FEI Tecnai G 2 F20 Operating Procedures

Transcription

1 FEI Tecnai G 2 F20 Operating Procedures 1. Startup (1) Sign-up in the microscope log-sheet. Please ensure you have written an account number for billing. (2) Log in to the computer: Login to your account using your username and password. (3) Startup the software: Start the software in this sequence: 1 st : Tecnai User Interface 2 nd : Filter Control 3 rd : Digital Micrograph (Note: If Digital Micrograph cannot find the CCD Camera, close Digital Micrograph and Filter Control and restart them again in the same sequence). 4 th : INCA (Note: Once INCA has initialized, go to Options>Detector Control and click on Open for the shutter. 5 th : TIA (TEM Imaging and Analysis) (Note: Once TIA has initialized go to INCA and under Options>Detector Control and click on Closed for the shutter. (4) Check the vacuum: Look at the Vacuum panel under the Setup menu (Fig. 1) The GUN, COLUMN and CAMERA values should look like the ones below and highlighted in green. Column vacuum may be around 11 Log and may only reach 6 Log after liquid nitrogen has been added to the cold-trap. (Check also Vacuum Overview in the menu selection) Figure 1. 1

2 (5) 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 20 minutes. Refill the LN 2 at least every 3 hrs to keep it full. (6) Load an Alignment file: Under the Tune menu go to the Alignments, click on the flap-out menu and click on File. Select the file that corresponds to the account (e.g. for the user account select the user: file). This will show the type of alignments Selected and Available. Double-click all alignments in the Available section to move them to the selected section. Finally click on Apply. 2. Specimen Loading and Unloading (1) Specimen holder removal (for single and double-tilt holders) (refer to Fig. 2) (a) Ensure the column valves are closed (under the Setup menu); (b) Under the Search menu Stage 2, click on the flap-out menu and click Control then Holder. This will reset X, Y, Z, α and β on the stage and avoid damaging the double-tilt holder. Wait until the red light on the Compustage is off before proceeding; (c) For double-tilt holder, disconnect the cable plug (the Compustage red light will come on); (d) Pull the holder as far out of the CompuStage as it will go, then rotate it clockwise as far as it will go (about 120 degrees); (e) Carefully extract the holder from the airlock (you will have to pull against the vacuum), keep the holder center aligned during the removal and avoid scratching the channel inner wall; (f) Place the holder on its stand for specimen exchange. Figure 2. 2

3 (2) Loading specimen onto the double-tilt holder (a) The double-tilt holder should be placed in the stand when not in the microscope and the tip protector should be on unless a specimen is being changed. (b) Place the specimen first, covered by the washer and then the hex-ring. Please be careful not to loose the hex-ring and washer (very expensive and we only have one). Exercise very gently, as the pivot points of the double-tilt are weak. (3) Specimen holder Insertion: (refer to Fig. 3) (a) Align the specimen holder with the airlock trigger pin parallel to the small slit in the CompuStage front plate (at roughly four o'clock). Carefully insert the end of the specimen holder into the airlock cylinder and gently slide the holder in until a stop is reached. At this point the prepumping of the airlock will start as indicated by the red CompuStage light which will be illuminated. If the light does not come on, the trigger has not been positioned correctly. Slowly turn the holder slightly to the left and the right until it will go in a bit further (the airlock trigger pin now falls properly into its groove). (b) The microscope will ask you for the type of specimen holder inserted. Select the type of holder from the drop-down menu and click the ENTER button. If you entered the double-tilt holder it will then ask you to connect the cable. Connect it and click ENTER. You can look at the progress of the vacuum and airlock status by selecting Vacuum Overview in the menu selection. (c) When the red CompuStage light has switched off, rotate the specimen about 120 degrees counter-clockwise as far as it will, then allow it slide in further slowly into the microscope. Once loaded, turn off the turbo pump by clicking on Turbo On. If using the single or double-tilt holders, replace the conical stage cover to reduce drift and increase stage stability. 3

