MAT_SCI 360
Introduction to Electron Microscopy
Fall 2013
TEM Laboratory 1:
Introduction to TEM, Basic TEM operation and Electron Diffraction
This laboratory is designed to introduce one of the basic transmission electron microscopes, a Hitachi H-8100 Transmission Electron Microscope. In this initial laboratory, methods for basic operation and alignment of the instrument will be covered. You will also observe methods for sample preparation (covered in the first Introduction and Safety Tour).
The purpose of this lab is to get you familiar with the standard operation of the TEM and general facility practices.
As you know from the course lectures, a TEM is to generate and analyze the electrons scattered by electron-specimen interactions. Electrons scattered to different angles as a function of the sample orientation, thickness, composition (and more) yield different contrast in images. For this first laboratory, we will only be collecting imaging showing massthickness and diffraction contrast.
Learning Objectives: By the end of this laboratory session, you should be able to:
1.
Load TEM grids onto the sample holder; and Insert/Take out the holder into the H-
8100 TEM.
2.
Adjust Gun-Tilt, Gun-Shift, Condenser Lens Aperture and Condenser Lens Astigmatism to get a well-aligned electron beam.
3.
Set up Eucentric height, Adjust the Beam-Tilt and Objective lens Astigmatism to get a high quality TEM image.
4.
Do basic selected-area electron diffraction, by using the selected-area aperture.
5.
Do basic bright-field imaging by put in objective aperture and select the transmitted beam.
6.
Do basic dark-field imaging by put in objective aperture and select the diffracted beams.
Lab Background: Review of some basic principals you learnt in the class and/or are in the textbook:
1.
Electron source: There are two kinds of commonly used electron sources 1)
Thermionic electron gun using W and LaB
6
as the filament and 2) Field emission gun
(single crystal W).
2.
Brightness: electron beam brightness is defined as the electron current per unit area and unit solid angle. The figure below shows the relationship between the emission current/brightness vs the bias voltage (voltage of the Wehnelt):

Fig.1. Definition of beam brightness; and schematic relationship between bias voltage, emission current and beam brightness (after Goldstein and Yakowitz, 1975, p.25)
3.
Defects of a magnetic lenses: spherical aberration refers to the lens imperfections which lead to different focal lengths in center and at edges of lens
Fig.2. Illustration of spherical aberration of a lens.
4.
Defects of a magnetic lenses: astigmatism refers to lens defect caused by magnetic
Fig.3. Illustration of a lens’ astigmatism. field asymmetry.
5.
Chromatic Aberration: additional blurring due to energy spread in the electron beam, lens current and high voltage instabilities.

Fig.4. Illustration of a chromatic aberration.
6.
Deflection coils: provide a means to shift or to tilt the electron beam. They can be used to correct some of the mechanical misalignments of the optical system, or to obtain specific imaging effects, but not all misalignments. They are many different shift/tilt coils, for instanfce the Gun Coils, Beam Coils, Image Coils and Scanning
Coil etc.
7.
Interaction of high energy electron with specimen is a complicated process. Signals generated in such interactions include secondary electron (SE), backscattered electron, X-rays, Auger electrons, visible light, transmitted electrons, transmitted and elastically scatted electron and transmitted and inelastically scatted electron.
8.
While and image is formed in the focal plane of the objective lens, electron diffraction can be obtained from the back-focal plan of the objective lens. Electron diffraction can be used to study crystalline structures. You need some basic crystallography knowledge to interpret the electron diffraction patterns (more will be covered in the second TEM lab and the lectures).
1.
Basic safety issues (Before coming for your TEM labs, please read details about safety at http://www.nuance.northwestern.edu/epic/download/temh8100.pdf)
 Emergency evacuation
 Chemical contamination
 Electric shock
 Other safety issues: read departmental safety plan, EPIC facility rules and TEM lab safety draft. Sign the safety training sheet.
2.
Login/reserve/logout FOM system
Visit http://www.fom.northwestern.edu/NUANCE/login.asp from any internet connected computer
Use mse360 as user ID, account number and password

