2012 Spring SEM Lecture 01
-
Upload
ramon-relosa -
Category
Documents
-
view
220 -
download
0
Transcript of 2012 Spring SEM Lecture 01
-
8/3/2019 2012 Spring SEM Lecture 01
1/49
Basic Principles
Presented by Joven Calara Research Engineer, Metallurgy
Scanning ElectronMicroscopy
-
8/3/2019 2012 Spring SEM Lecture 01
2/49
Simple Magnifiers
Raindrop
-
8/3/2019 2012 Spring SEM Lecture 01
3/49
Simple Magnifiers
Raindrop
Simple lens
- hand magnifier
Magnification to ~10x
-
8/3/2019 2012 Spring SEM Lecture 01
4/49
Compound Magnifiers - Microscope
Maximum magnification ~1000x - WHY?
-
8/3/2019 2012 Spring SEM Lecture 01
5/49
Light Microscope limits of magnification
Green algae 400X magnification
-
8/3/2019 2012 Spring SEM Lecture 01
6/49
Light Microscope limits of magnification
Green algae 800X magnification
-
8/3/2019 2012 Spring SEM Lecture 01
7/49
Visible Light Spectrum
Wavelength () 400 700 nm
-
8/3/2019 2012 Spring SEM Lecture 01
8/49
Optical microscopes
Optical microscopes resolution limited bywavelength of light
Abbes Law;Maximum resolution = /2 = 200 nm
-
8/3/2019 2012 Spring SEM Lecture 01
9/49
Image of point light source the Airy disc
-
8/3/2019 2012 Spring SEM Lecture 01
10/49
Image of point light source the Airy disc
Airy disk
-
8/3/2019 2012 Spring SEM Lecture 01
11/49
Image of point light source the Airy disc
Airy disk
Airy disks and resolution
-
8/3/2019 2012 Spring SEM Lecture 01
12/49
Objects smaller than 500 nm
Viruses, as small as 5 nm
-
8/3/2019 2012 Spring SEM Lecture 01
13/49
Objects smaller than 500 nm
Viruses, as small as 5 nm
Smoke or soot particles
Colloids (very fine particles) Milk !
-
8/3/2019 2012 Spring SEM Lecture 01
14/49
Objects smaller than 500 nm
http://www.foodsci.uoguelph.ca
-
8/3/2019 2012 Spring SEM Lecture 01
15/49
Wavelengths shorter than 200nm needed
-
8/3/2019 2012 Spring SEM Lecture 01
16/49
Wavelengths shorter than 200nm needed
, nm Why not
Ultraviolet 100 200 Glass is opaque to UV
X-rays 0.1 100 Glass cant focus x-rays
Gamma rays < 0.1 Ionizes everything
By early 1900, new approaches to microscopy were desperately
needed.
-
8/3/2019 2012 Spring SEM Lecture 01
17/49
A Different Method of Magnification - Mapping
Mapping ; one-to-one correspondence betweenfinite number ofthe elements of two areas. Modern implementation is scanning.
Example; a small photograph mapped onto a building wall mural
scanning photo into picture elements (pixels) and enlarged
reproduction of the pixels. Each pixel a single color/brightness.
-
8/3/2019 2012 Spring SEM Lecture 01
18/49
20 cm x 20 cm
section of LCD
Subdivide this into pieces,
each to match a pixel on LCD
-
8/3/2019 2012 Spring SEM Lecture 01
19/49
A section of an LCD screen
-
8/3/2019 2012 Spring SEM Lecture 01
20/49
A section of an LCD screen
-
8/3/2019 2012 Spring SEM Lecture 01
21/49
Pixel count = 4 per mm
-
8/3/2019 2012 Spring SEM Lecture 01
22/49
20 cm x 20 cm
section of LCD
Subdivide this into pieces,
each to match a pixel on LCD
screen
800 pixels high and wide
-
8/3/2019 2012 Spring SEM Lecture 01
23/49
20 cm x 20 cm
section of LCD
Black and white picture, pixel attribute
is brightness only. Laser beam scan OK.
800 pixels high and wide
= laser spot diameter
d cm
-
8/3/2019 2012 Spring SEM Lecture 01
24/49
20 cm x 20 cm
section of LCD
Black and white picture, pixel attribute
is brightness only. Laser beam scan OK.
800 pixels high and wide
= laser spot diameter
d cm
d, cm magnification laser spot dia.
