisión de la utilización HCI para la modificación de superficies de distintos materiales reportados en la literatura. (b) (a) (c) Figura 1. (a) Representación de las distintas etapas durante la aproximación de un HCI a la superficie. (b) Nanopuntos formados por el impacto de Ar 9+ sobre una muestra de HOPG. (c) Nanocrater formado por el impacto de I 50+ sobre Si(111)7x7. Referencias [1] F. Aumayr, A. El-Said and W. Meissl, Nucl. Inst. and Meth. B 266 (2008) [2] The physics of the multiply and highly charged ions, edited by F. Currel, Klumer Academic Publishers, [3] T. Schenkel, A. Hamza, A. Barnes and D. Schneider, Prog. Surf. Sci. 61 (1999) 23. [4] J. Burgdorfer, C. Reinhol, L Hagg and F. Meyer, Aust. J. Phys. 49 (1996) 527. [5] F. Aumayr, and H. Winter, Phil. Trans. Roy. Soc. (London) 362, 77 (2004). 22

23 Conical carbon nanostructures E.Svasand Departamento de Física, Universidad Técnica Federico Santa María, Valparaíso , Chile. Carbon nanostructures have been a subject of extensive research since the synthesis of fullerenes [1] and carbon nanotubes [2]. In recent years, considerable efforts have been made to fabricate different carbon morphologies and explore their application. Carbon with a conical form exist in many different forms, as hollow fullerene cones[3], low angle conical carbon crystals[4], hollow nanocones[5], naturally occuring solid cones[6] and tubular cones[7] among others. Newer members of this family are nanohorns [8 10] and nanopipettes [11]. Perfect fullerene cones are found in industrial quantities in the so called Kvaerner Carbon Black & Hydrogen Process [12]. The cones represent perfect conical structures and consist of curved graphene sheets formed as hollow cones with a closed tip. Due to pure topological constraints there exist five discrete cone angles. If sectors of multiples of 60 are removed from a planar graphene sheet, and the free bonds are reconnected, conical structures are formed. Cones with 1 5 pentagons incorporated give cones with apex angles of 112,9 83,6, 38, and 19,2 respectively. m = 0 gives planar disks, or equivalently apex angle of 180 and m = 6 gives half spheres found at the end of closed nanotubes. The presence of non even circuits, like the pentagonal rings, promotes a non uniform distribution of charge. This makes cones more reactive than flat graphite and open ended nanotubes. AFM image of a fullerene cone This lecture will give an overview of the different conical carbon nanostructures, production methods, morphologies and possible applications with a more detailed presentation of the fulleren cones. References 1. Kroto HW, Heath JR, O Brien SC, Curl RF, Smalley RE. C60: Buckminsterfullerene. Nature 1985;318: Iijima S. Helical microtubes of graphitic carbon. Nature 1991;354(6348): K. Sattler and M. Ge. Observation of fullerene cones. Chemical physics letters, 220:192{196, S. Dimovski, J.A.Libera, and Y.Gogotsi. A novel class of carbon nanocones. Material Research Society Symp.Proc., 706, J.Liu, W.Lin, X.Chen, S.Zhang, F.Li, and Y.Qian. Fabrication of hollow carbon cones. Carbon, 42:667{691, J.A.Jaszczak, G.W.Robinson, S.Dimovski, and Y.Gogotsi. Naturally occurring graphite cones. Carbon, 41:2085{2092, Zhang GY, Jiang X, Wang EG. Tubulargraphitecones. Science 2003;300(5618): S. Iijima, T. Ichihashi, and Y. Ando, Nature 356, 776 (1992) 9. S. Iijima, M. Yudasaka, R. Yamada, S. Bandow, K. Suenaga, F. Kokai, and K. Takahashi, Chem. Phys. Lett. 309, 165 (1999). 10. S. Berber, Y. K. Kwon, and D. Tomanek, Phys. Rev. B 62, R2291 (2000). 11. R. C. Mani, X. Li, M. K. Sunkara, and K. Rajan, Nano Lett. 3, 671 (2003). 12. Kvaerner ASA. For production of micro domain particles by use of a plasma process. Patent No PCT/NO98/

