FEI Tecnai G2 F20
Transmission
Electron Microscope
User’s Quick Reference Guide
ContentsPage
Overview3
Staff Contact Information4
Emergency shut down procedures
5
Acronyms and abbreviations7
Introduction8
Starting a session10
Overview of the F20 Hardware
11
Viewing screen and binoculars
15
Cold trap (anticontaminator device, ACD)
16
Control Panels17
Overview of the Tecnai software
18
FEI Logic20
HT and Emitter / Gun settings
22
Preparing to load a sample
23
Loading the sample holder into the microscope
24
Removing the sample holder
28
Driving around30
Finding the beam31
Simple alignment procedure for CTEM
32
Saved alignments36
Tecnai Stigmator controls38
Compustage Alpha and Beta tilt controls
39
Alpha and Beta tilt limitations using objective apt.
40
Tecnai automated apertures41
Recording CCD images and diffraction patterns
44
Using the Bruker X-Ray analysis system - TEM -
45
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ContentsPage
Operating in STEM mode
46
Gun alignment for high resolution STEM
49
STEM Gun Lens and Probe formation
51
STEM detectors52
Convergence and Collection angles
53
Saving and transferring data54
Ending a session55
ACD Cryocycle56
Vacuum and HT Problems
57
Tecnai F20 Quick reference guide
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Overview
This guide describes the basic procedures for operating the FEI Tecnai G2 F20 transmission
electron microscope in imaging, diffraction and microanalysis (EDS) modes. It is intended
as a quick reference for users who have been trained and licensed to operate this microscope
at MCEM as well as new trainees. It is neither a training document nor a textbook on TEM.
In addition, it is not meant to replace the detailed notes trainees are strongly encouraged to
take. Instead, this manual is intended as a checklist of the procedures to follow in order to
operate the microscope safely (for you and for the microscope).
If you are in any doubt about the operating procedures described in this document please
contact one of the MCEM staff members listed below before continuing.
Unless you are a trained Tecnai F20 user with at least a business hours licence, do not operate
this equipment without supervision. Your licence (listed on the laboratory door) will allow
you to operate the instrument during certain times only, please be sure that you do not operate
this or any other equipment out of your licenced hours. If in doubt, please ask. Supervised
users and trainees must seek assistance before beginning and ending their sessions and at any
times that samples are exchanged.
MCEM Staff Member contact information for TEM users:
Dr. Tim Williams
Dr. Russell King
Room 103
Room G34
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Telephone 20721
Telephone 53804
(Microscope manager)
(Microscope Engineer)
EMERGENCY SHUT DOWN PROCEDURE FOR TECNAI F20
1. In the event of a fire alarm evacuation, DO NOT shut down the microscope but just leave
the room
2. IN THE EVENT OF ANY EMERGENCY IN THE MICROSCOPE ROOM, YOUR
PRIMARY OBJECTIVE IS TO LEAVE THE AREA SAFELY
3. ONLY if time and your personal safety permit, carry out the following microscope shut
down procedure
4. Press the RED OFF button on the SOOP panel to the right of the viewing screen. Do Not
turn down HT, remove the sample or any other normal steps
5. Leave the room.
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6. Switch OFF the chiller unit in the F20 utilities room G16 by pressing the black switch on
the front panel
7. Contact one of the MCEM staff members on the list below
8. Contact Monash Security by calling 333 on any Monash phone but do not remain in the
F20 lab. G17 or utilities room G16.
MCEM Staff Member contact information for TEM users:
Dr. Tim Williams
Dr. Russell King
Mr. Renji Pan
Room 103
Room G34
Room G34
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Telephone 20721
Telephone 53804
Telephone 54931
(Microscope manager)
(Microscope Engineer)
(Microscope Engineer)
Acronyms and Abbreviations
AH
After hours microscope licence
BH
Business hours microscope licence
SU
Supervised User license
DM
Gatan Digital Micrograph, CCD camera software
TIA
Tecnai Imaging and Analysis, CCD camera software
UI
User interface (Tecnai)
HT
High Tension, another way of saying accelerating voltage
OL Objective Lens (the Tecnai F20 “Twin” lens)
CL
Condenser lens (generally condenser lens 2 or C2)
CP
Control panel in software, e.g. Direct Alignments CP
LH CP
Left hand control panel for the Tecnai
RH CP
Right hand control panel for the Tecnai
SOOP
Tecnai’s Switch-On-Off-Panel (4 lit push buttons)
LN2
Liquid nitrogen
Col
Column (of the Tecnai)
ACD Anti Contamination Device, a LN2 cooled cold finger
Cryo Cycle Cryogenic cycle; in this case it refers to the Tecnai ACD warming and
Turbo-pumping cycle carried out overnight or after the last session
CCD Charge coupled device (camera), the Orius SC200D and SC600 are fitted to the F20
HT
High Tension = Accelerating Voltage
FEG
Field Emission Gun
FEG REG
FEG registers
STEM
Scanning Transmission Electron Microscopy
HAADF
High Angle Annular Dark Field
BF/DF
Bright Field / Dark Field (detector, for STEM)
EDS
Energy Dispersive Spectrometer
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Introduction
The FEI Tecnai G2 F20 field-emission gun transmission electron microscope (FEG-TEM)
is intended for conventional imaging (CTEM), scanning transmission (STEM), diffraction
and microanalysis (EDS) work on a very wide range of materials science problems ranging
from nanomaterials, metal alloys, polymers to ceramics and minerals. It operates at 200 kV
accelerating voltage (as well as any intermediate voltage from 20 kV as required) and is
equipped with a thermal (Schottky) field-emission gun. The microscope objective lens is
the FEI Tecnai “Super Twin” lens type and the spherical aberration coefficient Cs = 1.2 mm
permits a CTEM point resolution of 2.4 Å.
The five axis “Compustage” goniometer allows for fully computer-driven electronic stage
translate (x-y-z) and tilt in two orthogonal axes (A, B) as well as storage and recovery of
any stage position during a session. The A tilt range is +/- 35 ° and with the double-tilting
sample holder and low background, double-tilting analytical sample holder the B tilt range
is +/- 25 °. As well as single tilting and double tilting holders, there is also a three sample
single-tilting specimen holder that allows any of the three loaded positions (grids, foils, FIB
samples etc.) to be examined without reloading the sample holder.
The F20 is equipped with a gun isolation valve and the specimen holder can be inserted and
removed with the high tension on, making for extremely rapid turnaround times. During
normal business hours the microscope remains “on” at all times and each user will only be
concerned with specimen exchange and alignment before starting work.
Two retractable CCD cameras are fitted to the F20. The Gatan Orius SC200D camera located
above the viewing chamber is a 4K (2048 x 2048) pixel cooled CCD, lens coupled to the
scintillator. Special design allows this CCD camera to be used to record both images and
diffraction patterns (inlcuding selected area / spot patterns) without “blooming” or CCD
damage. The SC200D can also record high quality images. Below the viewing chamber,
the second CCD camera is a Gatan Ultrascan 1000 4K (2048 x 2048) pixel cooled CCD
that is used for high resolution image acquisition (no diffraction work). Both CCD systems
may be operated either through the native FEI Tecnai “TIA” interface or by Gatan “Digital
Micrograph” at the option of the user.
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Images and diffraction patterns may also be recorded on plate film using the 56 plate camera
system.