4 For Beginners For Advanced Users Figure 3 3. Microscope Alignments (1) Choose the extraction voltage For biological applications, Cryo-TEM and low-dose, 3950 is a good choice so as to reduce beam damage. For regular non beam-sensitive samples is suggested. For EDS applications and STEM, 4500 has been optimally aligned for this purpose. You can recall a Gun-setting under the Gun menu in the FEG Registers panel (Fig 4) by selecting a setting and clicking on Set. This will set the extraction voltage for that value and recall the gun alignments. It will also automatically set a gun-length and spot size that can be changed if required. (Do not click on update, delete, or Add!). Load the most current file from C:\Feg Registers\. Figure 4 4

5 (2) Eucentric height adjustment (a) Open the column valves under the Setup menu. The beam will move slowly into the center of the phosphor screen. At a magnification of about x, find a noticeable feature on your specimen. (b) Press on L2 on the left-hand control panel to activate the alpha-wobbler tilting. Change the Z height on the right-hand control panel to minimize the image displacement. (c) Press L2 again to stop the wobbler. Press on Eucentric Focus on the right-hand control panel. (3) Direct Alignments: Under the Tune menu go to Direct Alignments (Figure 5) Figure 5 Perform direct alignments at ~20,000X (a) Beam Shift alignment: Click on Beam Shift and go to crossover. Center the beam in the middle of the phosphor screen using Multifunction knobs X and Y. (b) Beam-Tilt Pivot Points (X and Y): Click on Beam-Tilt Pivot Points X and go to crossover. Try to minimize the movement of the beam using Multifunction knobs X and Y. Ideally the beam should look like the picture below with a single bright point and minimum movement. If beam moves away from center redo Beam-shift alignment. Repeat the same procedure for Beam-Tilt Pivot Points Y. Bad Good Figure 6 5

6 (c) Rotation Center alignment: Find an identifiable object in your specimen at ~20 k x. Click on Rotation Center and minimize its displacement using MF X and Y. Once you have performed the Direct Alignments click on Done to exit. (4) Condenser lens stigmation: (Fig. 7) Go to a magnification of ~150,000X and go to crossover. Under the Gun menu click go to Stigmator and click on Condenser. Use multifunction knobs X and Y to obtain a triangular crossover beam. Once done click on None to exit. Figure 7 (5) Centering the condenser and objective apertures. Condenser: (a) At a magnification of ~10,000, go to crossover and center the beam using MF XY or the trackball. (b) Expand the beam and make sure its expands concentrically. If not center it using the condenser aperture position knobs. Objective: (a) Remove the objective aperture by sliding it to the right (appendix). (b) At a magnification of about 40000x (TEM Mode) press the diffraction button on the right control panel. Insert the objective aperture in (slide left) and using the aperture position knobs on the aperture center it around the center of the beam. (c) You may switch to a different aperture by rotating the aperture selection knob (appendix table). Try not to touch the outermost knob! (6) Objective lens stigmation: (a) Under the EFTEM menu click on EFTEM for the EFTEM mode, or unclick it for the TEM mode. Load correct magnification table for the EFTEM or TEM; (b) Choose appropriate magnification (~300 kx). Adjust the diameter of the beam to approximately 15 mm (3X the size of the smallest circle on the phosphorus screen).press R1 to lift the screen; (c) In DM click go to the Camera Acquire menu on the left and click on Start View to get a live image of your specimen. Adjust the exposure time to between

