FEI Tecnai G2 F20 - User Manual

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FEI Tecnai G
2
F20 Operating Procedures
(6/01/2017)
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1. Startup
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1. Sign-up in the microscope log-book
2. Startup the software if not already running: Start the software in this
sequence:
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1. Tecnai User Interface
2. Digital Micrograph
3. TIA (TEM Imaging and Analysis)
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3. Check the vacuum: Look at the Vacuum panel under the Setup menu. The
GUN, COLUMN and CAMERA values should look like the ones below and
highlighted in green. Gun will always be 1 Log.
4. Fill the cold-trap dewar with LN
2
: Cover the screen window first. Fill the dewar
until it is full. If you are the first user of the day, refill it again after 30 minutes.
Refill the LN
2
at least every 3 hrs to keep it full
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5. Inserting the specimen holder
Room temperature sample
There are two things to check prior to inserting the specimen holder:
(a) Under the Search tab, in the Stage
2
menu, click on the flap-out menu and click
Control then Holder. This will reset X, Y, Z, and α on the stage and avoid damaging the

Summary

Startup Procedures

Check Microscope Vacuum

Verify vacuum status in the setup menu, ensuring specific values are green.

Fill Cold-Trap Dewar with LN2

Procedure for filling the LN2 dewar and its refill frequency.

Specimen Holder Insertion

Room Temperature Sample Insertion

Steps for inserting a room temperature sample holder.

Cryo Sample Insertion

Steps for inserting a cryo sample holder.

Specimen Holder Removal

Microscope Alignments

Eucentric Height Adjustment

Adjusting Z height to minimize image displacement during eucentric height adjustment.

Condenser Aperture Centering

Center the beam using trackball and position knobs at ~10,000x magnification.

Condenser Lens Stigmation

Obtain a triangular crossover beam using X and Y stigmator knobs at 135,000x.

Direct Alignments

Beam Shift Alignment

Center the beam in the middle of the phosphor screen using Multifunction knobs X and Y.

Beam-Tilt Pivot Points

Minimize beam movement by adjusting pivot points X and Y at crossover.

Rotation Center Alignment

Minimize displacement of an identifiable object using MF X and Y.

Comma Free Alignment

Correct alignment using live FFT to show zeros at same frequencies.

Objective Aperture and Stigmation

Objective Aperture Centering

Center aperture around the un-diffracted beam at 50,000x.

Objective Lens Stigmation

Make objective lens stigmation rings circular using MF X and Y knobs.

STEM Mode Operation

Procedure Finishing

Using the Falcon II Detector

Overview

1. Function Description
2. Important Technical Specifications
3. Usage Features
4. Startup and Software
5. Vacuum System
6. Cold Trap Maintenance
7. Specimen Insertion (Room Temperature Sample)
8. Specimen Insertion (Cryo Sample)
9. Microscope Alignments
10. STEM Mode Operation
11. Falcon II Detector Usage
12. Maintenance Features
13. Specimen Holder Removal
14. Shutdown Procedures

This document outlines the operating procedures for the FEI Tecnai G² F20 microscope, covering startup, specimen handling, microscope alignments, STEM mode operation, and shutdown, along with specific settings for using the Falcon II detector.

Function Description

The FEI Tecnai G² F20 is a high-resolution transmission electron microscope (TEM) designed for advanced materials science and biological imaging. It supports various imaging modes, including standard TEM and Scanning Transmission Electron Microscopy (STEM), and is equipped with a Falcon II detector for high-performance imaging. The microscope allows for precise control over electron beam parameters, specimen positioning, and image acquisition, making it suitable for detailed structural and compositional analysis at the nanoscale.

Important Technical Specifications

The microscope boasts a line resolution of 0.144 nm, indicating its capability to resolve extremely fine details. It features a Cs objective of 2.0 mm and a Cc objective of 2.0 mm, which are critical parameters influencing image quality and aberration correction. The focal length is 2.7 mm. The primary detector specified is the FEI Falcon II, which has a physical pixel size of 14 µm. These specifications highlight the microscope's ability to achieve high-resolution imaging with good contrast and signal-to-noise ratio.

Usage Features

Startup and Software:

The startup sequence involves launching the Tecnai User Interface, Digital Micrograph, and TIA (TEM Imaging and Analysis) software in a specific order. This ensures all necessary control and imaging functionalities are active.

Vacuum System:

A critical startup step is checking the vacuum status. The system provides real-time feedback on GUN, COLUMN, and CAMERA vacuum levels, which should be highlighted in green, with the Gun always at 1 Log. This ensures optimal operating conditions and prevents damage to the electron optics.