5 4x 0.063 mm
0.2 100x 0.0025 mm
0.02 1000x 250 nanometers
0.01 2000x 150 nm
Light beams at >>1000x
-
8/3/2019 2012 Spring SEM Lecture 01
25/49
Electron beams (electrical discharges)
Lightning electron beamin air
Lightning Globe toy
electron beams in partial
vacuum
-
8/3/2019 2012 Spring SEM Lecture 01
26/49
Early Electron Beam Device Crookes Tube
Cathode ray tube
Cathode ray deflection with
magnetic fields
-
8/3/2019 2012 Spring SEM Lecture 01
27/49
Early oscilloscope (1897)
First example of beam scanning, just on a
single line. Input signal appears as waveform.
-
8/3/2019 2012 Spring SEM Lecture 01
28/49
Cathode ray tube (CRT, 1907)
Raster scanning
-
8/3/2019 2012 Spring SEM Lecture 01
29/49
Modern Electron Beam Devices
Television - Computer monitors
CRT monitor ~1980
TV
Black and white TV - ~1950
-
8/3/2019 2012 Spring SEM Lecture 01
30/49
Technological skills in place by early 1900;
Generation of electron beam
Focusing of the beam
Scanning or rastering (scanninge.g. left to right, then down a bit,
repeat scan)
-
8/3/2019 2012 Spring SEM Lecture 01
31/49
Simplified sketch of electron scanning optics
-
8/3/2019 2012 Spring SEM Lecture 01
32/49
Simplified sketch of electron scanning optics
Laser scanning
detected signal = reflected light
E-beam scanning
detected signal = ? ? ? ?
-
8/3/2019 2012 Spring SEM Lecture 01
33/49
Electron beam solid interaction
-
8/3/2019 2012 Spring SEM Lecture 01
34/49
Secondary electrons,
-
8/3/2019 2012 Spring SEM Lecture 01
35/49
The Scanning Electron Microscope
T
-
8/3/2019 2012 Spring SEM Lecture 01
36/49
Electron Imaging Effect of Surface Topology
(Detector overhead sample)
T
-
8/3/2019 2012 Spring SEM Lecture 01
37/49
Electron Imaging Effect of Surface Topology
(Detector overhead sample)
T
Chrysanthemum pollens
-
8/3/2019 2012 Spring SEM Lecture 01
38/49
Small area on
specimen
Display device photo print or monitor
Magnification by the SEM
Effect of Probe (Beam Spot) Size
-
8/3/2019 2012 Spring SEM Lecture 01
39/49
Small area on
specimen
Display device photo print or monitor
Magnification with wide probe size (laser spot?)
-
8/3/2019 2012 Spring SEM Lecture 01
40/49
Wavelength of electron beams theDe Broglie Equation
Light can behave as waves (lightwaves), or as particles (photons).
De Broiglie proposed the converse is also true. Electrons have wave
properties.
De Broglie Equation adaptedto SEM
= h/sqrt(2meV)
= 1.23/sqrt(V) nanometers
At V = 10,000 volts, = 0.0123 nanometers
De Broglie Equation adaptedto SEM
= h/sqrt(2meV)
= 1.23/sqrt(V) nanometers
At V = 10,000 volts, = 0.0123 nanometers
h (Plancks constant) = 6.63x10-34 Js
m(electron mass) = 9.11x10-31 kg
e (electron charge) = 1.6x10-19 C
-
8/3/2019 2012 Spring SEM Lecture 01
41/49
SEM resolution
Theoretical 0.01 nm
Development lab grade 0.1 nm
High end 1.0 nm Typical 3 nm (ca. 300,000x)
Typical magnifications routine 200-8000x
-
8/3/2019 2012 Spring SEM Lecture 01
42/49
Depth of Field how deep is the field in sharp focus
Optical microscope SEM
Tungsten filament
-
8/3/2019 2012 Spring SEM Lecture 01
43/49
-
8/3/2019 2012 Spring SEM Lecture 01
44/49
Characteristic X-rays;
Elements Chemical Analysis
-
8/3/2019 2012 Spring SEM Lecture 01
45/49
Characteristic X-rays;
Elements Chemical Analysis
-
8/3/2019 2012 Spring SEM Lecture 01
46/49
Ductile Iron
-
8/3/2019 2012 Spring SEM Lecture 01
47/49
-
8/3/2019 2012 Spring SEM Lecture 01
48/49
JEOL JSF-6400 Scanning Electron Microscope of SLCC
-
8/3/2019 2012 Spring SEM Lecture 01
49/49
Hitachi TM3000 Scanning Electron Microscope