Advanced Structural and Chemical Characterization of Complex Materials at the Nanoscale: The cases of Misfit Nanotubes and Amorphous Carbon Thin Films - Luc Lajaunie

Luc Lajaunie - Laboratorio de Microscopías Avanzadas, Instituto de Nanociencia de Aragón, Universidad de Zaragoza, 50018 Zaragoza, Spain

Lundi 20 novembre 2017 à 10 h 30

IMPMC - UPMC - 4 place Jussieu, 75005 Paris, tour 23, 4e étage, couloir 22-23, salle 401

Abstract

Thanks to recent developments in transmission electron microscopy (correctors, monochromators, detectors…), it is now possible to acquire simultaneously structural and chemical data with sub-angström resolution. However beyond “colour maps” and ideal case scenarios, obtaining quantitative chemical information from electron-beam sensitive and structurally complex materials is still challenging. In this contribution, we will show how to extract a wealth of structural and chemical information from such complex materials.

The first part of this contribution will be dedicated to misfit nanotubes (NTs). Misfit layered compounds are intergrown materials with a general formula [(MX)_1+x]_m[TX₂]_n (M is rare earths, Pb, Sb, etc; T is Ti, V, Cr, Nb, etc. and X is S, Se) [1]. In 2011, NTs based on misfit compounds were synthetized for the first time and the syntheses were generalized later to other chalcogenide systems. Here, we report, for the first time, the synthesis of oxide-based misfit NTs [2-3]. A combination of high-resolution STEM-HAADF imaging (including image simulations), spatially-resolved EELS, and density functional theory calculations are used to discover the formation of new phases within these NTs. This new phases significantly differs from the bulk starting materials, inducing different electronic properties. Comparison with chalcogenide-based misfit NTs will also be provided [4-5].

The second part of this talk will be dedicated to hydrogenated amorphous carbon thin films which are already used by the industry in numerous applications. To improve their performances, a full understanding of their local chemistry is highly required. In this contribution, we will develop new procedures to extract properly and reliably quantitative chemical information from EELS spectra. In addition, the coupling of multi-wavelength Raman and EELS spectroscopies will be discussed. Our results provide a complete combination of C-hybridization, spatial elemental analyses and structural defects studies for shedding light on these complex materials [6].

Calcium cobalt oxide misfit nanotube

[1]. J Rouxel, A Meerschaut, GA Wiegers, J. Alloy Compd. 229 (1), 144-157 (1995)

[2]. LS Panchakarla, L Lajaunie, A Ramasubramaniam, R Arenal, R Tenne, ACS Nano 10 (6), 6248–6256 (2016)

[3]. LS Panchakarla, L Lajaunie, A Ramasubramaniam, R Arenal, R Tenne, Chem. Mater. 28 (24), 9150–9157 (2016)

[4]. LS Panchakarla, L Lajaunie, R Tenne, R Arenal. J. Phys. Chem. C 120 (29), 15600–15607 (2016)

[5]. L Lajaunie, G Radovsky, R Tenne, R Arenal. Submitted

[6]. L Lajaunie, C Pardanaud, C Martin, P Puech, C Hu, MJ Biggs, R Arenal, Carbon 112, 149-161 (2017)