Analytical work is supported with a Bruker Silicon Drift Detector (SDD) detector operating
through the Esprit user interface. This is a windowless detector with 123 eV (Mn ka) energy
resolution. Point spectra (focussed probe) or area spectra (defocussed probe) spectra can be
recorded with this system.
The F20 is suitable for high resolution STEM with a resolution (using HAADF detector)
better than 2 Å. Both HAADF (Z-contrast) and conventional BF-DF (diffraction contrast)
detectors can be used simultaneously. STEM imaging may also be combined with the Bruker
EDS system for advanced chemical imaging and analysis.
The F20 is almost entirely operated through the PC interface using a combination of hand
controls on the two control panels and mouse / keyboard commands. Except for the hand
operated condenser, objective and selected area aperture assemblies, the specimen holder
insertion / removal and positioning the small fluorescent binocular viewing screen, all
microscope operations are controlled electronically.
Microscope alignments can be saved / restored from the PC hard disk and compared to
previous generations of TEM, the Tecnai is remarkably stable in alignment from day to day,
requiring little time to acheive good performance.
With a current alignment loaded, and if you take care to always focus your sample using
the Compustage Z (height) control at the Eucentric Focus objective lens setting, rather than
simply turning the “Focus” knob (......) you will be rewarded with faster and better alignment,
probably without having to make other than tiny adjustments to the pivot points, current
centre and object lens astigmatism. If the crystal is aligned on an appropriate zone axis you
will get good lattice fringes / lattice images without heroic efforts.
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Starting a session
User operations are relatively simple and essentially consist of:
1. Loading the sample holder with your specimen using the hutch and light microscope
2. Plasma cleaning the sample + holder
3. Loading the holder into the TEM
4. Opening the column isolation valves
5. Simple alignment checks / loading a stored alignment file, FEG registers etc., as required
6. Operating in TEM, STEM, diffraction, EDS modes as required
7. Closing the column isolation valves
8. Removing the holder and sample
9. Saving CCD images to the networked N drive
10. Filling in the log book and tidying up the lab.
Occasionally (typically, midday and late afternoon), business hours users will also be
required to top up the liquid nitrogen in the anticontaminator dewar and if the last user of the
day, start the ACD cryocycle. See below for details.
The high tension remains at 200 kV at all times unless it is specifically required to be set at
another voltage. Please see MCEM staff to have the accelerating voltage changed.
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Overview of the F20 hardware
This is the F20 installation at MCEM. In addition, the separate utilities room houses the F20
water chiller and some electronics cabinets.
The microscope utilties are monitored by software and it is only required for users to note
the water temperature (19 °C), water flow (nominal), high and low pressure N2 pressures
(nominal) and log these as “OK” or otherwise.
Seated at the console there are three LCD monitors: two (L, C) for TEM operation and one
(R) for EDS and file copying etc. You will notice the two control panels to L and R of the
column, these are the LH CP and RH CP, used for common operations such as changing
brightness, magnification, moving the stage, etc.
The column has 4 automated aperture assemblies: from top to bottom the Condenser 1,
Condenser 2, Objective and Selected Area apertures. Each has four positions except OA,
which has 8: 4 (8) is largest and 1 smallest. The sizes are listed elsewhere in the Guide.
Except for the Condenser aperturers where one is always selected, the OA and SA apertures
can be pre-selected and then moved in and out of the beam. Aperture alignment is done by
adjusting the two multifunction knobs.
See the three large images below for location of the main Tecnai components.
Tecnai F20 Quick reference guide
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Gun
Column
Goniometer
Utilities rack
Main
display
Viewing
screen
LH
panel
RH
panel
Console
Overview of the F20 main hardware items - front view of installation
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Electronics
cabinet
HT Tank
Utilities
Rack
Vacuum
pumps
Ultrascan
controller
Rear view of the F20 main hardware items (HT, utilities, vacuum pumps, electronics).
Ultrascan 1000 CCD controller is located on top of electronics cabinet to LHS of column.
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Gun
Column
Main display
SC200D CCD
Binoculars
camera Condenser apertures
Objective apertures
Viewing
LH control
screen
panel
Selected area apertures
Front view of F20 column and
operator’s console (TOP) and
the RHS controls, including the
Switch-on-off panel (SOOP),
Scan Switch and the Gatan BFDF STEM detector pneumatic
controller box.
The Gatan detector signal box
is placed further away from the
column to the right, to minimise
electromagnetic interference.
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Goniometer
SOOP
RH control
panel
ACD dewar
Scan Switch
SOOP
RH control
panel
BF-DF
controller
Viewing Screen and Binoculars
In addition to the main viewing
screen (which can be raised for
using the bottom CCD camera),
there is a small viewing screen
for direct viewing with the
binoculars. Raise the small
screen using the lever indicated
(forward to raise, back to lower).
The binoculars swivel sideways
(with CARE !!) if you prefer to
not use them. Focus the L and R
eyepieces to suit your personal
ocular requirements.
There is a moveable pointer
to aid in focusing, marking /
obscuring the beam etc.
Turn the end CCW to loosen
/ insert and twist to move up /
down. Move pointer in /out with
the larger knurled nut. Pull out
and turn CW to remove from
beam.
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Cold trap (anticontaminator device, ACD)
These images show the ACD filling procedure. Always wear PPE when handling LN2!
1. Cover the screen, RHCP and monitor.
Pre-fill the Dewar to about 50 mm from
top, away from themicroscope
2. Carefully insert the braid and fit the
Dewar slowly
3. Top up the Dewar to the copper lug....
4. ....about 20 mm from the top is correct
5. Fit the PS cap
6. Check the level every 3 hours, topping
as required
2
4
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1
3
5
Control panels
These are the two main cotrol panels, the LHCP (top) and RHCP (bottom). The LHCP tracker
ball defaults to Beam Shift but for reasons explained below we will NOT use it. Avoid using
the tracker ball to shift the beam. Multifunction X and Y are used for beam shift by selecting
Beam Shift in Direct Alignments (see below).
LHCP
Note:
The button marked “Wobbler” is generally not used; do not press it when the alignment
guide below refers to Alpha Wobbler as a different function will be used.
RHCP
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Overview of the Tecnai Software
The Tecnai is controlled by the PC user interface and two control panels, located to the L
and R of the viewing screen (LHCP, RHCP, see above). The PC operates under Windows XP
and runs three applications for the Tecnai user interface: the Tecnai UI itself (UI), Tecnai
Imaging and Analysis (TIA), and Gatan’s Digital Micrograph (DM). The latter two are used
for acquiring CCD images and diffraction patterns from the two Gatan CCD cameras. There
is also an X-ray microanalysis system running on a separate PC and described below in the
Microanalysis chapter.
The Tecnai F20 main screen will initially look something like this, but perhaps not exactly
the same as this capture (here it in in TEM, if in STEM it will differ in some details).
•
This large dark panel is where TIA will display (it is not shown here)
•
Workset is where you select and access commonly used functions such
as Vacuum/HT, Stage, CCD, Alignment
•
Available controls open as panels under the clicked Workset tab
•
Some panels have a “Flapout”, accessed by a > button on the top RH of
each menu bar
•
The bottom LH corner shows the control panel bindings for the L and R
buttons, multifunction knobs, etc.