7 seconds to obtain higher signal images. Under the Process menu select Live FFT to obtain a live FFT of your image. (d) In the Stigmator Tab select the Objective, correct the objective astigmatism using the MF X and Y. (e) Select None in the Stigmator when the stigmation is done. 4. Data Recording (1) Using the GIF-CCD: The Tecnai microscope is equipped with a 2k 2k CCD camera. The camera can be controlled either by the GATAN DM or FEI software TIA (Tecnai Image and Analysis). What you use is up to your personal preference. CAUTION: Do not over-saturate the CCD camera. Check that you are in or below the GREEN saturation area in the intensity panel in Digital Micrograph. Method A: CCD recording using Digital Micrograph (recommended): (a) Under the EFTEM menu go to the CCD/TV Camera panel. Set Controller to GATAN CCD and leave camera to GIF CCD (Fig. 8). (b) In DM go to Microscope> Mag table> Load and choose the correct magnification table for TEM (TEM.gts.gtg) or EFTEM mode (EFTEM.gtg). These 2 files are located under C:\Magnification Calibration\ (c) Condense the beam to approximately 15 mm (3X the size of the smallest ring on the screen) and then press R1 on the right-hand control panel to lift the screen. (d) In DM click go to the Camera Acquire menu on the left and click on Start View to get a live image of your specimen. Adjust the exposure time to between seconds to obtain higher signal images. (e) To acquire an image go to the Camera Acquire menu and set an exposure time in seconds (usually 1-2 sec). To acquire an image click on Start Acquire. Method B: CCD recording using TIA (only calibrated in the EFTEM mode): (a) Under the EFTEM menu go to the CCD/TV Camera panel. Set Controller to TIA CCD and leave camera to GIF CCD (Fig. 8). (b) Under the EFTEM menu click on EFTEM. Condense the beam to approximately 40 mm (the size of the second smallest ring on the screen) and then click on R1 on the right-hand control panel (to lift the screen). (c) Click on Search in the CCD/TV Camera panel to start viewing a live image of your specimen. You may also check the objective astigmatism by viewing a live FFT in search mode. (d) To record a full-quality (2Kx2K) image click on Acquire. You can change the exposure time and image size in the flap-out menu panel and going to Settings. of the CCD/TV Camera 7

8 Figure 8 (2) Using the plate camera: The plate camera holds up to 56 negatives. (a) Under Camera make sure exposure time is set on Auto so that the exposure time is adjusted depending on the beam brightness (Figure 9). You may also enter text that you would like to appear on the exposure. The inner most part of the elbow shape markings on the phosphor screen mark the area that will be exposed. (b) To expose a negative press on the Exposure button on the left-hand control panel. Figure 9 5. STEM mode (a) Find an area of interest at a low magnification (~10 k); (b) In the STEM/EDX menu click STEM, the Diffraction mode will be activated; press the Diffraction button to deactivate the Diffraction mode; (c) Under the Direct Alignments, perform Beam Shift, Beam-Tilt Pivot Points X/Y, and Rotation Center (turn the outer ring of the objective focus know counter-clock wise to stop the wobbling), correct the Condenser astigmatism (triangular shape); (e) Press the Diffraction button to return back to the Diffraction mode; (f) Insert the HAADF detector by clicking ins. HAADF; 8

9 (g) Choose a proper camera length (~ mm for LM STEM) and spot size; (h) Click Search or Preview to view the image, and click Focus and move the red box to a contrasty area to adjust focus using the objective focus knob; (i) Click Acquire to obtain an image. In the TIA analysis mode, select the image or panel and save them by right-clicking and choosing Export Data. 6. Collection of EDS (1) EDS spectrum in the TEM mode (a) Inserting the EDS detector manually; (b) Select STEM/EDX menu, choose appropriate Beam Settings (normally in Nanoprobe mode with spot size over 6); illuminate the area of interest with the electron beam; Note: higher spot size number, smaller actual beam prob. (c) Open the shutter; (d) Select EDX panel and click Search; (e) Check the dead time and adjust it to % by controlling the intensity; (f) Collect EDS after clicking on Acquire; (g) Use the elemental table to identify peaks; (h) Right-click on the spectrum to save the data. (2) EDS spectrum in the STEM mode (a) Go to STEM mode and find a spot of interest; (b) Move the + to the spot; (c) Follow the procedures above for the EDS spectrum collection in the TEM mode. (3) Line Scan (a) Go to STEM mode and find an area of interest; (b) Go to Experiments menu, select SpectrumCollection from the Select component dropdown menu, and choose Spectrum profile or Drift corrected spectrum profile (c) Designate the box to a contrasty area (for the drift correction) and set the line to the area of interest; (d) Set up the collecting time at each pixel and the drift correction; (e) Click on Acquire; (f) After collection, go to TIA analysis mode and save the results as.emi format; (g) Identify proper elements from the periodic table; find AutoMap, click Setup and select Display profiles in single display; (h) Click on Generate Output to generate the line scan results. Save them by right clicking the objects. (3) EDS Mapping (a) Go to STEM mode and find an area of interest; (b) Go to Experiments menu, select SpectrumCollection from the Select component dropdown menu, and choose Imaging or Drift corrected imaging; (c) Designate a box to a contrasty area and select another box to the area of interest; 9

