The New TEM facility at LCI, KSU

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The New TEM facility at LCI, KSU
Min Gao
Liquid Crystal Institute
Kent State University
1
Questions to be answered
• How does TEM work?
• Why thin specimen?
How to prepare one?
• What is the TEM at LCI like?
Functions available and principles?
• How is the facility running so far?
Any exciting results?
• How to use the TEM lab?
2
Facts about the TEM facility at LCI
Instruments
Specifications
Applications
3
What we have at LCI
• FEI Tecnai F20ST-STEM
–
–
–
–
–
Schottky field mission gun
40 kV-200 kV
0.24 nm point-to-point resolution
±70° tilting angle
0.2 nm spot size
• Attachments
– Low-dose mode & tomography
– EDAX energy dispersive x-ray
spectrometer (EDS)
– Gatan imaging filter (incl. EELS)
– 4k*4K slow scan CCD
– Cryo-holder & anti-contaminator
• Assisting equipments
– Vitrobot
– Plasma cleaner
– Vacuum station
4
How good is this microscope?
“It would be very easy to make an analysis of any complicated chemical substance; all one would have to
do would be to look at it and see where the atoms are. … I put this out as a challenge: Is there no way to
make the electron microscope more powerful?”
– Richard P. Feynman, 1959, “There’s Plenty of Room at the Bottom”
Corrected EM
in situ
Haider
(200keV)
1
Dietrich
(200keV)
0.1
Electron Microscope
-1
Resolution (Ang.)
La in γ-Al2O3
Marton
0.01
Borisevich, 2004
0.001
Light Microscope
Ruska
Abbe
0.0001
Amici
Ross
1800 1840 1880 1920 1960 2000 2040
Year
Batson et al. Nature
2002
• Second best thing after corrected TEM
• It is the best thing considering
• Cost of TEM and maintenance
• Easy to use
• 85% applications do not need Cs corrector
5
General description of the TEM facility
at LCI
• Things making this facility standing out: the
optimum integration of some most advanced
TEM techniques, for example: cryoEM
• An application-oriented versatile microscope
• Excellent for materials science/life science/solid
state physics/chemistry
• Current setup: nanomaterials/soft-materials
requiring simple sample preparation
• A heavily computerized TEM with some bugseasy to operate
6
Philips and FEI microscopes
EM420
CM200
7
“I've gotta see some atoms, excuse me,“
--Obama
Titan
8
How much a TEM cost?
• $4-5 per eV
• 200 keV: 1M$ + accessories (easily up to 0.51M)
extremely stable high-voltage supplies, extremely stable currents to each
electromagnetic coil/lens, continuously-pumped high- or ultra-high-vacuum systems,
and a cooling water supply circulation through the lenses and pumps. As they are very
sensitive to vibration and external magnetic fields, microscopes designed to achieve
high resolutions must be housed in stable buildings (sometimes underground) with
special services such as magnetic field cancelling systems.
There must be some solid reasons that we need
such an expensive machine!
9
How does TEM work?
Importance of thin specimens
Electron-material interaction
Techniques and Information
10
Advantage of thin samples
50 nm Cu, 25 kV, 5 nm probe, 1000 electrons
Thin specimen in SEM
50 nm Cu, 200 kV, 1 nm probe, 1000 electrons
(Thin specimen in) TEM
 Where is my surface? Surface damage
11
What thin samples do you need?
• Represent the material you are studying: sometimes
the thicker the better
• Electron transparent: dependent on the accelerating
voltage, thickness of the specimen, and atomic
number of the specimen.
• Uniformly thin
• Stable under the electron beam
• Conducing and nonmagnetic in the laboratory environment
Generally speaking: 50-100 nm for conventional TEM;
15 nm for high resolution TEM
12
How to put the thin samples into the
TEM?
• The general form of a TEM
specimen is a  3mm thin disk
Supporting
grids
• Put the thin disk into a holder
which goes to the TEM sample
stage
13
How to prepare a thin sample?
• Bulk materials:
Agate Mortar and Pestle
• Bulk & thin films:
Wheel Saw
Polishing machine
Ion milling
Dimpler
A lot of techniques have been
developed to make TEM specimens
14
Focused ion beam: TEM samples
Au+Pd coating first
Deposition of
Pt protection
layer
Start of
cutting
View from 52°
Under cut
Other materials
Nanomaterials:
Biomaterials
• Very easy
• Quite difficult
• Dispersed on
supporting carbon film
• Vitrobot
• Ultramicrotomy
16
Electron-thin specimen interaction
Cathodoluminescence
Incident
electron
beam (E)
Backscattered
Electrons
(Rutherford)
Characteristic Xrays
EDS
Ef
Ef
Ef
E
E
Secondary
electrons
Light
Auger
electrons
Ef
e-h pair
EBIC
Specimen
Large-angle Incoherent
elastically scattered
electrons (Rutherford)
Z-contrast
STEM
E-E
Coherent elastically
scattered electrons
Diffraction
Imaging
HRTEM
Inelastically scattered electrons
Other signals from interaction with many nuclei or
electrons: Bremsstrahlung x-ray (EDS), Plasma
excitation (EELS) …
EELS
EFTEM
17
Instruments (TEM & STEM)
Reimer, TEM, 1984
18
Information from a modern TEM
Gao et al. PRB, 62, 5413 (2000)
Gao et al. Unpublished
In situ
Why TEM?