24 A taste of photonics: plasmon polaritons in 1D heterostructures with left-handed materials L. E. O liveira Inst. de Física, Universidade Estadual de Campinas Unicamp, São Paulo, Brazil address: oliveira@ifi.unicamp.br In the last decade or so, the investigation of systems with negative indices of refraction [1] has greatly advanced due to intense theoretical and experimental work. That led to the realization of novel micro-structured materials exhibiting evidence of negative refraction. Recently, the fabrication of 3D optical metamaterials with both negative refraction and low absorption has given new impulse to attempts to obtain the socalled perfect lens [2]. The advent of those metamaterials has thus opened a new era for optical devices, and has also given considerable thrust to the area of plasmonics. Motivated by such developments, in the present work we derive the photonic band structure of a one-dimensional superlattice of alternate slabs of widths a and b composed of positive (n a >0) and negative (n b <0) refractive indices, the latter being dispersive, i.e., n b = n b ( ). Using Maxwell s equations and a transfer-matrix technique, we obtain the dispersion relation that describes the propagation of optical fields through the structure. For oblique incidence, the photonic dispersion indicates that the magnetic (electric) field in the frequency region around ε(ω) =0 and µ(ω) =0 leads to the propagation of magnetic (electric) plasmon polaritons in the case of TE (TM) modes. Furthermore, it is shown that if the plasma frequency is chosen within the photonic n(ω) =0 zero-th order bandgap [3], the coupling between light and plasmons weakens considerably. As light propagation is forbidden in that particular frequency region, the plasmon polariton essentially reduces to a pure plasmon mode [4]. frequency (GHz) (a) TE (b) TM ν m kd/π Figure 1. TE and TM dispersions in photonic periodic superlattices. Calculations were performed for air as slab A (ε = µ =1), and the Drude model for ε(ω) and µ(ω) in slab B (slabs with equal widths of 12 mm). Dotted lines indicate the pure electric/magnetic plasmon. Solid and dashed lines correspond to θ = π/12 and θ = 0 incidence angles, respectively. Refer ence s [1] V. G. Veselago, Sov. Phys. Usp. 10, 509 (1968). [2] J. Valentine et al, Nature 455, (2008). [3] J. Li, L. Zhou, C. T. Chan, and P. Sheng, Phys. Rev. Lett. 90, (2003). [4] E. Reyes-Gómez, D. Mogilevtsev, S. B. Cavalcanti, C. A. A. de Carvalho, and L. E. Oliveira, Europhys. Lett. 88, 24002/1-6 (2009) ν e 24

25 Estudio de la Dinámica de Nucleación y ensamble de Nanotubos de Carbono A. León 1, Z. Barticevic 2, M. Pacheco 2 1 Instituto deciencias Básicas, Facultad de Ingeniería, Universidad Diego Portales, Santiago, Chile 2 Depto. de Física, Universidad Técnica Federico Santa María, Casilla 110-V, Valparaíso, Chile alenjandro.leon@udp.cl Los nanotubos de carbono son sistemas cuasiunidimensionales con propiedades electrónicas, mecánicas y químicas que motivan su estudio para potenciales aplicaciones tecnológicas en muchas áreas [1]. En la actualidad se dispone de métodos de síntesis y purificación de nanotubos de carbono a gran escala [2], pero hoy todavía no se tiene un método para satisfacer la demanda de nanotubos con igual topología y sin defectos. Existe un criterio aceptado respecto de que el método de crecimiento impulsado por partículas catalizadoras sería el más apropiado para sintetizar nanotubos de carbono de pared simple [3]. Por esta razón, se han realizado un gran número de estudios teóricos que han tratado de dar luces para entender el mecanismo de crecimiento de nanotubos a partir de partículas metálicas. Los modelos basados en dinámica molecular clásica (MD) y que usan potenciales fenomenológicos han estudiado la dinámica de crecimiento en diferentes condiciones e incluyendo el sustrato que soporta la partícula [4]. Los resultados aportados por estos estudios han permitido avanzar sustancialmente en el conocimiento de la dinámica de crecimiento de nanotubos. En particular el trabajo de Ding y colaboradores [4] muestra que la partícula metálica pasa por una etapa en que los átomos de carbón difunden saturando a la patícula antes de comenzar el proceso de nucleación. Recientemente se han publicado algunos trabajos usando dinámica molecular cuántica (DFTB/MD) [5] cuyos resultados indicarían que no es necesario tener la partícula catalizadora saturada de carbón para que se inicie la nucleación, contrario a los resultados obtenidos por Ding y colaboradores con la dinámica molecular clásica MD. En este