Advanced Applications of Microscopy (SEM and TEM), Surface Analysis, NMR, Mass Spectrometry, and Direct Write E-Beam Lithography
Sponsored by JEOL
Tuesday, Sept 18, 2018
36-428, Haus Room (4th floor)
50 Vassar St.
Brief overview of the day's talks
Advanced Aberration Correction: Atomic Resolution (S)TEM Imaging and Microanalysis from 30 kV to 300 kV
Choosing the correct microscope high tension, or accelerating voltage, is an important experimental consideration for TEM imaging and microanalysis. Higher accelerating voltages naturally lead to better spatial resolution for imaging, but will also lead to accelerated specimen damage. For microanalysis, lower accelerating voltages mean more beam spreading and worse spatial resolution, but also enhanced microanalysis cross sections for EDS and EELS. A new generation of aberration corrected microscopes gives the user the flexibility to operate over a wide range of high tension with unprecedented imaging and chemical spatial resolution. This means that on the same instrument, the voltage can be dialed in for a given experiment and readily changed as different experimental needs arise. The addition of a cold field emission gun, advanced aberration correctors and advanced detectors only enhances operation at both high and low voltages, further adding to instrument flexibility.
Low Voltage FESEM Imaging and Microanalysis (Doing What Used to Be Impossible)
In just the last few years there has been a quantum leap in the ability of the scanning electron microscopes (SEM and EPMA) to observe and chemically analyze a wide variety of materials form various fields of interest and have drastically increased analysts capabilities. Field Emission (FEG) SEMs provide the capability to create a very small probe diameter (high resolution imaging) at very low accelerating voltage (high resolution microanalysis) with high beam currents required for analysis and with exceptional surface detail and reduced beam specimen interaction in a bulk sample with previously unattainable nanometer scale resolution at landing voltages as low as 10V allowing the examination of nonconductive materials both for imaging and analysis. In years past these samples would have required the application of a conductive coating lengthening the sample prep process and possibly obscuring surface sensitive information. However, these extremely low voltages come with some clearly defined sample preparation and handling procedures.
Advances in X-ray spectroscopy, both in Energy Dispersive Spectroscopy (EDS) and a new novel Wavelength Dispersive Spectrometer (WDS) have also pushed the boundaries to higher mag, lower voltage and lower X-ray energy (soft X-ray) analysis opening up new avenues for specimen observation and analysis. More & more we are seeing other accessories like EBSD, TKD, CL, etc. being integrated into the everyday operation of the electron microscopes.
These new state-of-the-art microscopes, detectors and spectrometers today allows one to overcome many of the historical limitations associated with low kV imaging and microanalysis. HOWEVER, there are some considerations that may not have been thought about in the past. Some case studies and examples of the good things (and some of the bad) that can result from ultralow kV imaging and analysis will be presented.
As you will see from the images and analyses, ultralow kV and or ultra-high spatial resolution is a VERY POWERFUL tool, and as with all powerful tools, it needs to be used with caution (or at least with keeping an eye out for the non-intuitive). Applications examples of previously “impossible tasks” will highlight how these new generations of microscopes & spectrometers have pushed the boundaries of electron microscopy for basic research and failure analysis
SAM, SXES, EPMA (An Alphabet Soup of FE Microanalysis)
All of the advantages of field emission discussed earlier have migrated in the microanalysis world for both Scanning Auger and Electron Microprobes providing a significant improvement of not only imaging resolution but spatial resolution for microanalysis well below the old limit of ~1micron. Improvements in detectors including the now ubiquitous SDD EDS have brought huge advances in microanalysis. A completely new type of x-Ray spectrometer that analyses very low energy x-Rays (soft x-Rays) with ultra ,ultra-high spectral resolution and chemical state mapping will be presented in detail with applications examples. New software allows a further improvements providing data that was very time consuming to acquire in the past.
Development of Laser Ablation Direct Analysis in Real Time Imaging Mass Spectrometry (LADI-MS)
Imaging mass spectrometry has expanded in recent years to include the use of ambient ionization sources for the detection of small-molecules. Most current techniques require the use of solvent, high vacuum, and/or the application of a matrix. These steps, however, can complicate the ability to detect and map the spatial distribution of small-molecules. We show that using an approach that integrates a DART ambient ionization source, a UV laser and a TOF mass spectrometer, small-molecule spatial distribution maps can be acquired for a broad range of sample types, with no sample pretreatment requirements. The utility of the LADI-MS method for facile and routine analysis of a variety of sample types is demonstrated for mapping the spatial distribution in plant tissue of small molecules involved in biochemical cascades, investigating the chemical content of vessels in endangered wood species, establishing exposure to plant-based psychoactive substances through small-molecule mapping of fingerprints, detecting forgery through mapping of inks on paper, analyzing small molecules in mouse brain tissue and determining the distribution of carcinogens in coffee beans.
And Now for Something Completely Different…Masses, Materials and More
Mass spectrometry is one of the fastest-growing fields in analytical chemistry, having evolved from GC/MS and electron ionization to set of technologies that cover an incredibly broad range of applications. Classic techniques like field ionization have evolved from tricky niche technologies to reliable and easy-to-use analytical methods. Ambient ionization now allows us to obtain a mass spectrum for almost anything instantaneously and at atmospheric pressure, and mass spectrometry imaging provides complementary information to that obtainable by microscopy. How we use these techniques to identify unknown substances and materials is the subject of this talk.
Atomic Resolution Spectroscopy & Other Unlikely Data from an Uncorrected Workhorse TEM/STEM
Recent advances in aberration-corrected electron microscopy have enabled the acquisition of data that was once thought impossible, including sub-angstrom image resolution and atomic-resolution EELS and EDS maps. Owed to new cold field emission guns (CFEG), advanced EDS detector capabilities, and column stability, similar atomically-resolved data can now be realized in uncorrected systems as well. This talk will focus on the wide range of applications now possible on JEOL’s newly released 200 kV S/TEM. The instrument, outfitted with a CFEG, dual large-area silicon drift EDS detectors, and an advanced EELS system, excels at S/TEM imaging, analytical spectroscopy, and 3D tomography applications. The narrow energy spread of the CFEG enables electronic fine structure and oxidation state analysis to be carried out with simultaneous EDS and EELS mapping, down to the atomic scale. Additionally, the reduced effects of chromatic aberration of the CFEG allow for enhanced low voltage analysis, without sacrificing probe current or image resolution. These features, combined with the increased column stability, redesigned scan system, and improved auto-functions, make this a highly-functional workhorse S/TEM, with capabilities unprecedented for an uncorrected system.
September 18, 2018