3.
Sample preparation equipment (Contact Drs. Jinsong Wu and Shuyou Li at EPIC when you need help on TEM sample preparation)
 Cutting: wheel saw, wire saw, ultrasonic cutters…
 Polishing: mechanical polishing, electro-chemical polishing…
 Dimpling: Gatan dimple grinder
 Ion milling: PIPS, IBT
 Microtome
4.
Basic TEM operations (Please download H8100 TEM operation manual from http://www.nuance.northwestern.edu/epic/download/tem-h8100.pdf bring it with you for all TEM labs) and
 Microscope startup
 Obtaining good electron illumination
 Setting the sample at eucentric height
 Condenser lens alignment
 Beam tilt purity (compensation)
 Objective lens alignment (Voltage center)
 Image focus and astigmatism correction (Fresnel-fringe method)
 TEM shutdown
5. Selected area (SA) electron diffraction
 Find and center an interesting area
 Insert and center a suitable SA aperture
 SA aperture is focused in SA mode
 Press Diff.
 Form a parallel illumination on the sample by turning Brightness counterclockwise.
 Focus the pattern by adjusting intermediate lens current I1 to
 Record a few SA diffraction pattern with different exposure time.
 If CCD camera is used, make sure that the CCD camera is not saturated. Tip:
Start with very short exposure time and use beam stopper. (When CCD camera is saturated, there is a streaking across the direct spot).
In your laboratory report you should provide a description of all micrographs taken and give a concise discussion of differences you see. The lectures and your textbook should be sufficient for you to interpret your results, but you should provide an explanation in your own words. It is recommended to break your report into different sections including Introduction, Experimental, Results, Discussion etc.
In your Experimental section, you will need to
1). Acquire a normal TEM image of the Au nanoparticles;
2). Acquire a bright-field TEM image of the Au Nnaoparticles;
3). Acquire a dark-filed TEM image of the Au nanoparticles;

4). Acquire a selected area diffraction pattern from Au particles and index the diffraction rings (write down necessary TEM parameters).
In addition to a discussion about the images, your lab report should provide answers to the following questions:
1.
Index the diffraction pattern below (describe the whole procedure) and give possible crystal structure and zone axis index
2.
When you find that the illumination is low (i.e. not much intensity), what do you need to check? Both the Probe Size and the condenser lens aperture can both be used to increase the Brightness. Please explain what the effects of adjusting Probe
Size are, and what the effects of adjusting the condenser aperture area.
3.
The electron beam alignment in TEM is achieved by using deflectors. Draw a diagram to show how to shift a beam.
4.
Gun-Tilt and Beam-Tilt are used for TEM alignment. Describe the function and effects of Gun-Tilt and Beam-Tilt. With a drawing, compare their similarities and differences.
5.
In an electron diffraction experiment using graphite the larger ring formed by rows of carbon atoms 1.23 x 10 -10 m apart appeared at an angle of 0.167 radian, what is the electron wavelength?
6.
From Abbe’s equation, the point resolution of an optical system is approximately half of the wavelength of imaging radiation. Why is the Abbe’s prediction not realized in a TEM?

H8100 Daily Operation Guide
Last modified on June 2013 by Dr. Jinsong Wu
Note: This guide is NOT complete operation manual of H8100. It is only for your daily operation quick reference. For detailed operation manual, please refer to http://www.nuance.northwestern.edu/epic/manuals.htm
Remember:
1.
Please send a copy of your publication (e-format preferred) to Jinsong (jinsongwu@northwestern.edu) if you use any TEM results taken with this microscope! We highly appreciate if you include NU ANCE Center in the Acknowledgement.
2.
Adjust the alignment settings ONLY when necessary.
3.
Refill Liquid Nitrogen if your experiment goes over 2 hours.
BEFORE YOU START

Check conditions of H8100 before login the access control. (Turn on Panel Lamp at right side of control panel if necessary) o Vacuum lights (Gun=green, column=green, specimen=yellow, camera=green); o Sample position (X=0, Y=0, tilt=0), Apertures position (Condenser=1, Objective=0, Selected area=0); o
Filament=OFF, HV=200 (CRT), probesize=micro3, Zoom (left panel) &Bright (right panel) ON.

