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 LichenUnknown

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 Geol History-Electrons-as-Entertainment-ppt-powerpoint/

Applications of the Electron Microprobe

Case Study One – What is under the fingernails?

Paint?

Lichen? SEM image

Insect Wing? SEM image

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.

Other Applications of Electron Microprobe

GEOLOGY- Chemical analysis of rocks, dating, plate tectonics

Archeology Compositional distinctions between 16th century ‘fac¸on-de- Venise’ and Venetian glass vessels excavated in Antwerp, Belgium † I. De Raedt,a K. Janssens*a and J. Veeckmanb aDepartment of Chemistry, University of Antwerp, Universiteitsplein 1, B-2610 Antwerp, Belgium. 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

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

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 % Error Compnd % Nb L / Nb M Sn L / Sn M Total

Annealed Sample - Oxygen accounted the 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 ScalesTips of Fringe scales 10 µ 20 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