Transcript Technical Objective • To train you to use the electron

Technical Objective
• To train you to use the electron
microscopes on lower campus
• Start with the Leo 440i
– We control it!
– It’s currently running
– Once you have learned the concepts on one
microscope, in principle everything else is
“knobololy” (Figuring out where the knobs
are that control the feature you want to use.)
– It’s not easy or expensive to break (please
don’t prove me wrong!)
LEO
Electron gun
“Upper
Valve”
Vac-ion
Pump
Column
10-6—10-8
Torr
Column Valve
Pumping system for
Leo W-filament SEM
(actually LaB6)
Chamber
Penning
gage
Sample
Turbomolecular
pump
10-3—10-7
Torr
Exhaust
Oil Filter
Stage
760—10-3
Torr
Oil-sealed
Rotary
Mechanic
al Pump
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Leo 440i SEM
Upper valve
Electron gun
Column
Chamber valve
Aperture
adjustment
micrometers
Turbomolecular
pump behind here
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Leo SEM:
rear of
column
Gun
Vac-ion
pump
EverhardThornley
Detector
LEO
EDS side
of SEM
LN2 tank
Beam
blanker
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Oil-sealed rotary
mechanical pump
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Administrative matters
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Nothing in life is free
Log onto the SEM with the sheet on the desktop
Enter your name
Enter the name and contact information of
whoever will be paying
Record how many times you coated samples
Click on “View/Status”. Enter the filament
lifetime when you start.
Enter the time of day when you start.
Repeat the last two steps when you finish.
LEO
Notes on the computer
• The SEM is about 15 years old. It runs on
a 66 MHz 486 under Windows 3.11.
• Plan on having to reboot at least once per
day.
• In windows 3.11 you cycle among active
applications with ALT TAB. (Hold down
ALT; every time you hit TAB, it cycles one
application.)
LEO
Getting started with the Leo
• Typical conditions when you walk in:
– Ion pump is running
– Chamber is under vacuum
– “Upper valve” (gun valve) is closed
– Column valve is open
– All pumps are running
LEO
Sample Mounting
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Leo uses mounting stubs with 1/8” shafts
Carbon tape (double sticky) is simplest
Carbon dots have lower vapor pressure
Multiple samples can be mounted on turret
Make a drawing in your research notebook of
the locations of your samples on the turret
• Single mount is easiest for tilting
• Vertical mount is also an option
• Tighten gently with Allen wrench; ditto for
sample holder on stage
LEO
To insert your sample
• Check vacuum
– Stage/vac
– Vacuum status
• Chamber pressure should be 10-5 – 10-6 Torr
• Column pressure should be few x 10-7 Torr
• Close column valve
• Vent (Stage/vac, Specimen change or right
yellow arrow)
• Insert sample. Remember where samples are!
• Close and latch door. Do not overtighten!
• Pump (Stage/vac, Specimen change or right
yellow arrow)
• After the pressure goes below 10-4 Torr you may
open the column valve and turn on the beam.
LEO
LEO
Drop Down List Box and Tool Bar
(nearly all SEM functions are mouse-controlled)
Left mouse button
Beam on
Beam off
Alternatively,
double click on a box
to enter data directly
Standby
Pump
Vent
Middle mouse button
Vacuum control
Roll mouse left to decrease value
Roll mouse right to increase value
LEO
Go!
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Turn on beam
Turn up brightness
Hopefully you will see something
Optimize beam
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Decide on operating parameters
• 40 kV for highest resolution
• 20 kV for EDX
• Low voltage for optimum topography and
least damage
• 100 pA for good resolution
• 300 pA for EDX for better signal-to-noise
• 25 mm WD for EDX
• 7 – 8 mm WD for maximum resolution
LEO
Center of Stage
(Red square)
Stage will move in
direction of arrow
when left mouse
button is
depressed
Speed increases
with distance
cursor is from
beam
Beam location
(Blue square)
Cursor!
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OptiBeam on
Use when
OptiBeam
is off
LEO
Pictoral explanation of gun shift
Filiment
Gun tilt
lens
lens
aperature
lens
With the gun shift centered, the electron beam heads straight down the column.
The image is brighter and can also be focused better. Otherwise the image
moves when you change focus.
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Center filament image with “Tilt” option
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Adjust beam shift when OptiBeam is turned on
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Voila! An image!
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Optimize image
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Start with low magnification
Look for dirt or some feature
Move feature to center of screen
Go to reduced raster
Focus
Increase magnification
Focus
Iterate
Full screen image
LEO
Saving an image
• Get good quality image
– 2 minute scans over a few kX
– Faster scans at lower magnification
• Under “Image/Noise reduction”, click on
“Freeze at end”
LEO
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Saving images, cont’d
• Under “File/Export tiff”, choose e:\ as the
destination. The E:\ drive is mapped to the
support PC that is next to the machine. From
this machine you can use a USB memory stick
or transfer files through the internet-- web mail or
file transfer.
• Enter a filename: 6 characters (related to your
sample) + 2-digit counter (00)
• All students need to bring their own USB
stick; files are approximately 1 MB
LEO
Check
“Export/Photo
setup” to assure
it is not set to
“HRRU”!
LEO