Advanced Analytical Techniques in TEM and SEM
Two-day Seminar Presented by JEOL, University of Maryland, and Gatan, Inc.
Register now: http://ter.ps/3wb
Day 1 - Tuesday, November 5, 2013
8:00 - 9:00 Registration, Continental Breakfast
9:00 - 9:55 Aberration Corrected Electron Microscopy: Structure Determination and Chemistry on the Atomic Scale - Dr. Thomas Isabell, JEOL
Few electron optical inventions have revolutionized the TEM/STEM as profoundly as the spherical aberration (Cs) corrector. With Cs correctors the sub-Ångstrom imaging barrier has been passed, and fast atomic scale spectroscopy is possible. In addition to improvements in resolution, Cs correctors offer a number of other significant improvements and benefits. This next generation of microscopes can determine the atomic structure of a specimen, and when combined with energy loss spectrometers and Energy Dispersive Spectrometers (EDS), the exact chemistry of that atomic structure is simultaneously determined. This talk will show how this microscope/detector combination can be used to solve a variety of materials issues at the sub-Ångstrom level.
10:00 - 10:55 Review of EELS and EFTEM Fundamentals - Ray Twesten, Gatan
Electron energy loss spectroscopy (EELS) is the analysis of the energy distribution of electrons that have passed through the specimen and interact inelastically with it. It is a powerful technique that provides information on elemental composition and electronic structure in a particular area of the material. EELS represents the basis for energy filtering transmission electron microscopy (EFTEM) where the use of an imaging filter as spectrometer is required. EFTEM provides rapid elemental maps to identify unknown elemental distributions and give some information on the composition. The lecture will review some of the physics behind the generation of the EELS signal, how it is measured and more importantly how specimen information can be extracted from the EELS signal.
11:00 - 11:15 A.M. Break
11:15 - 12:10 STEM EELS and EFTEM Spectrum Imaging (SI) - Ray Twesten, Gatan
An EELS spectrum imaging (SI) is obtained by scanning a finely focused electron probe along a line or an area. This region of interest is identified within a survey image and a raster is defined over that region. An entire EELS spectrum is taken at each pixel of the raster. The advantage of a spectrum mapping over point spectrum measurements is the possibility of recognizing trends in the EELS transition in relation to the position of microstructural features in the sample. EELS SI allows EELS to gain spatial resolution. The EFTEM SI approach is rather different from EELS SI. Here, a series of images is acquired and the position of the slit for each image is scanned over a certain region in the EELS spectrum. In addition to pure filtered images, EFTEM SI stack contains spectroscopy information. An EELS spectrum can be extracted everywhere across the stack of images and the background can be placed accordingly giving the best fit. The lecture will describe the differences between the two approaches, how to create elemental profiles and quantitative maps.
12:15 - 1:30 Complimentary Lunch
1:30 - 2:25 Recent Advances in FEG SEM that Improve Spatial Resolution for Both Imaging and Microanalysis - Vern Robertson, JEOL
Recent advances in FEG gun technology, lens design, beam control (deceleration & filtering), detector design & spectrometer design have pushed the FEG SEM into imaging and analysis modalities that only a few years ago would have been unimaginable. For decades the limits of resolution for microanalysis were governed by the unbreakable link between probe size and probe current and the inability to get enough X-ray data from a small enough volume within a bulk sample. Applications examples from low kV, high spatial resolution microanalysis, STEM imaging at the single digit Angstrom level and STEM microanalysis will be discussed along with surface sensitive imaging and microanalysis with depth resolution approaching that of scanning Auger.
2:25 - 3:00 Recent Examples of Analytical (S)TEM Applications - Ray Twesten, Gatan
Computer automation, high-efficiency spectrometers, and high-speed detectors in combination with modern electron microscopes allow the routine acquisition of information rich, multi-dimensional data sets in a simplified, automated manner. While software and automation allows routine acquisitiion of these data sets, obtaining quality data requires the understanding of the limits and tradeoffs inherent in the experiment. We will reference several case studies that serve to illustrate the strength and potential pit falls of these techniques with particular emphasis on the simultaneous acquisition of complementary signals (EELS, EDS, CL, Diffraction,....) in the (S)TEM.
3:00 - 3:40 Low Accelerating Voltage, X-ray Microanalysis: Benefits and Challenge - Peter McSwiggen, McSwiggen & Associates
The development of the field emission (FE) electron gun has made it possible to generate extremely high electron densities and as a result, an electron beam that is up to a tenth the diameter of the conventional thermionic emission electron gun using a W filament or a LaB6 tip. Now the challenge is to be able to take advantage of this smaller electron beam to provide X-ray analyses of more comparable size areas. Using the typical operating conditions for X-ray microanalyses (15-25kV accelerating voltage), the electron beam scattering within the sample results in an analysis of up to a few microns. However working at a low accelerating voltage, the amount of scatter is greatly reduced. The optimum accelerating voltage that will produce the smallest analytical volume is typically around 5-8 kV, which in many materials will result in an analytical volume in the 200 500 nm range. Working at low accelerating voltages, however, can produce a new set of challenges, include: (1) fewer available X-ray lines, (2) fewer X-rays are produce for a given beam, and (3) surface coatings have a greater impact on the measured counts. Low voltage analysis has become the challenge that light element analysis has been in the past. However, as with light element analyses, these challenges can be overcome allowing for good quality, quantitative analyses of sub-micron features.
3:45 Q&A (Stump the Microscopists!) and Preview of Day 2 - JEOL/Gatan/UMD
4:00 Adjourn for the Day
Day 2 - Wednesday, November 6, 2013
Practical Applications of Lectures from Previous Day
8:00 - 9:00 Registration, Continental Breakfast
9:00 - 9:45 Basic Setup of TEM - Dr. Thomas Isabell, JEOL
9:55 - 10:30 Basic EELS and EF-TEM Data Acquisition and Analysis - Ray Twesten, Gatan
10:30 - 10:45 Break
10:45 - 11:35 STEM EELS Acquisition - Ray Twesten, Gatan
11:40 - Adjourn
Afternoon: Optional breakout for EELS users.