Group Seminar

The department's seminar takes place on Tuesdays, 1:30 pm, room F207 (Collegezaal G). It may concern ongoing research or manuscript discussion.

regular schedule 2008


 January 8

Meng-Yue Wu

 

 January 15

Mark Freese

 

 January 22

Vikas Kumar

 

 January 29

Alexandro Grabulov

 

 February 12

Jouk Jansen

 

 February 19

Ugo Lafont

 

 March 11

Stephan Janbroers

 March 18

Mauro Porcu



MSc graduation talk: June 6 (Friday), 2008, 10 am, room F206


In-Situ Transmission Electron Microscopy of Electrodeposition
Technical Development and Beam Effects
Mark den Heijer

abstract

We have performed in-situ real-time transmission electron microscopy of deposition and stripping of copper on gold from a sulfidic acid solution with additives, in order to evaluate this technique for unravelling the working mechanism of the additives. The additives that we have investigated are Poly(ethylene glycol) (PEG), Mercapto-propanesulfonic acid sodium salt (MPS), chloride, and bromide, the combination of which makes up a model system that exhibits the superfilling effect essential to microchip manufacturing.

We use a completely sealed three electrode electrochemical TEM cell with electron transparent windows to conceal the liquid. This cell allows TEM observations, in particular in the form of movies, of the processes at the solid-liquid interface with a spatial resolution of 10 nm at a frame rate of 30 Hz. We have implemented several small improvements to the original design and propose a second generation design.

Using the improved cells we have observed deposition and stripping for all the additive solutions. The additives have a clearly observable effect on the morphology of the initial stages of deposition. We have also shown that it is possible to directly observe variations in the copper ion concentration in the liquid with the TEM.

Contrary to earlier work without additives, our observations have revealed obvious electron beam effects in all solutions. We have observed a beam effect in the liquid and on the liquid/window interface in solutions containing PEG and/or MPS. And we have observed a beam effect on the deposition of copper from chloride solution. The copper cluster density in the beam illuminated area is found to be an order of magnitude higher compared to that outside the illuminated areas. This finding impairs the application of the in-situ TEM technique for the study of the functioning of the additives, because the real time observations, which are necessarily on irradiated area, are not representative for what happens outside of an electron microscope. The development and use of low dose techniques that we have suggested may alleviate the beam effects to such an extent that undisturbed in-situ TEM studies of electrochemical deposition in the presence of additives becomes feasible.

Using the beam effect, by selectively depositing several lines, we have demonstrated electron beam induced deposition in the liquid, which may be developed into a lithography technique. 

 

appliant post-doc: May 9 (Friday), 2008, 10 am, room E005


Development and Testing of (M)EAM Potentials for Elements and Alloys
Jelinek Bohumir, Center for Advanced Vehicular System, Mississippi State University

abstract

To produce an alloy with desired properties, it is important to understand the effects of alloying elements and the phenomena involved in the alloy production process. Computational modeling and simulation provide cost effective methods of exploring interactions between individual alloying elements and studying the phenomena in alloy production.
An accurate modeling of the structure and properties of an atomic system can be performed by first-principle methods, possibly involving calculation of spatial electron density in the simulated system.
However, first-principle simulations of the phenomena of interest may require a number of atoms that exceeds the available computational resources.
An alternative to first-principle methods is to use semi-empirical nteratomic potentials. The effective evaluation of such potentials can allow modeling of systems with more than a million atoms. This presentation will introduce the work on the construction and testing of interatomic potentials for metallic alloys done at the Center for Advanced Vehicular System, Mississippi State University.

 

guest talk: May 15 (Thursday), 2008, 10 am


Interpretation of fine structure in electron energy-loss spectroscopy (EELS)
R.F. Egerton, University of Alberta and National Institute for Nanotechnology, Edmonton, Canada

abstract

We have performed FEFF calculations to find out what factors determine the delocalization of the information obtainable from analysis of the fine structure of an ionization edge in EELS. Both inelastic and elastic scattering of the emitted wave appear to be important. One conclusion is that, especially at high energy loss, one can expect worse spatial resolution in a chemical map (showing bonding changes, for example) compared to an elemental map of the same area of the specimen.
We have also investigated Fourier-ratio deconvolution as a technique for separating the spectral components recorded from an inhomogeneous (e.g.multilayer) specimen. This technique appears to have several advantages over the subtraction of spectral intensities.

 

master project: April 25 (Friday), 2008, 11 am, room F205


In-situ Transmission Electron Microscopy of Electrochemical Deposition: Technical Development, Beam Effects and Lithography
Mark den Heijer

 

 

Naam auteur: Ulrike
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