•
The bottom panel displays current microscope settings such as
magnification, HT, spot size, focus, and Compustage XYZ, AB
positions
•
You can also access all UI functions here
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In addition to the commands available on the Workset control panels, all the available UI
commands are accessible by clicking up a list from the bottom RH corner of the UI:
Click on the dropdown arrow to show the
function list and then select with another
mouse click. The control panel will open up
above the selection window and look exactly
the same as those in the limited selection
under the Workset menus.
Here, Stigmator has been selected and the
Objective Stigmators are active.
Click None or X to make the CP go away.
In fact, any available control panel can be
allocated to any Workset menu; the Workset
menu tabs can be added to, removed, renamed
etc., but with a multi-user instrument this is
specifically not permitted as chaos would
ensue!
Not all of the IU control panels are available under the USER license login and of the many
Tecnai CP’s only those that are used routinely are covered in this Guide, each in the relevant
section.
Note: on screen Help is available for ANY UI window (every CP) by simply clicking the
mouse once in any pale yellow window area and then pressing F1 on the keyboard. A detailed
Help window will pop up, explaining the chosen window in detail.
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FEI Logic
The operation of FEI microscope buttons, both hardware and software, can be very confusing.
Fortunately, it is also very logical.
Hardware buttons
There are 4 light up hardware buttons for the Tecnai on the
SOOP (switch on-off panel) located to the RHS of the viewing
chamber. These buttons are LIT when they can be pressed to
do something.
Unlit (do nothing)
Lit (can be pressed for OFF)
In general use, none of the four SOOP buttons should be pressed. They are for engineer’s use
only except in emergencies.
In case an EMERGENCY shutdown is required, the lit RED button, Microscope Off, can
be pressed. In normal operation, the four SOOP button states are Green (off) Red (on) and
White, White (on). The two white buttons are Vacuum and HT interlocks.
The white SOOP buttons, Vacuum and HT, are lit (white) when their function is “True”, i.e.
Vacuum is “true” = ready and HT “true” = ready to switch on by software OR already on at
200 kV.
There is one other (unlit) button; the Screen Lift button on the LHS of the viewing chamber.
This simply raises or lowers the main fluorescent screen when pressed, allowing operation
of the Gatan Orius 600 CCD camera.
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Software buttons
Generally, a Tecnai user will press software
buttons, for example the Column Valves Closed or
Filament buttons. These buttons may be Yellow or
Grey when pressed. Generally, pressing a button
changes its colour, i.e. Grey -> Yellow or Yellow
-> Grey. The Turbo On button is slightly different,
because if it is Grey (turbo off), and then pressed,
it will go Orange (turbo is spooling up) before
becoming Yellow.
TRUE
FALSE
(valves closed) (Turbo off, Camera not Air)
The button words are logically “True” when the button is lit and “False” when Grey. For
example, Turbo On = Yellow means “the Turbo is on” and Turbo On = Grey means “the
Turbo is off”. For the column valves, the button Column Valves Closed = Yellow means the
valves are closed (you can’t operate the microscope); pressing it will OPEN the valves and
then Column Valves Closed = Grey, i.e. the statement is now False.
Also, the button text may be “greyed out”, in which case the button cannot be pressed,
regardless of whether it is Grey or Yellow overall. Both Yellow state (true) and Grey state
(false) buttons may be “greyed out”.
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HT and Emitter / Gun settings
The Tecnai F20 high tension and the emitter (FEG) remain ON at all times. The first user of
the day fills the anticontaminator (dewar) and the last user initiates the ACD cryo cycle (see
separate section). HT on / off (ramping) is done by MCEM centre staff only for maintenance
purposes. Never attempt to switch off the FEG or HT!
The FEG operational settings can be changed by the user, depending on whether C-TEM
or STEM work is to be carried out. There are effectively two FEG settings, set by the FEG
Register values. Selecting and setting the STEM FEG register will also switch the F20
into STEM automatically. Respective column alignments are also stored and restored from
memory, so switching TEM-STEM is relatively easy and fast. The FEG register is covered
in detail in the STEM section.
First user LN2 fill (may also be done by MCEM staff)
Using PPE provided, obtain a 2 l dewar of LN2. On the
bench, fill the Tecnai anti-contaminator cold trap dewar
with LN2 so it is about 7 cm less than full. Ensuring that
the rubber viewing screen cover and the plastic sheet
protecting monitors and RH CP are in place, carefully
insert the ACD copper braid into the LN2 and place the
dewar on the support. Top up the dewar. Fit the PS dewar
cap. Whilst waiting for the ACD to cool (~10 minutes)
prepare your sample for loading.
Note: If the emission reading is ~0 uA, the HT is off and you must seek help, because
the HT must be restarted by MCEM staff.
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Preparing to load a sample
Wearing new Nitrile gloves, prepare your sample for loading or seek help to have this done
for you if you require a different holder or other assistance. Separate instructions are available
for the three F20 Compustage holders. Refer to these during loading. You MUST be trained
for each holder that you intend to use. If you have not been trained DO NOT use it.
VERY carefully check / clean the holder
o-ring using the microscope. Even a small
fibre can cause a large leak and often cannot
be seen by eye. Remove fibres using the
bamboo stick and a clean lens tissue.
Always Plasma clean the holder (with or
without sample) before use. Most samples
may be safely cleaned: yes, even those on
holey carbon grids. See MCEM staff for
advice / training.
Before attempting to load a holder, confirm the following. Failure to ensure the correct
instrument state before holder operations can result in catastrophic damage.






Objective aperture removed and disabled (aperture menu)
Column valves closed (Yellow button)
Holder reset and X Y Z A B all reading back ~0.0. If not, select Stage2 CP and click
Reset holder
Compustage RED LED is OFF
Viewing screen covered with rubber guard
You are wearing a new pair of nitrile gloves
Now Refer to the detailed instructions below
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Loading the sample holder into the microscope
Refer to the separate section (Tecnai Holders) to load your sample into one of the three F20
holders (single tilt, low background double-tilt and standard double-tilt).
You must be wearing clean blue nitrile gloves for all sample loading operations until
the holder is fully inserted into the Compustage.
On the Tecnai UI, select the Stage CP and
click the flapout. Click Stage Reset to set
all stage translates and tilts to zero.
Confirm in the UI that XYZAB are all
zero.
On the Vacuum CP, check that Column
Valves Closed is Yellow.
Confirm that the Compustage red LED is
OFF. If it is ON, seek help and DO NOT
attempt to load the holder!
Ensure that the Objective
aperture is retracted
Using the light microscope in the
hutch, a bamboo skewer and a square
of lens tissue, inspect the holder
O-ring for hairs and other particles,
removing carefully with the clean
skewer. Finally use the N2 gas gun to
carefully blow the entire holder free of
dust.
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Insert the holder with the PIN (Arrowed)
pointing down at about a “4 O’clock”
position until it stops and then carefully
turn CW to the 5 O’clock (i.e. the white line
next to Close), at which point the holder
will go in further. You should now not be
able to turn the holder CW or push it in any
more. Confirm this by gently rotating with
your fingertips. The holder should be sitting
nicely at the “5 O’clock” position.
Pin
4 O’clock
5 O’clock
The RED LED will come on
Let go of the holder. Do not hold onto the holder as you
will certainly apply some unnecessary force.
The TURBO ON light will go ORANGE and you will
hear the TURBO backing pump and TURBO start to
spool up.
Select the correct holder type and enter return. If you are loading the double tilt holder,
connect the B tilt cable D-connector and confirm this action by clicking enter button.
