ICMCTF2007 Session F1-1: Advanced Characterization / General Topics

Monday, April 23, 2007 10:00 AM in Room Sunset

Monday Morning

Start	Invited?	Item
10:00 AM	Invited	F1-1-1 Interpretation of Reflection Electron Energy Spectra: From the Dielectric Description to Hydrogen Quantification at Surfaces F. Yubero (ICMSE (CSIC-Univ. Sevilla), Spain) The interaction of swift electrons (kinetic energies in the 200-2000 eV range) with surfaces in reflection electron experiments can be linked to valuable information about the surface properties of materials as their electronic structure, dielectric response, electron inelastic mean free paths, and more recently, the Hydrogen quantification at the surface of polymers and other carbon based materials. In this contribution we will focus on the progress of our research group on the understanding of the technique to extract two very different kind of information. On the one hand, the dielectric response of a surface in the 3-100 eV energy range from the appropriate description of electron energy losses due to plasmon and other intra and interband electron excitations [1]. On the other hand the hydrogen content at the surface in diamond-like carbon and polymeric thin film materials by the quantification of the intensity of the elastic peak stemming from the backscattering of electrons with the hydrogen atoms present at the surface of the samples [2]. We will illustrate practical applications of both strategies of analysis. [1] F.Yubero et al., Phys. Rev. B 53 (1996) 9719. S.Tougaard et al., Surf. Interface Anal. 36 (2004) 824. [2] F.Yubero et al., Appl. Phys. Lett. 87 (2005) 084101. V.J.Rico et al., Diamond Relat. Mater. In press (available online 2006).
10:40 AM		F1-1-3 Characterization of Crystalline Nanostructures by Electron Energy Loss Spectroscopy H.J. Steffen (Hochschule Mannheim, Germany) Different crystalline structures of nanosized metallic particles with spherical and cylindrical geometry were investigated by the calculation of energy loss functions. The modes of collective electron density oscillations were derived by solving the stationary wave equation that is based on a combined hydrodynamic and density functional theory. The results reveal the influence of particle size, geometry and lattice parameter on the energy position of the low energy loss peaks.
11:00 AM		F1-1-4 Characterization of Organic Monolayers on the Surface of Aluminum in the Process of Thermal Treatment N. Hirani (Interm Student, NGTC, Novelis Inc., Canada); D. Chvedov (Surface Scientist/Project Leader, Canada); J. Hunter (Technical Leader, , NGTC, Novelis Inc., Canada) Comprehensive characterization of organic monolayers on the surface of rolled metal sheet is an extremely difficult task due to film thickness, alteration of the nascent film by high vacuum associated with a number of surface analytical techniques and surface topography of the aluminum substrate. The present study explore various modes of the FTIR analysis including Surface Enhanced Infrared Spectroscopy (SEIRA) to characterize the monolayer of the residual lubricant oil left on the surface of aluminum sheet after the rolling process. Conventional approaches of preparation of flat samples for SEIRA analysis are based on the gold plating process and alter the nascent organic film. Thus, deposition of gold nano-particles from aqueous suspensions has been used to create plasmons on the surface enhancing IR signal. The hydrocarbon peaks were enhancement by a factor of 3 indicating that not all mechanisms of enhancement have been engaged. Organic films after thermal treatment did not demonstrate any enchantment of IR signal, likely due to structural constrains imposed by the thermal treatment on the films and therefore restriction on the mutual orientation of the plasmons and molecules embedded in the film. Only IR signals associated with organic film were enhanced. The IR signal related to the underlying aluminum oxide film was not enhanced. Variations in the angle of incident in Mutiple variable ATR mode of IR Spectroscopy allowed for accentuation of various parts of the IR spectrum. The FTIR work was supported by measuring absolute surface carbon content using direct combustion method (LECO) and wettability by water. As expected the thermal degradation of the residual rolling oil caused decrease in carbon content of the film and increase in the wettability of surface. However, it was also found that there is a direct proportionality between the cosine of contact angle of water and an absolute amount of carbon on the surface in the process of thermal treatment.
11:20 AM		F1-1-5 FTIR Spectroscopy: IRRAS and Microspectroscopy, a Tool to Investigate Thermally Grown Oxide Scales B. Lefez (Lastsm Upres-Ea 1290, France); J. Lopitaux, B. Hannoyer (Universite de Rouen, France); M.P. Bacos (Office National d'Etudes et de Recherches Aerospatiales (ONERA), France) The main goal of this work is to show complementary of employing reflectance infrared spectroscopy to determine the composition of oxide films on metal surfaces. Illustration is reported on oxidation of alpha2- TiAl (Ti75-Al25) and gamma-TiAl (Ti50-Al50) alloys, carried out at 650°C in air atmosphere. Reflectance infrared spectra were recorded on a FTIR 710 Nicolet spectrophotometer, equipped a Nicolet IR plan microscope. The knowledge of the infrared optical constants allows to predict the infrared reflection spectra of different thin layers. To illustrate these computations the first band observed for a thin film (200 nm) of Al₂O₃ is the higher longitudinal optical (LO) mode, the position of which is 920 cm^-1 for alpha- Al₂O₃, 930 cm^-1 for gamma- Al₂O₃ or a broad band at 980 cm^-1 for amorphous Al₂O₃. In the case of TiO₂/alloy system, the LO mode moves from 830 cm^-1 for rutile TiO₂ to 880 cm^-1 for anatase TiO₂.@A peak fit program was applied to the spectra in order to extract each oxide contribution. The position of the fitted single absorption bands allows to identify the different oxides. The oxide grown on a-TiAl phase, consists of a-Al₂O₃ and rutile TiO₂ (24h to 500h of heat treatment), gamma-Al₂O₃ and rutile TiO₂ for 1000h of heat treatment. Chemical maps reveal heterogeneous distribution of the oxides in the layer. A detailed surface characterization showed that the surface was covered with a continuous alpha-Al₂O₃ layer and locally with a Al₂O₃/TiO₂ mixture. In the case of gamma-TiAl oxidation, the oxide film consists of alpha-Al₂O₃, gamma-Al₂O₃ and rutile TiO₂ mixture. FTIR spectroscopy provides important information about amorphous, poor or well crystallized materials when X ray diffraction is only convenient for crystallized phases. The advantages of this technique are that it is non destructive, requires no low vacuum and no sample preparation, whereas a conductive layer deposition is necessary to observe the oxides by SEM.