trabajo se realiza un estudio teórico de la primera fase de la nucleación de nanotubos de carbono individuales a partir de una partícula catalizadora de Fe. Se utiliza un modelo basado en un autómata celular (CA) [6] en diferentes condiciones de temperatura, tamaño de la nanopartícula catalizadora y afinidad con el sustrato que soporta a la partícula. Además consideramos distintos estados de saturación de la partícula durante la primera parte del proceso de nucleación. Figura 1. Simulación del proceso de nucleación de un nanotubo de carbono a través de una partícula de Fe 40. Referencias [1] Dresselhaus, et al, P. Carbon Nanotube: Synthesis, Structure, Properties, and Applications; Springer: New Yord, [2] A. Thess, et al, Science 273 (1996) 483. [3] S. Irle, et al, Nano Res. 2 (2009) [4] F. Ding, K. et al, Phys. Chem B 108 (2004) [6] "New Constructions in Cellular Automata", Edited by D. Griffeath and C. Moore, Oxford, University Press (2003). 25

26 Modelización de la interacción Coulombiana en nanoestructuras C. González-Santander 1 y F. Domínguez-Adame 1 1 Depto. de Física de Materiales, Universidad Complutense de Madrid, Av. Complutense 28040, Madrid, España cglezsantander@fis.ucm.es En los últimos años se han investigado ampliamente los efectos de la reducción de la dimensionalidad en nanoestructuras. Algunos fenómenos que a escala macroscópica son bien conocidos, resultan difíciles de estudiar en sistemas de baja dimensionalidad por el papel relevante que juega el potencial de confinamiento. La ecuación de Schrödinger no suele presentar soluciones analíticas en estos problemas, por lo que frecuentemente se acude a soluciones obtenidas por métodos variacionales. En esta contribución se va a exponer un método alternativo y muy robusto, basado en el potencial no local (NLP, de la acepción inglesa non-local potential) separable, en el cual el potencial Coulombiano se reemplaza por un operador proyectivo [1-3]. Esta sustitución conduce a una ecuación resoluble exactamente de manera que los estados electrónicos del sistema pueden obtenerse con un esfuerzo computacional modesto. Lo más importante y destacado de este método es que siempre es posible encontrar un NLP que reproduzca los estados electrónicos originales de un sistema cuántico dado, por lo que realmente no existe límite teórico a la precisión con la que se pueden calcular los estados del sistema. La dificultad radica en que el NLP correcto se desconoce a priori. Sin embargo, sea cual sea el NLP empleado, es posible expresar la solución general de manera cerrada y compacta. La estrategia entonces es probar diferentes NLPs hasta lograr un buen acuerdo con los resultados experimentales. En este sentido, este método se ha empleado satisfactoriamente para estudiar puntos cuánticos y obtener la energía de ligadura de excitones [4] y de impurezas hidrogenoides [5]. Recientemente, esta técnica ha sido extendida a sistemas unidimensionales [6]. Como ejemplo, en la Fig. 1 se puede observar la evolución de la energía de ligadura con el tamaño para un hilo cuántico de In 0.06 Ga 0.94 N. Figura 1: Energía de ligadura en función del tamaño lateral del hilo para excitones de huecos pesados y ligeros (líneas continuas superior e inferior, respectivamente). La energía de ligadura de los excitones libres (E B =Ry*) está indicada con líneas discontinuas. Por comparación se presenta en línea de puntos los valores obtenidos con un cálculo perturbativo. Referencias [1] B. W. Knight y G. A. Peterson, Phys. Rev. 132, 1085 (1963). [2] P. R. Sievert y M. L. Glasser, Phys. Rev. B 7, 1265 (1973). [3] M. L. Glasser, Surf. Sci. 64, 141 (1977). [4] S. López y F. Domínguez-Adame, Semicond. Sci. Technol. 17, 227 (2002). [5] R. P. A. Lima, M. Amado y F. Domínguez- Adame, Nanotechnology 19, (2008). [6] C. González-Santander y F. Domínguez- Adame, Physica E 41, 1645 (2009). 26