The airlock will pump 4 times and purge 3 times (taking about 3 minutes)
Watch for the RED LED to go out: do not leave the room, answer calls or
become distracted!! If you miss the LED, take the holder out and restart !!
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Again, this is the
sequence:
1. Insert the holder,
pin pointing at 4
O’clock until it stops
2. Turn slightly to 5
O’clock and insert
until stops
1
3. Turbo will start up
and Red LED lights
up
4. Now wait for the
cycle to complete...
2
3-4
5
T
H
.... about a 3 minute wait....
Watch for the RED LED to go out.
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5. As soon as the red LED goes out, turn the holder 150 degrees CCW as indicated by the
white arrow towards OPEN on the purple plate and taking care to not let go of the holder
at any time, smoothly and gently insert fully- the holder black body will almost touch the
purple plate leaving only about 3mm gap.
Look at the last figure opposite: you need to turn the holder CCW until the metal tongue, T,
aligns with the hole H at the 6 O’clock position.
6. If there is a larger gap, i.e. about 10mm, still grasping the holder carefully turn it very
slightly CW< >CCW and it will then go in, as the pin on the purple plate engages the slot
on the RHS of the holder body (this is not easy to see unless you look at the “back” of the
holder). Do not let the holder drop in but always guide it in.
7. Observe the column vacuum reading: it should be
falling and close to 6. If it is not falling after a few
seconds, or if it is >20 when you look, or if it rises,
IMMEDIATELY seek help. If the column pressure is
high / rising, you may also withdraw the holder and then
turn it 150 degrees CW to close the airlock again.
8. At this stage the yellow Turbo On button may be
clicked to switch off the turbo pump; on the other hand
if you select Col. Valves Closed (to OPEN) the valves,
the software will also turn off the Turbo. Your choice.
9. If not already done, open the column valves: click the yellow Col. Valves Closed button,
and uncover the viewing chamber window. You will probably see nothing if the Mag. is still
set at 910,000 (& depending on how the Intensity setting has been left).
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Removing the sample holder
To remove the sample holder from the Compustage, the process is as follows.
1. On the Stage2 flapout, Click Reset Holder and confirm that the XYZAB have reset to
0.0. The Red LED should be OFF at this point.
2. Remove the Objective aperture and Selected Area aperture from the beam path: it is
ESSENTIAL to remove the OA in case the holder touches it during removal.
3. Close the Column Valves.
4. If you were using the Double Tilting holder, remove the B tilt connector. The Red LED
5.
6.
7.
8.
will come ON, ignore it.
Wearing a New pair of blue Nitrile gloves, grasp the holder body with your RIGHT hand
and with your LEFT hand, press the purple plate to prevent it pulling out.
Smoothly withdraw the holder until it stops, then rotate it 150° Clockwise until it stops.
At this point, you may let go of the holder and it will not move (it is back in the “5 O’
Clock” position).
Change your grip on the holder and whilst supporting the purple plate with your left
hand, carefully pull the holder straight out all the way from the airlock.
9. As the holder is withdrawn, be careful to not wave the rod about inside the airlock.
10.It is possible that the Compustage will trigger the Turbo Pump cycle as you are
removing the holder: ignore this for now. This happens because the rod touched the
internal insertion sensor (i.e. you waved it about too much).
11.Place the holder carefully in its stand in the hutch.
12.If the Turbo pump came on, let it cycle up to speed and then click to switch it off.
13.Remove your sample from the holder and check the O-ring for hairs, etc.
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1
This is the holder physical removal
sequence in pictures:
1. Supporting the Purple Plate, withdraw
holder until it stops (images 1-2)
2. Turn holder CW 150° until it stops (turning
in the Close direction shown by the white
arrow) (images 2-3)
2
3. Change your grip and carefully withdraw
fully (images 3-4)
3
4. Be careful withdraw straight and not let
the rod wave about as you do so (4-5)
5
4
Tecnai F20 Quick reference guide
March 4, 2013
• 29
Driving around
Some of the Control Panels are more often used than others. In particular, the Direct
Alignments CP is used often. Get used to opening this panel. If you wish, check Auto Help
and then every time you select a function the Tecnai Help will open. However, this will later
annoy you.
The illumination (Intensity) is controlled by the C2 lens of
the Condenser lens system, via the large Intensity knob on the
LHCP. Adjust the intensity to cover the main viewing screen.
Magnification is controlled by the middle RHCP knob, rather
mysteriously labelled Magnification. There are several
different “ranges” of magnification, related by the combinations
of lenses used.
The Focus knob on the RHCP is used at very high magnification when the sample is
approximately focussed by the Z axis (height) of the compustage (RH side of RHCP).
The black Joystick (RHCP) is
used to translate the sample in
X-Y. In addition, the sample
position can be controlled
electronically from the Stage
CP. Positions (including tilt) can
be stored and returned to at any
time with great accuracy.
Tecnai F20 Quick reference guide
March 4, 2013
• 30
Finding the beam
Set the (or
conditions:
confirm)
following
Spot size 1 (LHCP L3)
Intensity on Coarse (LHCP)
1
Magnification ~10,000 (RHCP)
Diffraction and Dark Field off (no red
light)
Condenser aperture 1 selected
No objective aperture or selected area
apertures inserted
Adjust the Intensity control CW and
CCW and once you see the beam,
spread it to cover the screen.
Use LHCP Trackerball to centre the
beam or select Direct alignments /
Beam shift.
Tecnai F20 Quick reference guide
March 4, 2013
• 31
Simple alignment procedure for conventional TEM imaging
Using the Compustage X-Y joystick
(RHCP) translate the sample until
you have a hole or empty grid square
centred. The sensitivity of the joystick
can be changed with the - + buttons
and the joystick is also position and
magnification sensitive, so moving it
more will increase the relative slew
rate. Use a low mag. setting (<10,000)
Find a recognisable feature in your sample, such as a crystal fragment or a small hole in a
foil. Press Eucentric Focus (RHCP). Always do the alignment at eucentric focus!
At a magnification of 10,000 ~ 40,000 or more if you prefer and are confident, focus the
sample using the Z (sample height) axis (RHCP).
Alpha Wobbler
Select Alpha wobbler (LHCP, L1): the
Compustage will rock + / - 15 degrees
automatically. The sample feature
will probably zoom L - R and perhaps
disappear. Nil desperandum! Just press
the Z axis upper button to raise the
stage height (+ Z value) to between 50
and 150 um and stop the motion.
As you do this, observe the movement of your chosen feature. It will slow down and eventually
stop, then reverse and move again. Using the two Z buttons, adjust the height to completely
stop the movement. The required Z adjustment will ALWAYS be + (up) about 50 ~ 100 um.
Tecnai F20 Quick reference guide
March 4, 2013
• 32
Why is this? Because your sample is loaded into the compustage sitting on top of the inner
holder recess. However, when you load the holder you rotate it 180 degress (i.e. upside down),
thus your foil or grid is then below the reference height (“eucentric focus”). Consequently,
you focus the sample by bringing it back up to eucentric.
Switch off Alpha wobbler (press L1) and increase the magnification to a higher value
(anything up to maximum) and use Z height to accurately focus the sample edge (minimum
contrast).
Always focus your sample using the Z height. If you move areas or tilt, refocus by pressing
Eucentric Focus and then use Z buttons. Only use the “Focus” knobs sparingly at very high
magnification and reset Eucentric focus often. Why is this?
