ccmr - ret 2008 week 5
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CCMR - RET 2008 WEEK 5. A type of electron microscope that images the sample surface by scanning it with a high-energy beam of electrons in a raster scan pattern. . SEM (scanning electron microscope). How does SEM work?. - PowerPoint PPT PresentationTRANSCRIPT
CCMR - RET 2008WEEK 5
SEM (scanning electron microscope)
• A type of electron microscope that images the sample surface by scanning it with a high-energy beam of electrons in a raster scan pattern.
How does SEM work?
• Electron beam interacts with the material, causing a variety of signals to be emitted-revealing details of the material’s shape, homogeneity and elemental composition.
SEM Images
• Low accelerating voltages– finer surface structure
images can generally be obtained.
SEM Images
• High accelerating voltages– the beam penetration
and diffusion area become larger, resulting in unnecessary signals being generated from within the specimen.
SEM Images
Lichen Unknown
Electron Microprobe
1149 Snee Hall
probelab.geo.umn.edu/electron_microprobe.html
A. Electrons are generated by heating a tungsten filament similar to the one in a light bulb.
B. Electrons pass through lenses that condense the beam, remove aberrations and focus the beam
C. The electrons hit the sample - This knocks out inner electrons in the sample - The atom is now in an excited state. An outer electron drops down to the inner energy level releasing energy in the form of x-rays at the same time.
D. X-rays are then reflected through a crystal
E. The reflected rays are then counted and recorded by a detector.
Electron Microprobe Uses• Non - destructive• Compositional Analysis
– Quantitative– Qualitative
• Precise X-Ray intensities• High Spectral Resolution
http://www.authorstream.com/Presentation/Janelle-19809-Electron-Beam-MicroAnalysis-Geol-619-1-History-Electrons-as-Entertainment-ppt-powerpoint/
Applications of the Electron Microprobe
Case Study One – What is under the fingernails?
Clay?
Paint?
Lichen?
SEM image
Insect Wing?
SEM image
Electron Microprobe Analysis
Since the fingernail is an organic compound, there was alarge carbon peak. Other elements such as calcium and sulfur
might be found in fingernails normally.
Other Applications of Electron Microprobe
GEOLOGY-
Chemical analysis of rocks, dating, plate tectonics
ArcheologyCompositional distinctions between 16th century ‘fac¸on-de-
Venise’ andVenetian glass vessels excavated in Antwerp, Belgium†
I. De Raedt,a K. Janssens*a and J. VeeckmanbaDepartment of Chemistry, University of Antwerp, Universiteitsplein 1, B-2610 Antwerp, Belgium.
E-mail: [email protected] Department of the City of Antwerp, Godefriduskaai 36, B-2000 Antwerp, Belgium
Received 29th October 1998, Accepted 10th December 1998At
JEOL 6300 SEM/EDX
Based on chemical analysis,50% of the glassware was from Italy
FORENSIC SCIENCESEMGSR
The SEM solution for AutomatedAnalysis and Classification of
Gunshot Residue
SEM/ Microprobe is used to analyze inorganic compounds in gunshot residue
STUDY POTENTIAL ELECTROCATALYSTS FOR FUEL CELLS
1. Sputter different concentrations of metals onto a substrate
(Based on lecture by Hector Abruna)
2. Perform Thermal imaging to determine areas of higher electrochemical activity
3. Use scanning electrochemical microscopy (SECM) to test sample’s ability to oxidize hydrogen/formic acid
and reduce oxygen.
Now we need to determine the chemical composition Of the product before bulk manufacture
Obtain composition with microprobe and Rutherford backscattering (RBS)
SEM-Observe texture and crystal grain size
GADDS-Determine crystal structure
Niobium/Tin Film Studies
Unannealed Sample- 2 to 1 Niobium to Tin
Element Line
Net Counts
Weight % Atom % Atom % Error
Compnd %
Nb L 64150 67.40 72.53 +/- 0.47 67.40 Nb M 0 --- --- --- --- Sn L 17107 32.60 27.47 +/- 0.33 32.60 Sn M 0 --- --- --- ---Total 100.00 100.00 100.00
Annealed Sample -
Oxygen accountedthe missing mass- the niobium was probably oxidized.
Large peak seen for Niobium. About 10% of mass unaccounted for.
Butterfly Wings-The Sequel-
Light Microscope Images
Butterfly Scales showing overlapping pattern
10µ
20µ
Individual scales showing ribbing
pattern
Light Microscope views
Fringe Scales Tips of Fringe scales
10 µ20 µ
Fringe Scales of Wing
100 µ 50µ
Optical Microscope -Transmitted Light
Optical Microscope – Reflected Light
Unpolarized vs Polarized Light
Wing Scale Unpolarized Light 50x objective lens
Wing Scale Polarized Light 50x objective
lens
10 µ 10µ