Gao et al. APL, 72, 2544 (1998)
CBED
Gao et al. JAP, 80, 4767 (1996)
Gao et al. Z. Metallkd. 93, 438 (2002)
EELS
/EDS
Gao et al.
PRB, 62, 5413
(2000)
O-K 1s  2p
O
Si
Mo
Mo/SiOx
Si
Gao & Duan, Mater. Trans. JIM, 39, 883, 1998
19
Knowing the limitations of TEM
• Artifacts due to 2-D projections
(3D TEM)
• Interpretation of images
• Poor Sampling: all TEMs have only examined <1 mm3 of materials!
(First use low resolution but better sampling tools)
• Electron beam irradiation and contamination (diffraction imaging,
low temperature, low dose, cryoEM)
• Sample preparation (low temperature, low-energy low angle ion
milling, FIB-site specific, freeze-fracture, vitreous ethane ice)
• Vacuum environment (environmental EM, in vitro)
• Not so much about properties (in situ, combination)
20
Au+Si+O
Si_L
C_K
O_K
What have been done in the test
running period at LCI?
Service summary
Available techniques
Representative results
21
Number of samples
FEI Cryo Training
Min in China
Cryo-trial
Holiday
TEM Startup
Service hours
Weekly service hours and number of samples
Week
Total service hours: 186
Cryo: 83 hrs
Total number of samples: 113
Service hours vs groups
Soumitra BasuTeaching
Laurie Broadwater
6%1%
4%
Songping Huang
Mieteck Jaroniec
20%
20%
4%
8%
L.C. Chen
Peter Palffy-Muhoray
4%
3%
30%
Quan Li
Oleg Lavrentovich
Tony Jakli
Available TEM techniques
• Imaging (diffraction contract,
high resolution, Z-contrast,
energy-filtered)
• Diffraction (select-area,
convergent beam, large angle
CBED, nano-area)
• Spectrometry (EDS, EELS)
• CryoEM
• 3D tomography
• …
24
Imaging (contrast)
• Mass and thickness contrast
• Diffraction contrast
• Phase contrast (e.g., HRTEM)
• Z-contrast
25
Imaging
(LCI)
TEM bright field image and
STEM Z-contrast (dark field) image
Sample from Prof. Peter Palffy-Muhoray’s group
HRTEM
Sample from
Prof. Peter
PalffyMuhoray’s
group
HRTEM
of
quantum
dots
Sample from Prof. LC
Chien’s group
Diffraction
Sample from Dr. Quan Li’s
group
30
An
interesting
sample
C
SiOx
Au
Sample from Prof. Peter Palffy-Muhoray’s group
EDS spectral imaging
O
Au
Si
Au+Si+O
Si_L
C_K
O_K
Sample from Prof. Peter Palffy-Muhoray’s group
Cryo-Vitrobot
– Controlled environment: temperature
(4-60°C) and humidity (room cond. –
100%)
– designed for bio and liquid
– A small droplet of liquid is applied to
pre-treated carbon film
– Two filter papers are used to blot the
liquid and leave a thin layer of liquid
(e.g., 100 nm thick, adjustable blot
force, time and repetition).
– Shoot the sample into coolant (ethane)
and freeze it at very high speed.
First bio-sample
Laurie Broadwater, Chemistry
A thermotropic sample
Sample from Prof. LC Chien’s group
A lyotropic sample
Sample from Prof. Oleg Lavrentovich’s group
• Resolution beyond freeze fracture
• Very challenging: <10 e/nm2
Sample from Prof. Jakli’s group
Diffraction in Liquid Crystals
Larger area
Sample from Prof. Jakli’s group
3D tomography
• A video taken by Dr. Lee Pullan (FEI) during the
cryoEM training
39
Plan for the next step
• Soon be running regularly
– Rules and operation procedures
– Usage rates (machine use, staff service) and billing
–…
• Self-user Training:
– Single operator  MG + several self-users
– Right now: 1-on-1 based on research needs
– Later: a TEM course including lab training if allowed
• Web page of the facility
40
How to use the facility more efficiently
• Highly efficient, professional, yet friendly service
• The TEM will be aligned by the staff routinely, so you do not
need to be an expert in TEM
• Know your sample as well as possible
• If you don’t know TEM so well, have an in-depth discussion
with the staff before scheduling your experiment
• Have a student with good experimental skills and a lot of
patience
• Analyze your data immediately
• Introduce more outside users to keep the rates low
• Acknowledge the facility properly
• Pay your bill in time 
• …
41
Questions being answered
• How does TEM work?
• Why thin specimen?
How to prepare one?
• What is the TEM at LCI like?
Functions available and principles?
• How is the facility running so far?
Any exciting results?
• How to use the TEM lab?
[email protected]
42
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