Eucentric Focus and why it is so important. Eucentric focus is the key to correct alignment
of the microscope and serves two important functions. Firstly, it is the sample “height” (up and
down relative to the column) that intersects the Alpha Tilt axis, so when you tilt, the sample does
not orbit the axis but rotates around it. In practical terms this means that when you tilt in Alpha,
the region of interest does not appear to move. This is the original meaning of Eucentric, “well
centred”. Secondly, because this mechanical position is critical, the Objective Lens is designed
to be in focus, at this height (or plane) when it is operating at its Optimum setting of excitation
(about 90%). The objective lens is the most critical lens of the main column lenses and to acheive
the “best” resolution, must be operated at this setting (Focus setting). Based on this, the rest
of the microscope, from the Condenser lenses down to the final Projection lens, are focussed /
aligned. So if you erroneously focus the sample with the “Focus” control instead of Z, expect only
miserable images. The “Eucentric Focus” button simply resets the objective lens to the ideal value.
Set the magnification greater than 40,000. Focus the beam to
a spot using Intensity (LHCP). In the Align workset, select
Beam Shift and centre the beam (MFX, MFY). Click Done.
Tecnai F20 Quick reference guide
March 4, 2013
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Condenser Aperture Alignment
Observe the illumination as you change the Intensity L-R of focussed. Is it expanding and
contracting around a point (screen centre) or else swinging side to side? If the latter, adjust the
Condenser aperture position slightly using the multifuntion knobs, whilst rotating Intensity.
Get the spot to stop moving as you change Intensity.
Before using an aperture mechanism,
Enable the system by clicking the
named button.
To insert / select an aperture, click
on the dropdown and select the size,
which will then insert.
To enable MFX, MFY to adjust the
aperture position, click on Adjust.
Remeber to deselect the Adjust when
you are finished,
Which Condenser Aperture to use?
For normal C-TEM imaging and SAD work, you will use the largest CA, 150um. Smaller CA are used for
different experiments, in particular convergent beam electron diffraction (CBED) and STEM (50um).
Condenser astigmatism
As you focus C2 with the Intensity knob, observe the spot
shape. Is is constantly (approximately) round or does it become
oval? If it is oval when out of focus, select the Stigmators and
click Condenser. Adjust MFX, MFY to maintain a round
illumination spot. Click None to deselect stigmators.
Tecnai F20 Quick reference guide
March 4, 2013
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Gun alignment with Gun Tilt
Select Gun Tilt and using MFX, MFY, adjust
for the brightest beam by eye or by observing the
Exp. time (make it as short as possible) or Screen:
current (make it as large as possible). Typically the
Exp. time will be less than 1s (0.5 ~ 0.6).
Gun Shift alignment
When the spot size is changed, the beam position may move. To reduce this we carry out the
Gun Shift direct alignment.
1. Select spot size 9 (R3) and then back to size 8 (L3), focus the beam to a spot (Intensity)
and then at the highest magnification where you can still see the beam on the screen,
select Beam Shift and centre the spot, then click Done
2. Select Spot size 1 (L3) and focus to a spot
(Intensity)
3. Select Gun Shift, centre the spot
then click Done
4. Iterate 1 - 4 until your adjustments make no
improvement, using up to ~250,000 times mag.
Remember: LARGE spot = SMALL number = GUN SHIFT
SMALL spot = LARGE number = BEAM SHIFT
Tecnai F20 Quick reference guide
March 4, 2013
• 35
Saved Alignments
One very useful feature of the Tecnai microscopes is the ability to save and restore the
complete microscope alignment (as well as stage positions if required) to the PC hard disk.
So if you manage to completely mess up the alignment, it can be restored to near perfection
by simply loading the “latest” stored alignment.
MCEM staff will carry out an alignment periodically and save it with the name “Latest”.
This is generally the file to load. There may be other files present in the list, for example
alignments at voltages other than 200 kV. Do not load them unless you specifically require
them (please ask first).
To load an alignment, select the Alignment menu and on the flapout click File. Locate “Latest”
and click to select it. The available saved alignments are listed in the RH pane.Select all
(click + CTRL-A), promote them to the LH pane with the < button and click APPLY.
Although it is possible to save your own alignments, please DO NOT do this without asking
permission. User saved alignments will be deleted. If you do need a special alignment for
any reason please request MCEM staff assistance.
Tecnai F20 Quick reference guide
March 4, 2013
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Pivot Points
Ensure focus is eucentric. At a moderately high magnification
(50,000 ~ 250,000) select Beam shift, centre the beam, focus
to a spot, select Beam Tilt PP X. The beam will split and
oscillate. Us the MFX, MFY to make the split spots coincident.
Click Done and repeat for Beam Tilt PP Y. Re-centre the
beam with Beam shift.
Rotation Centre
Rotation Centre is used to optimise the overall optical path through the microscope, so that
for example electrons of slightly different energy (= wavelength) will come to a focus at
the same point. The Tecnai instruments use a “current centre” approach; by oscillating the
objective lens excitation current (focus) and observing what happens, we can “tune out” the
off-axis alignment error by means of beam deflection coils.
At a moderately high magnification (50,000 ~ 250,000), spread
the beam to cover the screen using Intensity. Find a sharp,
recognisable image feature and centre it (Joystick). Z (height)
focus accurately at Eucentric Focus and then finely with the
Focus knob (RHCP). Select Rotation Centre and defocus the
intensity so that you can only just see the feature using the
binoculars. Adjust MFX, MFY to minimise the apparent image
movement. It should appear to go in and out of focus only, no lateral movement. Click Done.
Objective lens astigmatism
At high magnification (Mh ranges), click Eucentric Focus and
focus the sample carefully (minimum constrast) using Z. Have
C2 adjusted to illuminate the entire scren. Select Stigmators
and click Objective. Using the small screen or CCD camera
(TIA or DM), defocus slightly with the Focus knob and adjust
the Objective Stigmator for best resolution, or use the Live
FFT function in the CCD software. Click None to deselect
Tecnai F20 Quick reference guide
March 4, 2013
• 37
Tecnai stigmator controls
A very nice feature of the Tecnai UI is the Stigmator controls.
The three stigmators (Condenser, Objective, Diffraction) each
have three memory locations, the current active one is selected
with a mouse click and indicated by an outline. If you have a
“good” setting but want to try a bit harder, you can copy this
setting to another location by a RIGHT click, then edit one
of the copies (R click on 1 allows you to copy it to 2 or 3,
etc.). To revert, simply click the original memory. When you
are finished, click None to disconnect the MF knobs from the
stigmators.
Diffraction
Diffraction mode is selected by the corresponding RHP button.
Firstly, either insert and centre a suitable slected area (SA)
aperture and defocus the illumination fully (C2 Intensity CW,
LHP) or focus the beam to a spot on the region of interest
and then press Diffraction. In the first case you will observe a
SADP (spot pattern) and in the second, a rough CBED pattern.
For CBED you may also wish to chenge the condenser aperture
to a smaller one and / or use a smaller spot size (RHP R3).
In Diffraction, MFX, MFY default to diffraction shift to position the DP on the screen.
