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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?.

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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. SEM (scanning electron microscope)
how does sem work
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
SEM Images
  • Low accelerating voltages
    • finer surface structure images can generally be obtained.
sem images1
SEM Images
  • High accelerating voltages
    • the beam penetration and diffusion area become larger, resulting in unnecessary signals being generated from within the specimen.
sem images2
SEM Images

Lichen

Unknown

electron microprobe

Electron Microprobe

1149 Snee Hall

slide8

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.

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

E.The reflected rays are then counted and recorded by a detector.

D.X-rays are then reflected through a crystal

probelab.geo.umn.edu/electron_microprobe.html

electron microprobe uses
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/

slide10

Applications of the

Electron Microprobe

slide13

Lichen?

SEM image

slide14

Insect Wing?

SEM image

slide15

Electron Microprobe Analysis

Since the fingernail is an organic compound, there was a

large carbon peak. Other elements such as calcium and sulfur

might be found in fingernails normally.

slide17

GEOLOGY-

Chemical analysis of rocks, dating, plate tectonics

slide18

Archeology

Compositional distinctions between 16th century ‘fac¸on-de-Venise’ and

Venetian glass vessels excavated in Antwerp, Belgium†

I. De Raedt,aK. Janssens*a and J. Veeckmanb

aDepartment of Chemistry, University of Antwerp, Universiteitsplein 1, B-2610 Antwerp, Belgium.

E-mail: [email protected]

bExcavation Department of the City of Antwerp, Godefriduskaai 36, B-2000 Antwerp, Belgium

Received 29th October 1998, Accepted 10th December 1998

At

JEOL 6300 SEM/EDX

Based on chemical analysis,

50% of the glassware was from Italy

slide19

FORENSIC SCIENCE

  • SEMGSR

The SEM solution for Automated

Analysis and Classification of

Gunshot Residue

SEM/ Microprobe is used to analyze

inorganic compounds in gunshot residue

slide20

STUDY POTENTIAL ELECTROCATALYSTS

FOR FUEL CELLS

(Based on lecture by Hector Abruna)

Sputter different concentrations

of metals onto a substrate

slide21

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.

slide22

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

slide25

Annealed Sample -

Large peak seen for Niobium.

About 10% of mass unaccounted for.

Oxygen accounted

the missing mass- the niobium was probably oxidized.

butterfly wings

Butterfly Wings

-The Sequel-

light microscope images
Light Microscope Images

20µ

Butterfly Scales showing overlapping pattern

10µ

Individual scales showing ribbing pattern

light microscope views
Light Microscope views

20 µ

10 µ

Fringe Scales

Tips of Fringe scales

fringe scales of wing
Fringe Scales of Wing

100 µ

50µ

Optical Microscope -Transmitted Light

Optical Microscope – Reflected Light

unpolarized vs polarized light
Unpolarized vs Polarized Light

10 µ

10µ

Wing Scale Unpolarized Light 50x objective lens

Wing Scale Polarized Light 50x objective lens

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