27 Transporte electrónico en sistemas compuestos por nanocintas de grafeno Luis Rosales A. 1 1 Instituto de Física, Pontificia Universidad Católica de Valparaíso, Casilla postal 4059, Valparaíso, Chile luis.rosales@ucv.cl Desde el primer reporte experimental de una capa de grafeno estable puesto sobre un sustrato de Óxido de Silicio, realizado por el grupo de Manchester en el año 2004 [1], esta estructura cristalina ha atraído mucho interés de la comunidad científica. Sus especiales y novedosas propiedades electrónicas, la estabilidad mecánica a temperatura ambiente, junto con la posibilidad de obtener heteroestructuras diseñadas a través de litografía electrónica de alta resolución, sugieren que estos sistemas tienen una gran potencialidad en el uso de nuevas aplicaciones en nanociencia y nanotecnología. En el caso particular de nanocintas de grafeno, las propiedades electrónicas y de transporte están definidas por el confinamiento cuasi-unidimensional, como también, por la forma que adoptan los átomos de carbón en los bordes de estas cintas. En este sentido, se pueden encontrar dos casos de máxima simetrías: nanocintas zigzag (ZGNRs) y nanocintas armchair (AGNRs). Estos sistemas nanométricos han sido ampliamente estudiados en los últimos años, lográndose determinar el comportamiento general de las propiedades física que éstos poseen [2]. Independientemente del gran avance que se ha logrado en el entendimiento de estos sistemas, aún quedan muchas preguntas abiertas, las cuales deben ser estudiadas en detalle, como por ejemplo, las posibles modificaciones de las propiedades de transporte electrónico debido a defectos topológicos o el estudio de las propiedades electrónicas de heteroestructuras formadas por cintas de distintos tipos. En esta charla se mostrarán estudios teóricos de las propiedades electrónicas y de transporte de sistemas basados en nanocintas armchair. Se mostrarán dos tipos de sistemas: i) una superred de defectos topológicos tipo antidots, ii) una doble juntura de cintas de grafeno de distintos anchos, puestas en una configuración crossbar simétrica. En ambos casos se mostrará cuales son las posibles modificaciones de las propiedades electrónicas y de transporte, colocando especial énfasis en las modulaciones de la conductancia y en las curvas de corrientes características de estos sistemas nanométricos [3 y 4]. Referencias [1] K. S. Novoselov, A. K. Geim, S. V. Morozov, D. Jiang, Y.Zhang, S. V. Dubonos, I. V. Grigorieva, and A. A. Firsov, Science, 306, 666 (2004). [2] A. H. Castro Neto, F. Guinea, N. M. R. Peres, K. S. Novoselov, and A. K. Geim, Rev. Mod. Phys. 81, 109 (2009) [3] L. Rosales, M. Pacheco, Z. Barticevic, A. León, A. Latgé, and P. A. Orellana, Physical Review B 80, , (2009) [4] J. W. Gonzalez, L. Rosales y M. Pacheco, Physica B: Condensed Matter 404, 2773,

28 Structure and Composition of Ultrathin Films Torgny Gustafsson 1 1 Department of Physics and Astronomy, Rutgers University, Piscataway, NJ 08854, USA gustaf@physics.rutgers.edu The properties of ultrathin films and especially their interfaces are central in a wide range of fields. This has become especially important as the size of many practical devices is decreasing and therefore surfaces and interfaces constitute an ever larger fraction of the total device. Our group has concentrated on the study of the structure and composition of films, interfaces and surfaces of model systems and materials which are of importance for microelectronic devices. The techniques we are using include Medium Energy Ion Scattering (MEIS) [1], a low energy, high resolution version of conventional Rutherford Backscattering Spectroscopy (RBS), complemented by X-ray Photoelectron Spectroscopy (XPS) for studying the electronic structure, Scanning Probe Microscopy (SPM) to get information about the local topology and electrical measurements to get information related to device performance. The central material in microelectronics has of course been silicon. I will therefore first discuss the Si/SiO 2 interface, mainly to give a historical perspective. SiO 2 has traditionally been used as an insulator in high performance devices, but as device sizes decrease, it is now being replaced by materials with higher dielectric constants ( high-k ), such as HfO 2 and ZrO 2. I will discuss properties such as interdiffusion and thermal stability of such films. Finally, I will discuss novel channel materials, i.e. materials with higher electrical performance than Si, for example GaAs, Ge and InGaAs and their interaction with high-k films [2]. References [1] T. Gustafsson, in Ion Beams in Nanoscience and Technology (Hellborg, Ragnar; Whitlow, Harry J.; Zhang, Yanwen (Eds.)), Springer, Berlin (2010). [2] H. D. Lee et al, Appl. Phys. Lett. 94, (2009) 28