Focus (RHP) becomes diffraction focus. Ensure that you always focus the sample first in
image mode at eucentric focus before selecting diffraction mode. To correct projector lens
astigmatism (ensure a sharp SADP spot), remove the SA aperture and translate to a large
hole in the sample. Fully defocus C2 and select Diffraction. Dofocus the Caustic Image
slightly and select Stigmator, Diffraction. Use MFX, MFY to correct astigmatism and then
focus to a sharp spot.
Tecnai F20 Quick reference guide
March 4, 2013
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Compustage Alpha and Beta tilt controls
The Tecnai F20 Compustage can tilt around one or two axes, depending on the holder used.
The standard holder is a Single Tilting type that can tilt +/- 35° around the Alpha (A) axis.
Provided that the sample is at the Eucentric height, the sample will not move very much
during tilting.
The low background (Be) double tilting holder can tilt +/- 35° in A and also +/- 25° in
Beta (B), orthogonal to A. The holder can tilt to these maxima in both axes simultaneously.
The copper (non low-background) double tilting holder has the same limitiations as the Be
version.
You must be very careful when tilting near to the A or B maxima to not exceed these limits!
It is possible that the holder might touch the Objective lens or apertures, causing damage.
Always tilt gradually, observing the values. Listen for the tilt limit warning “Beep” alarm.
If you hear it, IMMEDIATELY stop tilting, then press the OPPOSITE tilt direction to move
off the limit.
The Compustage RED LED will come ON when tilts exceed about 5 degrees in any direction.
This is normal and simply indicates that the holder CANNOT be removed without resetting
the holder (which you will normally do, of course).
Tilt directions (for the DP zone centre to move):
If the zone centre of your diffraction pattern
needs to move in a certain direction, refer to
these coordinates for which of the A, B tilt
buttons to press. We might refer to Alpha (R)
as + and Beta (T) as “+”.
The “+” buttons have a small dot on the
centre so you can locate it by feel (like a
Tecnai F20 Quick reference guide
March 4, 2013
• 39
Alpha and Beta tilt limitations using objective apertures
The Tecnai F20 Compustage tilt limitations (+/- 35° A, +/- 25° B) apply only when there
is no objective aperture inserted (the aperture size is irrelevant). When you are using an
objective aperture (for Dark Field work or diffraction contrast), you MUST keep to the
reduced tilt limits:
AlphaBeta
Objective Aperture OUT
+/- 35°
+/- 25°
Objective Aperture IN
+/- 35°
+/- 20°
Always remove the objective aperture before tilting A or B and check the limits before
inserting.
Tecnai F20 Quick reference guide
March 4, 2013
• 40
Tecnai automated apertures
The Tecnai F20 has Four sets of moveable (user adjustable) column apertures: the first
Condenser lens (C1, top), Second Condenser lens (C2, upper), Objective lens (OL, middle)
and Selected Area (SA, Intermediate lens, bottom). Unlike the T20, the apertures are
controlled by software, there are no manual adjuster screws.
The Condenser apertures are used to
limit the probe current and also the size of
discs in CBED mode. C2 ontrols the beam
convergence angle because with the beam
focussed to a spot, a larger C2 aperture
provides a larger exit aperture of the probe
forming optics. For CBED, the largest C2
aperture should be used provided the CBED
discs do not overlap.
The Objective aperture (OA) limits the
angular range of beams used to form the
image. It is located at the OL back focal plane
(i.e. where the diffraction pattern is formed).
With no OA, all available beams form the
image and resolution is maximised. On
the other hand the smallest OA will pass
only ~1 beam and is used for dark field
imaging (or simple BF) with maximum
contrast. An intermediate size of OA will
add considerable diffraction contrast (but
limit resolution) and is helpful for imaging
at lower magnifications.
The Selected Area aperture is located at the first OL image plane and is used only to select
the image region used to form selected area diffraction patterns (SADP).
Tecnai F20 Quick reference guide
March 4, 2013
• 41
Changing apertures
The F20 apertures
are fully motorised.
Both insertion and
adjustment are done
with the Apertures
menu.
The Condenser apertures 1 and 2 cannot be removed completely, whereas the Objective and
Selected Area apertures can. Generally the largest C1 aperture, 2000um, is selected.
The largest C2 (150um) is used for TEM and STEM alignment. The smallest C2 (50um) is
used for HR-STEM.
To insert (or change) an aperture, first click the Enable button to Yellow. Then select the
desired aperture with the drop-down menus. The Objective and Selected Area apertures can
then be inserted / retracted by the named button.
Before exchanging sample holders, ensure that the Objective Aperture is removed!
Adjusting apertures
The aperture positions are adjusted using the MFX, MFY knobs. Click the Adjust button
next to the aperture requiring adjustment. The MFX, MFY knobs are activated and are used
to move the aperture. Deselect the Adjust button by clicking (grey).
Tecnai F20 Quick reference guide
March 4, 2013
• 42
The F20 Aperture sizes are:
4321
C12000um100um50um30um
C2150um100um70um50um
OA100um40um20um10um
SA
800um200um40um10um ?
Convergence angles
Need to put angles in here?
Tecnai F20 Quick reference guide
March 4, 2013
• 43
Recording CCD images and diffraction patterns
The side-mounted Orius SC200D CCD camera is designed for both image and diffraction
pattern (including SADP) acquisition. Its design is resistant to electron beam damage and
also high intesities do not cause “flare” in the images. The SC200D is not a high resolution
camera, as its 2k x 2k sensor covers a large field of view (wide angle). Lattice images can
only be recorded at relatively high indicated magnifications (>400,000 times, preferably
620,000 times).
The bottom-mounted Ultrascan 1000 is for image acquisition only (NO DIFFRACTION!)
Due to the smaller angle it is a “high resolution” camera and as such much better for lattice
imaging than the SC200D.
In Digital Micrograph (DM), select the camera that you intend to use from the Camera
menu. When you want to change cameras, retract the other one first and stop acquiring.
The viewing screen must be raised when using the Ultrascan. Press the button on the LH
of the viewing chamber to raise / lower the screen or press L2. Always lower the screen
when changing magnification or the intensity, to avoid damaging the camera. The Ultrascan
resolution is lowered in search mode (512 x 512 binning). Use ~1s (acquire) exposures.
Raise / lower the main fluorescent screen
when using bottom mounted Ultrascan
camera by clicking R1 or pressing the button
LH of viewing chamber
Tecnai F20 Quick reference guide
March 4, 2013
• 44
Using the Bruker X-Ray Microanalysis system (EDS)
A Bruker XFlash 6130T Silicon Drift Detector (SDD) together with the Esprit Software,
has been installed on the Tecnai F20. The detector is a 30mm2 Windowless type giving 123
eV resolution @ Mn Ka and with enhanced light element sensitivity down to boron. It is
robust and able to accommodate higher input X-ray count rates without loss of poerformance
compared to the older Si(Li) detectors. Furthermore it is Peltier cooled rather than LN2 and
is retractable from the sample area under software motor control.
The Bruker EDS system can be used in both TEM mode (point and acquire) or STEM modes
(point or scanned acquisition).
When operating the F20 in TEM mode, the system can acquire single spectra from regions
on your sample limited by the beam area. For example using a defocussed beam allows large
areas to be analysed; converesely, focusing the beam to a small spot -as well as changing the
spot size to a smaller value- can permit analysis of individual particles.
Whilst larger spot sizes (meaning higher beam current) increase the X-ray count rate, beyond
a certain value, artifacts and acquisition time both increase. An optimum beam current is
when the “Dead Time” is around 30%. Lower dead times, from smaller spots, just increase
the time required to meet the requirement for good statistics.