Check FOM records to see notes left by previous user.
START-UP
1.
Fill LN2, Log in Access Control in FOM, http://www.fom.northwestern.edu/.
2.
Turn off HV (press Acc. Voltage READY/OFF twice); Load Specimen. Remember to check the
O-ring!
3.
Turn on HV (press Acc. Voltage READY/OFF once), press 200KV to increase HV.
4.
Apply Filament Current SLOWLY (20 seconds per division). Stop at one division before maximum.
FIND BEAM
5.
Check emission current ( HV/BEAM meter, 0<current < 10

A .).
6.
Follow these steps to find the beam. Skip to next part (step 7) whenever you see the beam. o Dim or turn off room light. Remove cover of viewing chamber. Decrease
MAGNIFICATION to see if beam appears. If yes, go to next part (step 7). o Press LOW MAG . If you see the beam, move a hole on your specimen to the center of the screen. Focus the beam to small spot through the hole on the sample; go back to
ZOOM mode (press ZOOM). Adjust sample position and BRIGHTNESS to find the beam. o
Call for help if you still cannot find the beam.
CHECK Gun Tilt
7.
Change MAG to 20K. Adjust BRIGHTNESS to get the smallest beam spot.
8.
Center beam with BRIGHTNESS CENTERING . It should look like fig. 1a or 1b.
1a 1b 1c
9.
Adjust GUN TILT slowly and see the feature change. Try to find the brightest and the most symmetrical position of the beam (fig.1a). (Do not touch GUN HORIZ knob at this step!)
10.
Slowly increase Filament current until you see saturated beam as shown in fig. 1c.
CHECK Gun HORIZ
(To remember the knobs used in this step, “1C-4G”)
11.
Change MAG=8K. Make sure Probe Size on CRT is 3, center beam with BRIGHTNESS
CENTERING .
12.
Use SPOT SIZE knob (left sub panel) to select probe size 1 , center beam with BRIGHTNESS
CENTERING.
13.
Select probe size 5 , center beam with Gun Horiz .
14.
Repeat last two steps until beam is centered at both probe 1 and 5.
15.
Set probe size back 3 when finish alignment.
16.
Center beam with BRIGHTNESS CENTERING .
CHECK Condenser lens (C2) Aperture centering
17.
Change BRIGHTNESS largely back and forth to see how the beam image changes.