Cold Trap Maintenance:

The cold trap dewar must be filled with liquid nitrogen (LN2) at startup and refilled every 3 hours to maintain a high vacuum and protect the column from contamination. An initial refill after 30 minutes is recommended for the first user of the day.

Specimen Insertion (Room Temperature Sample):

Before inserting a specimen, the objective aperture must be removed, and the stage reset using the "Control then Holder" function under the Search tab to prevent damage. The specimen holder is inserted carefully, rotated clockwise to its final pumping position, and then slowly slid into the microscope after the red Compustage light turns off and the turbo pump reaches operating speed. The system provides a countdown in the Vacuum Overview window.

Specimen Insertion (Cryo Sample):

For cryo samples, the procedure is similar but includes additional steps for tilting the stage to -55 degrees using "Search>Stage²>alpha toggle" and prepumping the airlock via "Setup>Vacuum>Cryo" before insertion. After insertion, the stage is reset to 0 degrees, the turbo is switched off, and the liquid nitrogen in the holder is topped up.

Microscope Alignments:

• Eucentric Height Adjustment: This involves opening column valves, finding a feature at 4000-5000x, activating the alpha-wobbler, and adjusting Z height to minimize image displacement, followed by pressing "Eucentric Focus."
• Condenser Aperture Centering: A C2 aperture (100um) is selected, and at 10,000x, the beam is centered at crossover using the left trackball and then expanded to ensure concentricity.
• Condenser Lens Stigmation: At 135,000x, the beam is brought to crossover, and the "Stigmator" panel under the Tune menu is used to adjust multifunction knobs X and Y to achieve a triangular crossover beam.
• Direct Alignments: Performed at 50,000x and close to focus, these include:
  • Beam Shift Alignment: Centering the beam at crossover using multifunction knobs X and Y.
  • Beam-Tilt Pivot Points (X and Y): Minimizing beam movement at crossover using multifunction knobs X and Y to achieve a single bright point.
  • Rotation Center Alignment: Minimizing displacement of an identifiable object using MF X and Y.
  • Comma Free Alignment: Using the Orius CCD at slight underfocus (-500 nm) and live FFT to correct comma aberrations, ensuring alternating power spectra show zeros at the same frequencies.
• Objective Aperture Centering: At 50,000x, the diffraction button is pressed, the objective aperture is inserted, and centered around the un-diffracted beam using aperture position knobs.
• Objective Lens Stigmation: At 50,000x, with the Orius CCD active and slight underfocus on carbon support, a live FFT is used to observe Thon rings. The "Stigmator" panel under the Tune menu is used to adjust MF X and Y knobs to make the rings circular, correcting astigmatism.

STEM Mode Operation:

This mode involves finding an area of interest at low magnification (~10 k), activating STEM mode, deactivating diffraction mode, performing specific Direct Alignments (Beam Shift, Beam-Tilt Pivot Points X/Y, Rotation Center, Condenser astigmatism), re-entering diffraction mode, inserting the STEM detector, choosing a camera length (100-150 mm for LM STEM) and spot size, and then using "Search" or "Preview" to view and "Focus" to adjust the image. "Acquire" obtains the image, which can then be saved via "Export Data" in TIA.

Falcon II Detector Usage:

For optimal imaging with the Falcon II detector, all microscope alignments should be performed outside of Low Dose mode. TIA must be open, and a specific low dose file (50K_recommended.lds) should be loaded, or custom settings applied. Recommended settings include:

• Search: 1,700x (Orius), C2 aperture 100, Spot size 9, Defocus -200 µm, Dose Rate <0.02 e-/Ų/sec.
• Focus: 150,000x (Orius), C2 aperture 100, Spot size 6, Defocus 0-4 µm.
• Exposure (2 sec integration time): 50,000x (Falcon), C2 aperture 100, Spot size 6, 10 e-/Ų/sec (2.7 sec). At 50,000x, the pixel size is 2.08Å.

Maintenance Features

Specimen Holder Removal:

The removal process involves resetting the stage ("Search>Stage²>Reset Holder"), closing column valves ("Setup>Vacuum>Column Valves"), and then carefully retracting the holder by pushing against the purple plate of the stage, rotating it clockwise ~120°, and pulling it out gently and parallel to the stage axis, overcoming the vacuum pull.

Shutdown Procedures:

The finishing steps include closing column valves, resetting the specimen holder position, removing the specimen, retracting apertures, and checking the web scheduler. If the last user, the LN2 dewar must be removed, a paper towel placed on the dewar stand, and the "Cryo Cycle" initiated from the Vacuum panel under the Setup menu (this process takes 4 hours to complete).

FEI Tecnai G2 F20 Specifications