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Electron Microscopy Facility
Subsidiary of the Research and Graduate Studies Office of the AVP

Verios SEM Startup

By Paul Minson,
May 05, 2023 02:01 PM

Verios G4 UC Operation

Getting Started

Your sample should be securely attached and grounded to a specimen stub that is 1/2” or larger having a 1/8”-diameter post.

Loading the Sample

1. Vent the chamber by pressing the “Vent” button on the Beam Control panel’s Vacuum pane.
2. Move the stage to a Load position and place sample on the stage.

  • Check sample height using the sample height gauge. Top of sample must be below the overhang but above the “4” mark. If it is not, sample holder height must be adjusted.
  • Tighten the set-screw.

3. Gently close the chamber door and pump the chamber by clicking the “Pump” on the Beam Control panel’s Vacuum pane. Make sure the chamber door is fully closed!
4. While the microscope is pumping, it will take a Nav-Cam image. Wait for the process to complete and the stage to return to its previous position.
5. Move the stage to the Centered position.

Positioning the Sample *Critical for avoiding damage to the microscope!*

6. Turn on the Beam by clicking “Beam On” button in the Beam Control panel’s Column pane.
7. Set beam voltage to 5 kV and beam current to 50 pA or 0.1 nA using the toolbar drop-downs.

  • Select the ETD detector, set the dwell to 50 ns and the scanning resolution to 1536x1024, select 4-frame averaging, and un-pause the imaging in the top left imaging window.

8. Locate the highest point of your sample, and focus on it at 1,000x – 2,000x magnification.
9. Link the Z axis to Free Working Distance by clicking the Link Z to FWD button in the toolbar.
10. Move the stage Z-axis position to 4.3 mm using the Navigation panel’s Stage pane.
11. Re-focus on the sample at around 5,000x – 10,000x and then re-link the Z to FWD.
12. Move the stage Z-axis position to 4.1mm using the Navigation panel’s Stage pane.

Setting up the Beam

13. Select the desired beam voltage and beam current using the toolbar drop-downs.
14. Check the beam crossover in the Direct Adjustments panel’s Direct Adjustments pane

  • On the beam tab click the “Crossover” button to show the crossover. Center the crossover on the crosshairs using the Source Tilt adjuster.
  • Click the “Crossover” button again to return to normal imaging.

15. Check the objective aperture centering using the “Lens Modulator” button on the Direct Adjustments pane

  • Locate and center a high-contrast feature on the sample at a magnification around 10,000x.
  • On the beam tab click the “Lens Modulator” or “HV Modulator” button to start the oscillation.
  • Eliminate the oscillating movement of the image using the Lens Alignment adjuster.
  • Click the “Lens Modulator” or “HV Modulator” button again to return to normal imaging.

16. Locate your area of interest, adjust focus and stigmation, and then start collecting images!

  • Focus and stigmate at one-and-a-half to two times the highest magnification you will image at.
  • To stigmate: 1. Find center focus, 2. Stig X, 3. Stig Y, 4. Find center focus, then repeat if needed.

Unloading the Sample

1. Vent the chamber by pressing the “Vent” button on the Beam Control panel’s Vacuum pane.
2. While venting: after stage moves to lowest height, move the stage to a Load position.
3. Open chamber door, remove sample(s), then gently close the chamber door and pump the chamber down by clicking the “Pump” on the Beam Control panel’s Vacuum pane. Make sure the chamber door is fully closed!  

UC Mode Usage (Unicolor Mode, i.e., monochromated beam mode)

Needs beam energy 5 keV or less and beam current 0.1 nA or less. Improves resolution at low beam energies when not using beam deceleration (stage bias).

Detector Summary (SE=secondary electron, BSE=backscattered electron, OPT=optical)

ETD (SE) – Everhart-Thornley detector. Detects SEs

  • Captures SE signal in chamber, good for topographical contrast

ETD (BSE) – Everhart-Thornley detector. Detects BSEs
TLD-SE – through-the-lens detector. Detects SEs
TLD-BSE – through-the-lens detector. Detects BSEs
MD – Mirror Detector. Detects BSEs (especially if suction tube is negatively biased).

  • Solid state detector, captures BSE signal in column, good for compositional contrast.
  • Needs slow scan; 3 keV beam energy is best. Needs stage bias to work below 2 keV beam energy.Sample must not be tilted when using stage bias.

ICD – In Column Detector, solid state detector, above the mirror plate and closest to beam.

  • Detects highest energy BSEs: best Z contrast & lowest topographical contrast.
  • Use in Immersion mode without beam deceleration (stage bias) at 10 keV beam energy or higher and 0.1 nA beam current or higher for best BSE imaging performance.
  • Use in Immersion mode with beam deceleration (stage bias) at low beam energies (<=5 keV) for the highest resolution SE imaging detector on the microscope. Sample must not be tilted when using stage bias. ICD is very sensitive to sample charging in this mode at low beam energies!

ABS – angular backscatter detector. Detects BSEs

  • Needs a slow scan, and beam current of 25 pA minimum (50 pA or higher is best).
  • 3 keV beam energy or higher is best. Needs stage bias to work below 2 keV beam energy.
  • Can do topographical imaging.

CBS – conical backscatter detector. Detects BSEs

  • Needs a slow scan, and beam current of 25 pA minimum (50 pA or higher is best).
  • 3 keV beam energy or higher is best. Needs stage bias to work below 2 keV beam energy.
  • Needs a slow scan.

CCD – charge-coupled-device, infrared OPT image of chamber

  • Good for seeing sample position and motion relative to the pole piece.

STEM 3+ - scanning transmission electron detector

  • Needs TEM sample, special holder on stage, and high beam energy (20+ kV).

Nav-Cam – top-down OPT image of specimen holder

  • Used to take static image of specimen holder for navigation on specimen(s).