18.
If the beam spread and shrink uniformly like fig 2a, go to Find specimen part (step
23).
19.
If it changes from fig. 2b to fig. 2c with changing brightness : a). Focus the
3a
3b bean to the cross-over, center it by using
BRIGHTNESS CENTERING.
b). Spread the beam out by turning BRIGHTNESS knob clockwise; c). adjust C2 position knobs on the aperture handler to center the beam.
3c
CHECK Condenser lens stigmatism
20.
Change BRIGHTNESS largely back and forth to see how the beam image changes.
21.
If the beam spread and shrink uniformly like fig 3a, Skip to next part (step 23).
2a
2b
2c
22.
If it changes from fig. 3b to fig. 3c with changing brightness , adjust COND STIG until it spread and shrink uniformly as shown in fig. 3a.
FIND specimen and SET eucentric height
23.
Change MAG>=8K. Move specimen to find a small feature with sharp edge.
24.
Check OBJ current on the CRT and set it to 5.25
(adjust FOCUS or press reset under the CRT)
25.
Spread beam with BRIGHTNESS to cover whole screen, as long as you can still see specimen image.
26.
Turn on Wobbler (right panel) and the feature may vibrate.
27.
Adjust Thumb-screw on GONIOMETER to minimize the vibration.
28.
Turn off Wobbler when you finish.
Voltage Center Alignment
29.
Move specimen to find a very small feature with sharp edge on your specimen under MAG=10-
25K . Decrease or increase MAGNIFICATION if necessary. Use binocular if necessary.
30.
Spread beam with BRIGHTNESS to cover whole screen.
31.
Turn on CCD Camera (in Search Mode): refer to CCD instructions.
32.
Under CRT (left), make sure STOP button is lit on. Press PHOTO to raise viewing screen.
33.
Center the small feature to the center of CCD with Specimen transition knobs
34.
Turn on HV MODULATION (right panel). The image feature may vibrate. (Spread beam if you see beam vibrating other than image feature.)
35.
Adjust BEAM TILT (right sub panel) to minimize the vibration of the feature.
36.
Repeat last step at MAG 100k or higher if lattice imaging is needed.
37.
Turn off HV MODULATION .
Objective lens stigmatism
38.
Find and center a amorphous area in the CCD, under Process menu click Live and then Reduced
FFT;
Turn FOCUS knob (right panel) and watch for the inner circle in the FFT window; use OBJ STIG
X&Y knobs (left sub panel) to make the inner circle as round as possible (increase time to 0.9 s, if contrast of the ring is low). Tips: dark fringe (over focus), bright fringe (underfocus).
39.
Turn FOCUS knob to maximize the diameter of the inner circle in the FFT window. Now we are closed to the optimal focus value. Fine tune can be done by looking at the image carefully.
Take Picture
40.
Always take picture with underfocus (white edge).
41.
To take picture with digital CCD imaging, follow separate manual.
42.
To take picture with negatives, change exposure time (left of CRT) to AUTO and check exposure time on CRT. Typical time is less than 5 seconds. Make sure that the STOP light under CRT is
NOT lit. Press FEED and then PHOTO to take pictures.
Selected Area Diffraction (Skip if you don’t need SAED analysis)
43.
Find and center an interesting specimen area
44.
Insert and center a suitable SA APERTURE
45.
Press SA (left panel)

46.
Make sure that the * is at left corner of intermediate lens current I1 on the TEM monitor. If not, click UP/DOWN ARROW key to cancel any highlighted item on the TEM monitor. Input 5 from keyboard (left panel) and press RETURN. Focus SA aperture using DIFFRACTION SPOT knob (left panel) and binocular.
47.
Make sure that the STOP light on TEM data monitor is lit. If no, press STOP once to make it lit.
48.
Press DIFF (left panel). If the central spot is not at the viewing center, center it using the INTER
ALIGN X and Y knobs (left sub panel). If the spot is not round, make it round using INTER
STIG X and Y knobs.
49.
Spread beam by turning BRIGHTNESS counterclockwise. Diffraction spots will become weaker and smaller.
50.
Focus the pattern by adjusting DIFFRACTION SPOT (left panel).
51.
Record a few SA diffraction patterns the CCD. Please use the beam stop if the transmitted spot is too bright!!
Bright Field/Dark Field Imaging (Skip if you don’t need Dark Field imaging)
52.
Follow previous step, insert and center a suitable Objective aperture on Transmitted spot of
SAED pattern.
53.
Press ZOOM, remove SA aperture to see Bright Field image. Adjust focus and/or obj stigmatism if necessary.
54.
Check exposure time and take image (see step 41).
55.
Remove Obj aperture , insert SA aperture and press DIFF to go back to SAED mode. Center
Obj aperture to one diffractio spot .
56.
Repeat 52&53 to record Dark Field image. You may set manual exposure time if image is too dark.
TEM shutdown
57.
Turn MAG down to 8000, center beam and spread beam to cover whole screen.
58.
Move specimen to origin: X=0, Y=0, Tilt=0
59.
Turn MAG to 6K
60.
Slowly turn the Filament current to off (3 minutes)
61.
Press Acc. Voltage READY/OFF twice to switch HV off
62.
Check or set these settings to standby mode:
● OBJ aperture OUT ● SA aperture OUT ● Condenser aperture=1
63.
Make sure specimen position at origin, take specimen holder out of the column
64.
Remove specimen and insert specimen holder back to TEM till STOP position. Push EVAC switch to evacuate.
65.
If no negative film was used , turn on HV at 200kV, complete logbook and logout FOM software.
Go to next part if there are negative films to be developed.