LEO

Jon Paul Johnson’s MontageDuctile Iron Images

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!)

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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

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Leo 440i SEM

Column

Electron gun

Aperture adjustment micrometers

Chamber valve

Upper valve

Turbomolecular pump behind here

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Leo SEM: rear of column

Vac-ion pump

Everhard-Thornley Detector

Gun

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EDS side of SEM

LN2 tank

Beam blanker

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Oil-sealed rotary mechanical pump

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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.

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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.)

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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

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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

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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.

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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

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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

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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

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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

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Use when OptiBeam is off

OptiBeam on

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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.

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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• 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

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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”

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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

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Check “Export/Photo setup” to assure it is not set to “HRRU”!