If you are acquiring X-ray spectra from Cu-containing samples, use the Be double tilting
holder only (if you have samples on holey carbon grids, you will always have some Cu
background).
The detector is optimised for use at eucentric height and an Alpha tilt of 15 ~ 20°. Whilst it
might work at other angles (zero, or even slightly negative Alpha tilt), collection efficiency
will be greatly reduced and background (Cu, for example) may dominate the spectrum.
Tecnai F20 Quick reference guide
March 4, 2013
• 45
Operating in STEM mode
Operating in STEM requires two adjustments: Firstly, the FEG conditions are changed
by loading the 4500V STEM FEG register (FEG REG). Secondly, the column optics are
switched into STEM mode (this will initially happen automatically upon loading the FEG
register). Once the FEG REG has been loaded, the microscope can be switched back into
TEM without changing the FEG REG, for example to find a thin area or tilt a crystal.
Setting up
1) Check the log book entries, fill the ACD dewar. On the Vac / HT menu, find the FEG
Control menu and FEG Registers. If the instrument was last used in TEM, they will look
like this:
2) Click on STEM in the list under Lbl, then click SET. The F20 will now switch into STEM
(clicking noises) and the FEG will ramp up to 4500 EV. The FEG will take some time (30
min or so) to stabilise, so do this step at the beginning of your session.
As well as setting the FEG and Column, the Condenser Aperture will be set to 50um and the
HAADF detector will insert. You’ll hear some noises. Although the F20 is now configured
to acquire STEM images, we need to change several settings temporarily in order to set up
the alignment.
Tecnai F20 Quick reference guide
March 4, 2013
• 46
3) Plasma-clean your sample after loading it into the holder, 2 ~ 5min of Ar / O2 is good.
Load the sample into the microscope.
4) Switch the F20 back into TEM (STEM button grey)
6) Set the Condenser 2 aperture to 150um in the Apertures
menu.
7) Carry out your initial sample work (finding a good area, tilting to zone axis) in TEM as
it is much easier. If you use the Orius WA camera at all, retract it before starting STEM.
Note, although the Column is now in TEM, the gun still has the STEM settings. This is
OK, as you will not be trying to do any HRTEM.
8) Click on STEM, the F20 will switch to STEM mode and the HAADF detector will
insert. Set STEM magnification to 450,000 or more.
9) Now you need to find a thin amorphous region (if possible) or at least a thin edge. There
are 2 ways to do this:
Either, in the viewing screen, use the small screen and binoculars OR start scanning and
find a thin area. I recommend the first (unless you are a long way from a good region, in
which case scan and search).
Tecnai F20 Quick reference guide
March 4, 2013
• 47
10) In the binoculars, observe the diffraction pattern (CBED disk). Deselect Diffraction
(RHCP) and check that Focus Intensity and Objective is selected.
11) You should see some approximation of a Ronchigram;
defocus Intensity (C2) a long way (CW) and then you
can see the sample in “normal TEM” (albeit with a poor
quality image). Check Eucentric height (if not already
set above at 6) ) with Alpha Wobbler (L1).
12) Now adjust Objective focus (RHCP) to focus the image to Gaussian (~ minimum
contrast). Don’t touch Objective Focus any more! All (fine) STEM focussing is done with
the probe, C2 focus, Intensity knob. Use about 30~60,000 magnification.
Note: If the sample height is variable OR you tilt the sample, you may need to reset the
Eucentric Height, because this alignment procedure assumes that the sample is Eucentric
(and so all focussing changes are small).
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March 4, 2013
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STEM Gun alignment (best coherence / high resolution)
13) Focus the probe to a spot with Intensity. Now align the Gun (Tilt) as follows.
14) Mark the spot centre with beam stopper (BS). Adjust the
Gun Lens from 6 (STEM default) to 8 whilst observing the
spot.
-If it does not move off the BS, the gun is well aligned.
-If it does move, use the Gun Tilt (MFX, MFY) to re-centre
it. Then adjust Gun Lens from 8 to 4 whilst observing the spot.
-If it does not move off the BS, the gun is well aligned: set Gun Lens to 6 and exit this
procedure.
-If it moved, use the Beam Shift direct alignment to re-centre it. Adjust the Gun Lens from
4 back to 8, observing as before and correcting any shift with the Gun Tilt.
-Iterate until the spot does not move with any Gun Lens adjustment.
Remember: Use Gun Tilt when going UP in gun lens number and use Beam shift when
going DOWN in gun lens number
Tecnai F20 Quick reference guide
March 4, 2013
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15) Switch back to Diffraction. Refocus the Ronchigram with Intensity.
16) Select Stigmators and adjust the Condenser Stigmator (MFX, MFY) to produce the
most rounded Ronchigram with a “flat” or rather featureless disk. In addition, if you are
observing a good amorphous carbon film, you can reduce the detail in the ronchigram by
good stigmation until you see more or less uniform (flat) contrast in the centre at the “best”
Stigmator setting. Deselect Stigmators.
17) Select Rotation Centre (Objective) and observe the Ronchigram, which should go in
and out of focus about the centre, without displacement. Adjust with MFX, MFY.
18) Select Rotation Centre (Intensity) and observe the Ronchigram, which should go in
and out of focus about the centre, without displacement. Adjust with MFX, MFY.
19) Mark the Ronchigram centre with the beam stop. Insert and then centre the 50um aperture
on the mark. Remove the stop.
20) Ensure that the HAADF detector is inserted. Using the MFX, MFY (diffraction shift),
centre the diffraction pattern within the HAADF aperture.
21) In the TIA STEM window, click on SEARCH. You should see a reasonably wellfocussed STEM DF image.
Optimising the STEM settings
22)
Reduce
the
STEM
magnification to 10 ~ 20,000
and find a hole. Increase the
magnification so the hole covers
the field of view. Adjust the
Brightness to give Intensity
~5000 in the STEM Detector
Histogram window. This sets the
“vacuum” or no sample black
level.
Tecnai F20 Quick reference guide
March 4, 2013
• 50
STEM Gun lens and probe formation
The F20 Gun lens acts in a similar way to the spot size control (C1 lens).
When the gun lens is weakly
excited (left hand diagram), the
crossover occurs lower down
the column, allowing more total
current through the C2 aperture
but with higher aberrations. The
mode is used in HRTEM where
the aberrations are then rendered
unimportant by the defocussed
beam.
In STEM, where a very bright
(higher current density) probe
of lower aberration is needed,
a more strongly excited gun
lens is used. The crossover
occurs higher up the column,
reducing gun lens and condenser
aberrations.
The F20 FEG REG automatically sets the correct extraction voltage and Gun Lens excition
for TEM and STEM modes.
Tecnai F20 Quick reference guide
March 4, 2013
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23) Find a very bright region (thick part of the sample) and adjust Contrast to give Intensity
~50,000 in the Histogram. This allows for a large dynamic range without saturating the
detector. Do not adjust these values during your session, as they will give the best dynamic
range in the images.
STEM Detectors
There are two detectors for STEM imaging, the
Fischione HAADF detector mounted on the top of the
chamber and the Gatan Bright Field / Dark Field, located
under the bottom Orius 600 CCD. Both detectors can be
used simultaneously, by selection in TIA. The HAADF
detector image settings are done in TIA whereas the
Gatan is controlled by two knobs on the front panel.