29 Structure and magnetic properties of ultrathin Ni films grown on Pd (100) C. Parra 1, P. Häberle 1, P. Gastelois 2, M. D. Martins 2, W. A. A. Macedo 2 1 Depto. de Física, Universidad Técnica Federico Santa María, Casilla 110-V, Valparaíso, Chile 2Laboratório de Física aplicada, Centro de Desenvolvimiento da Tecnologia Nuclear, CP 941, Belo Horizonte, MG, Brazil address corresponding author: carolina.parra@usm.cl Through the deposition of ultrathin films is possible to stabilize the structure of certain materials, which then display interesting and striking properties that deviate substantially from those shown by the bulk. By varying the surface features induced by heteroepitaxial growth, as roughness, strain and intermixing between film and substrate, one can modify the structural properties in order to improve the magnetic properties of the film (spin reorientation and magnetic moment). In order to investigate more systematically the influence of the lattice strain induced by the substrate on the structure and, as a consequence, on the magnetism of the epitaxial Ni films, we have characterized the growth of ultrathin Ni films on Pd(100). The Pd fcc substrate has been chosen in order to favor a contraction of the Ni films in the vertical direction (tetragonal distortion fct) due to an increased intralayer strain caused by pseudomorphic growth. Thus according to the fact that the bulk lattice mismatch between fcc Ni and fcc Pd is 9.5% Scanning tunneling microscopy (STM), reflection high energy electron diffraction (RHEED) and Auger electron spectroscopy (AES) have been used to investigate morphology, composition and structure of the ultrathin Ni films at RT. The magnetic properties were described in-situ by magnetooptic Kerr effect (MOKE) in the longitudinal geometry. Our study demonstrates that three thickness regimes can be distinguished: Up to 6.5 ML films growth pseudomorphically displaying a face-centered tetragonal structure (fct), in agreement with the linear elasticity theory prediction. No longitudinal Kerr signal is detected in this thickness range. Figure 1. Morphology, structure and coercive field measured on Ni thin films grown on Pd(100) at RT as a function of coverage. From 6.5 ML to 10.5 ML an onset of a new interlayer distance of around 1Å, which is maintained along the growth of the further four layers, occurs simultaneously with the appearance of filament-like structures. This is presumably connected to the relief mechanism of the strained fct films, according to the RHEED measurements which show the most drastic relaxation of the lateral lattice parameter in this thickness range. Our RT MOKE measurements show an onset for the in-plane magnetization at 6.5ML. In this range the coercive field is not significantly dependent on thickness. Finally above 10.5ML the films recover their face centered cubic-fcc parameters and the surface morphology evolves to a net-like structure that connects the whole surface. The hysteresis loop at this coverage shows an enhancement of the coercivity and a decrease of Kerr intensity. 29

30 Moléculas biológicas para aplicaciones nanotecnológicas V. del Campo 1, I. Vergara 2, U. Volkmann 2 1 Depto. de Física, Universidad Técnica Federico Santa María, Av. España 1680, Valparaíso, Chile 2 Facultad de Física, Pontificia Universidad Católica de Chile, Av. Vicuña Mackenna 4860, Santiago, Chile valeria.delcampo@usm.cl La naturaleza ya ha encontrado solución a muchas de las preguntas que nos hacemos y a los problemas con que nos encontramos. Así es que, la bionanotecnología busca utilizar moléculas biológicas para aplicaciones nanotecnológicas. Para estudiar la naturaleza, partimos desde las cosas simples para avanzar a las más complejas. En este caso, para estudiar moléculas biológicas comenzamos por estudiar