LEO
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
Vac-ion Pump
Column
“Upper
Valve”
Chamber
10-3—10-7 Torr
Column Valve
Electron gun
Turbo-molecular
pump
10-6—10-8 Torr
760—10-3 Torr
StageSample
Penning gage
Oil Filter
Exhaust
Pumping system for Leo W-filament SEM (actually LaB6)
Oil-sealed Rotary
Mechanical Pump
LEO
Leo 440i SEM
Column
Electron gun
Aperture adjustment micrometers
Chamber valve
Upper valve
Turbomolecular pump behind here
LEO
Administrative matters
• 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
• 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
Drop Down List Box and Tool Bar(nearly all SEM functions are mouse-controlled)
Beam on
Beam off
Standby
PumpVent Vacuum control
Left mouse button Middle mouse button
Roll mouse left to decrease value
Roll mouse right to increase value
Alternatively, double click on a box to enter data directly
LEO
Go!
• Turn on beam
• Turn up brightness
• Hopefully you will see something
• Optimize beam
• Backup plan– If you fail to get an image, under File/(run) Standard!
These are factory-installed parameters
LEO
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)
Beam location(Blue square)
Cursor!
Stage will move in direction of arrow when left mouse button is depressed
Speed increases with distance cursor is from beam
LEO
Pictoral explanation of gun shiftFilimentGun tilt
lens
lens
lens
aperature
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.
LEO
Optimize image• Start with low magnification• Look for dirt or some large feature• Move feature to center of screen• Go to reduced raster…Why?• Focus• Increase magnification…preferably 2-5X what
you will use for the image you record. Why?• 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
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