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Séminaire de l’équipe « Oxydes en basses dimensions » de l’INSP

Revealing the Color and Shape of Nanostructures : How STM Studies May Offer New Insights on Nanomaterials Properties ? - Fernando Stavale - Mardi 8 décembre 2015 à 10 h 30

INSP - 4 place Jussieu - 75252 PARIS Cedex 05 - Barre 22-32 - 4e étage, salle 407

Fernando Stavale - Brazilian Center for Physics Research, Rio de Janeiro

Abstract

Progress in science has been always made through continuous development of innovative techniques either as ground-breaking as the discovery of X-ray diffraction or brainstorming as the invention of the scanning tunneling microscope (STM). This latter has been in recent decades further improved and became the technique of choice for characterization of great number of materials systems, including biomaterials, nanocomposites and nanoparticles. Scanning probe microscopes (SPMs) are able to measure the variation of the electric or magnetic forces between the probe and the surface, or even move individual atoms and molecules to form artificial arrangements. Their ability to access real space information of surfaces with atomic resolution has changed our perception about materials characterization and opened plenty of room at the bottom. Although SPMs are capable to image surfaces with sub-nanometric resolution, their inherent chemical insensitivity is certainly an important technique drawback. To overcome this disadvantage the photon-STM has been proposed and developed years ago. In a photon-STM, a photon detector is placed near to the tip-sample region and the light emission response of nanometer-sized regions under the tip apex is measured. The photon-STM has been in several investigations used to obtain simultaneously structural, morphological and chemical information of surfaces and nanostructures and opened new possibilities for material characterization. In this contribution, we briefly discuss some of our studies on STM and STM induced-light emission characterization of metal-oxide systems, such as (a) chromium doped MgO films ; (b) europium-oxides nanoclusters ; (c) lithium-molybdate nanostructures ; and (d) intrinsic-defects in ZnO films. These oxide systems are of great importance in heterogeneous catalysis, optical-electronic devices and photovoltaics, and the use of local cathodoluminescence spectroscopy offer a new tool to investigate them properties at the nanoscale.