alcanos. Estos hidrocarburos son parte de la estructura básica de moléculas complejas como lípidos y triglicéridos. En este trabajo, estudiamos películas delgadas de alcanos, su estructura y transiciones en temperatura. Con Difracción de Rayos X (XRD), analizamos la estructura cristalina de las películas. Con Reflexión de Rayos X (XRR), estudiamos la estructura de capas de las películas delgadas y las transiciones de estas estructuras en temperatura. Con Microscopía de Fuerza Atómica (AFM), conocemos la topografía de la película y como cambia al calentar la muestra. Con Elipsometría, analizamos las propiedades ópticas de la muestra, como espesor, índice de refracción, y polarizabilidad de las moléculas. Los resultados obtenidos nos muestran que sobre un substrato de silicio se depositan dos capas con los alcanos acostados y luego una capa con las moléculas orientadas perpendiculares al substrato. La capa perpendicular tiene una estructura ortorrómbica que se desordena al calentar la película. Al aumentar aún más la temperatura las moléculas de la capa perpendicular forman gotas sobre las capas paralelas, que a su vez sufren una transición de fase, posiblemente a fase líquida. Al enfriar, no se recupera la estructura inicial, si no que se forman estructuras ortorrómbicas de varias capas perpendiculares [1-3]. Figura 1. Transición de fase en temperatura de una membrana celular. Esta transición ocurre lentamente entre los 40 C y los 50 C Con el estudio de alcanos como primer paso, avanzamos al análisis de moléculas biológicas, en particular, membranas bilipídicas. Éstas son membranas celulares que separan la vida dentro de la célula del medio en que vive, permitiendo el paso de agua y otros nutrientes. El estudio de estas membranas tiene aplicaciones nanotecnológicas como biosensores y suministro de medicamentos. Agradecimientos a FONDECYT No , y a U. S. NSF No. DMR Referencias [1] M. Bai, K. Knorr, M. J. Simpson, S. Trogisch, H. Taub, S. N. Ehrlich, H. Mo, U. G. Volkmann and F. Y. Hansen; Europhys. Lett. 79, (2007). [2] E. A. Cisternas, T. P. Corrales, V. del Campo, P. A. Soza, U. G. Volkmann, M. Bai, H. Taub, and F. Y. Hansen; J. Chem. Phys, 131, (2009). [3] V. del Campo, E. Cisternas, H. Taub, I. Vergara, T. Corrales, P. Soza, U. G. Volkmann, M. Bai, S.-K. Wang, F. Y. Hansen, H. Mo and S. Ehrlich; Langmuir, 25 (22), (2009). 30

31 Poster SNS Nanostructured Junctions Fabrication for Astronomical Devices...33 Propiedades eléctricas de películas formadas por nanopartículas de oro...34 Unspected Red- to Near-IR-Emiting CdS- Carbonaceous-Hetero Capped Dots...35 Nanopartículas de Níquel y Cobalto Obtenidas Mediante Pulverización Catódica en Vacío...36 Propiedades electrónicas de baja energía en nanocintas de grafeno armchair corrugadas...37 Propiedades bactericidas de matrices poliméricas híbridas modificadas con nanopartículas y complejos de plata...38 El efecto de la lipofilia sobre la respuesta solvatocrómica de betainas de fenolato en micelas...39 Diseño de un filtro de spin eficiente con una molécula de triple punto cuántico en un interferómetro de Aharonov-Bohm con interacción spin-órbita RSO...40 Estudio estructural del proceso de captura de drogas dependiente de ph del dendrímero PAMAM G Transport properties of a Kondo dot with side attached non interacting Aharonov-Bohm quantum-ring...42 Nanopartículas de plata como potenciales sensibilizadores en celdas fotoelectroquímicas regenerativas...43 Fluorescencia de meso-tetrafenilporfirina amplificada por superficie metálica de plata...44 Nano-composites based in nanotube of TiO2 with Ruthenium complex for the study of reduction of CO Estudio de Propiedades Biocidas en Nanocompósitos de Polipropileno con Nanopartículas de Cobre...46 Fe-Porphyrin Attached on Single-Wall Carbon Nanotubes for Heterogeneous Catalysis in Oxygen Reduction Reaction...47 Pérdida de energía de protones en nanotubos de carbono...48 Transporte controlado de un fotón a través de un arreglo 1-D de cavidades acopladas en interacción con átomos del tipo V...49 Resistivity of thin metallic films induced by electron-rough surface scattering and electron-grain boundary scattering