The New TEM facility at LCI, KSU

Min Gao

Liquid Crystal Institute

Kent State University

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Questions to be answered

• How does TEM work?

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• 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?

Facts about the TEM facility at LCI

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Instruments

Specifications

Applications

What we have at LCI

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• 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

How good is this microscope?

Borisevich, 2004

La in γ-Al2O3

Batson et al. Nature 2002

in situ

0.0001

0.001

0.01

0.1

1

1800 1840 1880 1920 1960 2000 2040

Reso

luti

on

(A

ng

.-1

)

Year

Electron Microscope

Light Microscope

Corrected EM

Ross

Amici

Abbe

Ruska

Marton

Dietrich

(200keV)

Haider

(200keV)

“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”

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• 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

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 bugs-easy to operate

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7

Philips and FEI microscopes

EM420

CM200

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“I've gotta see some atoms, excuse me,“ --Obama

Titan

How much a TEM cost?

• $4-5 per eV

• 200 keV: 1M$ + accessories (easily up to 0.5-1M)

There must be some solid reasons that we need such an expensive machine!

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.

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How does TEM work?

Importance of thin specimens

Electron-material interaction

Techniques and Information

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50 nm Cu, 25 kV, 5 nm probe, 1000 electrons 50 nm Cu, 200 kV, 1 nm probe, 1000 electrons

Advantage of thin samples

Thin specimen in SEM (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

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Generally speaking: 50-100 nm for conventional TEM; 15 nm for high resolution TEM

How to put the thin samples into the TEM?

• The general form of a TEM specimen is a 3mm thin disk

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Supporting grids

• Put the thin disk into a holder which goes to the TEM sample stage

How to prepare a thin sample?

• Bulk materials: Agate Mortar and Pestle

Wheel Saw Polishing machine

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Dimpler

Ion milling A lot of techniques have been developed to make TEM specimens

• Bulk & thin films:

Focused ion beam: TEM samples

Deposition of Pt protection layer

View from 52°

Start of cutting

Under cut

Au+Pd coating first

Other materials

Nanomaterials:

• Very easy

• Dispersed on supporting carbon film

Biomaterials

• Quite difficult

• Vitrobot

• Ultramicrotomy

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Specimen

Electron-thin specimen interaction

E

E-E

Ef

Characteristic X-rays

EDS

EELS

EFTEM

E

Secondary electrons

Auger electrons

Backscattered Electrons (Rutherford)

Large-angle Incoherent elastically scattered electrons (Rutherford)

Z-contrast

STEM

Light

Cathodoluminescence

e-h pair

EBIC

Inelastically scattered electrons Coherent elastically scattered electrons

Diffraction

Imaging

HRTEM

Other signals from interaction with many nuclei or electrons: Bremsstrahlung x-ray (EDS), Plasma excitation (EELS) …

Incident

electron

beam (E)

Ef Ef Ef

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Reimer, TEM, 1984

Instruments (TEM & STEM)

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O Si Mo

Information from a modern TEM

Gao et al. APL, 72, 2544 (1998)

Gao et al. JAP, 80, 4767 (1996)

Gao & Duan, Mater. Trans. JIM, 39, 883, 1998

Gao et al. PRB, 62, 5413 (2000) Gao et al. Unpublished

Gao et al. Z. Metallkd. 93, 438 (2002)

In situ

EELS/EDS

Si

CBED

Mo/SiOx

Gao et al. PRB, 62, 5413 (2000)

O-K 1s 2p

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Why TEM?

Knowing the limitations of TEM

• 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

• Artifacts due to 2-D projections (3D TEM)

• Electron beam irradiation and contamination (diffraction imaging, low temperature, low dose, cryoEM)

• Poor Sampling: all TEMs have only examined <1 mm3 of materials! (First use low resolution but better sampling tools)

• Interpretation of images

What have been done in the test running period at LCI?

Service summary

Available techniques

Representative results

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Si_L

C_K O_K

Au+Si+O

Serv

ice

ho

urs

Nu

mb

er

of

sam

ple

s

Week

Weekly service hours and number of samples

Total service hours: 186 Cryo: 83 hrs

Total number of samples: 113 FE

I Cry

o T

rain

ing

Min

in C

hin

a

Cry

o-t

rial

Ho

liday

TEM

Sta

rtu

p

1%6%4%

20%

4%

8%30%

3%4%

20%

Peter Palffy-Muhoray

Quan Li

Oleg Lavrentovich

Tony Jakli

Soumitra Basu

Service hours vs groups

L.C. Chen

Mieteck Jaroniec

Songping Huang

Laurie Broadwater

Teaching

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

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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 Palffy-Muhoray’s group

HRTEM of

quantum dots

Sample from Prof. LC Chien’s group

Diffraction

30 Sample from Dr. Quan Li’s group

An interesting

sample SiOx

C

Au

Sample from Prof. Peter Palffy-Muhoray’s group

EDS spectral imaging

Au

Si

O

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

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Plan for the next step

• 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

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• Soon be running regularly

– Rules and operation procedures

– Usage rates (machine use, staff service) and billing

– …

• Web page of the facility

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 • …

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Questions being answered

• How does TEM work?

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• 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? mgao@kent.edu