2016 Materials science lecture series: advanced materials - 22 November 2016
Nov 22, 2016 - 10.50 uur
Expertisecentrum voor Digitale Media
Lokaal Auditorium EDM
de heer Rajesh RAMANETI
MRS/E-MRS joint student chapter, Hasselt University with IMO-IMOMEC: 2016 materials science lecture series: advanced materials.
Speaker: Dr. Claudia Fleischmann, Senior researcher, IMEC, KU Leuven.
Topic: 3D atom-by-atom material analysis: Fundamentals, applications and challenges in atom probe tomography
Chaired by: Prof. Dr. Frank Renner, IMO-IMOMEC, Hasselt University
Tuesday 22 November 2016, 10:50 -12:00
EDM auditorium, Wetenschapspark 2, Hasselt University, Campus Diepenbeek.
Contemporary innovation in various fields of applications (nano-electronics, energy materials, structural steels, etc.) originate primarily from obtaining understanding and control of the material properties at the (sub) nanometric level, allowing for size reduction, introduction of functional interfaces or 3dimensional nanostructures, incorporation of additives at specific (lattice) sites, etc. Key to this is the ability to acquire full quantitative compositional and 3D data with a sub-nanometric spatial resolution and high sensitivity. Therefore, metrology has nowadays evolved towards addressing material properties at the atomic level, be it without spatial resolution (i.e. nuclear probes, emission channeling, synchrotron based techniques, etc.) or with atomic-scale spatial resolution (i.e. 3D transmission electron microscopy (TEM) tomography or atom probe tomography - APT).
In this respect, atom probe tomography has become a very powerful concept as it provides a full 3D quantitative compositional analysis of materials with an excellent sensitivity (10 ppm) and a near-atomic spatial resolution (δlateral ~ 23 Å, δdepth ~ 0.5 Å). The APT technique exploits the concept of atom-by-atom field evaporation of individual atoms from the surface of a needle-shaped sample (~100 nm tip radius) and their quasi-stereographic projection (with 106 x magnification) onto a 2D position-sensitive detector. Offering the unique possibility of unraveling the 3-dimensional structure of complex advanced materials at the atomic level, APT plays a key role in understanding atomic scale processes such as atomic redistribution, segregation, diffusion, precipitate or cluster formation etc. in these material systems.
This lecture will introduce the basic concepts of atom probe tomography, including field evaporation, ion detection and data reconstruction, and will briefly present practical aspects in the context of sample preparation and experimental protocols. With these fundamental concepts in place, the rootcause of some artefacts (e.g. non-uniform magnification, deviations of shape and dimensions of nanostructures, erroneous composition) observed in APT analysis of state-of-the-art semiconductor materials and devices will be discussed.