Notre Dame extended Research Community NANOWeek: The Power of Microscopes Optics Visible light...

Notre Dame extended Research Community

NANOWeek:The Power of Microscopes

•Optics•Visible light•Optical microscopes and telescopes•Scanning electron microscope

The Metric Scale is relevant to LIFE

1m = 2nd grade child 2.1m = Shaquille O’Neill 1/100m = 1 cm =~ width of pinky finger 1/1000m = 1 mm =~width of a dime 1/1,000,000 = 1 um (micron) 1/1,000,000,000 = 1nm

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The Nanometer Scale:

One inch equals 25.4 million nanometers. A sheet of paper is about 100,000

nanometers thick. A human hair measures roughly 50,000

to 100,000 nanometers in diameter. Your fingernails grow one nanometer

every second.

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A prism can separate white light into all the colors of the rainbow

Image taken from www.opticalres.com

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How do we see?

target

source

detector…and often you’ll need a lens

Magnifying Glass

Magnification: 2-10x (Loupes 30x)

One lens (Many Lenses and Prisms)

Usually a biconvex lens - both sides are convex

Focal Length

MagnifiedRight Side Up

ShrunkUpside Side Up

Focal Length

Activity: Assemble the Telescope!

Arrrrgh!

Microscope

Light Source

Stage and Sample

Objective Lens

Ocular Lens (Eyepiece)

Magnification

Objective Lenses4x Magnification10x Magnification40x Magnification100x Magnification

10x Magnification

Total Magnification:40x, 100x, 400x, 1000x

Other techniques: Feature Size

Digital Microscope

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Example Image

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Scale

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What Comes Next?

How do we view things smaller than the wavelength of light?

What do we actually “see” when we use such techniques?

http://www.mrs.org/s_mrs/doc.asp?CID=1803&DID=171434

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Basic SEM Idea

e-e-

e-

e-

e-

e-

e-

e-

e-

e-e-

Some are absorbed

Some are “reflected”

Some is absorbed

Some light is “reflected”

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Water Hose and Splash

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The “Splash”

http://www4.nau.edu/microanalysis/Microprobe-SEM/Signals.html

Primary electrons come from the beam

Some electrons scatter back (BSE), and they

move very fast

Other secondary electrons (SE) are

dislodged and move more slowly

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The Electron Beam Column

http://bioweb.usu.edu/emlab/TEM-SEM%20Teaching/How%20SEM%20works.html

Beam created from heated filament

Beam travels through a vacuum

Electro-magnetic fields act as lenses

Scattered and “secondary” electrons are detected

Electron beam hits the sample in a precise

location

Beam scans back and forth

Scanning Electron Microscope (SEM)