PM Gain
Brightness
The HAADF insertion /
retraction is done by TIA
(Insert Detectors button).
IN (BF), IN (DF), OUT
The Gatan detector motion is controlled by 3 buttons shown above. The Gatan BF/DF detector collection angles are chosen to provide diffraction contrast, as in
BF/DF TEM. There is little or no atomic number contrast. On the other hand the HAADF
detector operated at the correct (short) camera length, provides mainly atomic number (Z)
contrast, with little diffraction contrast. The image interpretation is thus greatly simplified
compared to the strong and confusing diffraction contrast in conventional STEM and TEM
images.
The BF detector is invaluable in initial setting up, locating a ROI, and focussing. It also
assists in comparisons of TEM and STEM data.
To adjust the Gatan BF/DF, set AUTO brightness (pull out the RH knob) and adjust the
photomultiplier Gain (LH knob) to give a satisfactory image.
Tecnai F20 Quick reference guide
March 4, 2013
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Convergance and collection angles
The STEM probe convergence angle with the 50um aperture is 9.33 mrad.
Fischione HAADF detector at different camera lengths, L (mm)
70 mm the inner collection angle is 81mrad
80 mm the inner collection angle is 71mrad
100 mm the inner collection angle is 57mrad
150 mm the inner collection angle is 41mrad
200 mm the inner collection angle is 32mrad
General tips for good high-resolution HAADF STEM images
For good STEM images, the STEM Gun alignment, Condenser astigmatism, Eucentric
focus and crystal orientation are critical. In particular the crystal alignment (zone axis)
should be within about the diameter of the 50um C2 aperture CBED disk. Use a camera
length of 100 or 150mm for HAADF-STEM.
If you don’t see any fringes at first, move at lower magnification to a brighter region =
closer to ZA. Check the CBED pattern and re-tilt if needed. In STEM the tilt axis are
reversed compared to TEM: Alpha tilts L-R, Beta Up-Down and the directions are also
reversed.
When you find fringes, check Condenser Stigmator. Go in/out of C2 focus, observing the
fringes. If they change by ~90° either side of focus, adjust Condenser astigmatism.
If you can only get 1-D fringes anywhere and you expect (should be able to resolve) 2-D,
suspect the crystal orientation first, Condenser astigmatism second and Gun alignment
next.
Do all this and you should see < 2Å lattice images.
Enjoy. Don’t break.
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Saving and transferring data
All CCD data must be saved to the networked X: drive (physically, this hard drive is located
on the Bruker EDS Esprit system PC, not the microscope operating PC). The data cannot be
stored there long-term and at the end of the session you MUST either burn the data to a CD/
DVD-ROM or else copy it to the network N: drive.
The N: drive is accessible from any computer on the Monash network and is provided by
MCEM for TEMPORARY data storage only. Once you are back in your lab. / office OR in
the MCEM computer centre, copy your data off the N:drive to CD or a permanent storage
location.
Any data files left on the Tecnai PC, Support PC or N: drive are liable to be deleted without
warning and are not backed up by MCEM!
Please remember that USB removable memory (flash, hard drive etc) may not be used within
the Centre.
We recommend keeping CD/DVD copies of all your images in addition to hard drive (on
your own PC).
Save all your data BEFORE shutting down the Tecnai, not after the following user arrives!!
YOU are responsible for your own data, not MCEM.
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Ending your session
At the end of a normal session (not last user of the evening), please leave the microscope in
a standard (and tidy) state for the next user.
This is the best order in which to do things:
1. Save all your images to the N: drive. No permanent storage is available on the Tecnai PC
and files are liable to deletion at any time. Copy them to CD-ROM if required using the
PCs in the Computer Centre.
2. If you are working in STEM, leave the instrument in STEM and the STEM FEG setting,
but stop scanning (click off SEARCH). Retract HAADF and BF/DF, switch off Gatan
BF/DF boxes
3. If you are in TEM, leave the instrument in TEM.
4. Set maximum magnification, and if in TEM, centre the illumination and spread beam to
cover the screen (C2 ~50%).
5. Remove objective and selected area apertures if used (TEM).
6. Reset the Compustage XYZAB to zero and confirm this visually in the UI.
7. Stop all CCD acquisitions and retract all CCD cameras (do NOT warm up CCD).
8. Close Column valves.
9. Cover the viewing screen.
10.Open the hutch so that you can replace the holder in its stand.
11.Remove the sample holder as described above and remove your sample. Store the holder
in the correct place (dry box or pumping station), DO NOT leave it in the hutch!
12.Fill in the log book and Tidy the Lab.
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ACD Cryocycle
The anti-contaminator device, ACD or “Cold Trap”, is warmed to room temperature once
every 24 hours of operation. This allows water and volatiles to be pumped away. The ACD
heating / pumping is done automatically over a 4 hour period during which no microscope
operations are possible. The gun (HT) remains ON during a cryocycle.
1. Insert the blanking plug into the Compustage, set as Single Tilt, allow it to pump fully (3
cycles) and then switch the Turbo off.
2. Click CryoCycle in the vacuum CP
Cryo flapout.
The Turbo pump will start up and
after 8 minutes delay the column ion
pump will switch off, allowing the
evaporated contaminants on the trap to
be pumped away.
3. ! Cover the RHP and monitor with a plastic sheet and viewing screen with the rubber
cover. Put on your PPE !
4. Remove the ACD Dewar, placing a plastic beaker and hand towel under the copper braid
to catch the drips of LN2 and then empty the blue Dewar contents into the 2 l stainless steel
transport Dewar and place the blue Dewar ON ITS SIDE on the desk (not upright).
5. Remove and fold up the plastic sheet (and you can remove your PPE...).
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Vacuum and HT Problems
It is possible that when loading or unloading a sample holder, you may accidentally introduce
a brief air leak that affects the column vacuum. For this reason the Column Valves are
ALWAYS closed during the loading procedure.
If a leak occurs, it will be either:
a) small enough so that the microscope will run normally, with the column pressure fluctuating
for brief perid only and then recovering;
b) small but constant, with the column pressure abnormal and either constant or rising;
c) very large, with the column IGP1 turning off immediately
Actions:
a) Observe the reading for IGP1 and provided that it is no higher than 20 and is clearly
falling, wait for it to reach 6 and continue your work. Do not open the column valves until it
reads 6. This is similar to normal loading operations.
b) If, after 5 minutes or so, IGP1 is not back to 6 OR if it remains static at a higher value OR
rises AT ALL, remove the holder (turn off Turbo first) and examine the O-ring for hairs etc.,
before attempting a holder reload. Before reloading wait for IGP1 to reach 6. If it does not
reach 6 within 15 minutes, cancel the session and contact MCEM staff.
c) If IGP1 shuts down (you will hear various valves operating and see the IGP1 colour in the
Vacuum overview display change to dark blue) IMMEDIATELY remove the holder (Turbo
off first) and contact MCEM staff. If (out of hours) you cannot obtain help, wait for the
column vacuum to recover to IGP1 ON status (IGP1 has a ready) then start the CRYO cycle.
Cancel the session.
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If at any stage during operation, the HT turns off (trip), the session must be cancelled.
Please contact MCEM staff if possible and make a detailed note in the log book about what
happened and if you think there were any reasons for the trip (for example a sample holder
loading accident, or a mains power fluctuation!).
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