10 (d) Set up the collecting time at each pixel and the drift correction; (e) Click on Acquire; (f) After collection, go to TIA analysis mode and save the results as.emi format; (g) Identify proper elements from the periodic table; find AutoMap, click Setup and select Display profiles in single display; (h) Click on Generate Output to generate the line scan results. Save them by right clicking the objects. 7. PEELS (a) Select EFTEM menu and click Spectroscopy; (b) Illuminate the area of interest with the electron beam, choose appropriate Beam Settings (normally in Nanoprobe mode with spot size over 6), and then press Enter; (c) Choose appropriate entrance aperture (normally smaller one, 1 mm) from the AutoFilter panel; (d) Collect the zero loss spectrum and measure the energy shift; (e) Input the energy shift and click Align ZLP for the zero loss peak alignment; (f) Click on Search to view the spectrum, and click Acquire and save the spectrum. 8. EFTEM (a) Under the EFTEM menu click on EFTEM, and ensure to load correct magnification table for the EFTEM; (b) Click Filtered; (c) Choose appropriate entrance aperture (normally large one, 5 mm) from the AutoFilter panel (d) Click Align ZLP to for the zero loss peak alignment; (e) Click Custom and then El. Map, input the elements for the mapping followed by the exposure time; (f) Save the results. 9. Finishing (a) Close the column valves (under the Setup menu, Fig. 1); (b) Set the extraction voltage to 4100 under Gun menu; (c) Reset the specimen holder position, take it out from the microscope, remove your specimen from the holder, and re-insert the holder back; (d) Retract the objective and diffraction apertures; retract the EDS detector; put the phosphor screen down; cover the viewing window; (e) Check the web scheduler. If you are the last user for the day, remove the LN 2 dewar, place a paper towel on the dewar stand and immediately go to the Vacuum panel under the Setup menu (Fig. 1), click flap-out menu Cycle (it takes 6 hrs to complete the process);, in the Cryo tab click Cryo 10

11 (f) Transfer your data in time. The computer is not intended for long-time data storage and is purged periodically; (g) Finish the instrument time sheet. Report to the microscope staff for any problems you experienced. 11

12 Cautions You may be able to restart programs after asking the microscope staff when malfunctioning but YOU ARE NOT ALLOWED TO RESTART THE COMPUTER FOR ANY REASON! When you restart programs follow the sequence of opening. (User Interface Gatan Filter Control Digital Micrograph Inca (and open the shutter of the EDS detector) TIA) Do not click on High Tension and Operation at the Set-up menu. (They should be kept activated (highlighted in yellow). If you find they are not activated ask the microscope staff. When tilting to a high angle, be careful and slow down from ± 50 degree even when the stage is at the eucentric position. (Check the current angle in the right bottom panel of the left monitor always.) Keep the EDS detector out with the shutter closed when you are not using EDS. Do not focus intensive beam on the phosphor screen for long time, and put down the phosphor when you are not using the GATAN CCD camera. Do not change the program settings! 12

13 Appendix: Apertures Aperture diameter (µm) Aperture No Condenser Condenser Objective Selected Area

14 Tecnai G 2 F20 Specifications 14

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