(Electron) microscopy at MTM

Report
(Electron) microscopy at MTM
SIM² workshop
HiTemp group – MTM
Annelies Malfliet
23 January 2013
Content
• Microscopy at MTM: in general
• Sample preparation
• In particular
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–
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SEM XL30 FEG/XL40 LAB6
FEG-EPMA JXA-8530F
TEM CM 200 FEG
FEI Nova NanoSEM
• Contact details
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MICROSCOPY AT MTM
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Overview microscopy
•
https://www.mtm.kuleuven.be/English/Research/Equipment/List#_Microscopy
New µscope
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FEI Nova NanoSEM
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Core facility ‘Electron microscopy’
• State-of-the-art Scanning Electron Microscopy (SEM) and
Transmission Electron Microscopy (TEM)
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(Electron) microscopy’
• Imaging: phase distribution, particle size, topography, ...
– Light Optical Microscopy (LOM)
– Secondary Electron (SE) or Backscattered Electron (BSE) imaging (on SEM)
– Bright-Field (BF) imaging (on TEM)
• Chemical analysis: phase composition, presence of impurity
elements, element distribution, ...
– Energy Dispersive Spectroscopy (EDS) (on SEM/TEM)
– Wavelength Dispersive Spectroscopy (WDS) (on FEG-EPMA)
– Electron Energy Loss Spectroscopy (EELS) (on TEM)
• Crystallography: crystal structure + texture
– Electron Backscatterd Diffraction (EBSD) (on SEM)
– Selected Area Electron Diffraction (SAED) or Convergent Beam Electron
Diffraction (CBED) (on TEM)
 Broad spectrum of equipment and preparation facilities
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Electron microscopy
• Difference LOM – EM
– Source: light vs. electrons
– Optical lenses vs. eletromagnetic lenses
– Eye vs. Detectors
• Resolution
• Most used electron microscope is Scanning Electron
Microscope (SEM)
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SEM detectors
• Typical detectors
– Secondary electron detector (SE)
• Good spatial resolution
• Topography
– Backscattered electron detector (BSE)
• Strong atomic number contrast
– X-ray detector
• Elemental analysis
• Different signals originate from different interaction volumes
• Effect of voltage on interaction volume
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Composition analysis
• Based on emission of characteristic X-rays caused by excitation from
eletron beam
• X-ray can be detected by:
– Energy Dispersive Spectroscopy
• X-ray are separated based on their energy
• Result is an energy-intensity spectron with peaks
– Peak position identifies the element
– Height ~ its concentration (standardless quantification)
• Energy resolution ~127eV
• Measuring time: 10-100s (all elements measured at the same time)
– Wavelength Dispersive Spectroscopy
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•
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not on SEM, but on Electron Probe Micro Analysis (EPMA)
Higher spectral resolution
Typically quantification with standards
More time consuming (5 spectrometers  up to 5 elements measured at the
same time)
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SEM - TEM
• Difference SEM – TEM
– Higher eV with TEM  beam with smaller wavelength  higher
spatial resolution
– Observe electrons passed through (and interacted with) the sample
– Much smaller and especially thinner sample
electron
source
D = 3 mm
sample
screen
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Overview table
Imaging
Phase composition
EDS
Light optical microscopy
x
XL40 SEM LAB6
x
x
XL 30 SEM FEG
x
x
XL30 ESEM FEG
x
x
XL30 SEM + EBSD
x
FEI Nova Nanosem
x
JXA-8530F FEG-EPMA
x
TEM CM 200 FEG
x
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WDS
Crystal
structure/texture
EELS
x
x
x
x
x
x
x
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Effort - information
• Microscopy technique is mainly determined by
– What information you would like to have
– Size of the features of interest
• Depending on technique, material and required sample
‘perfectness’, the parameters that determine effort are:
– Sample preparation
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•
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Embedding: 15 min – 1 day curing/ conductive resin (under pressure)
Grinding/polishing: hard/brittle/porous/soluble in water(ethanol)/...
Conductive coating needed: thickness, homogeneity
Preventing contamination (air, moisture): storing in
desiccator/vacuum/cryo cleaner/...
• Removing contamination: plasma cleaner/...
– Learning process
• Training
• Experience/practice!
• Literature reading
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Effort - information map
• In general ...
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SAMPLE PREPARATION
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Sample preparation at MTM
•
https://www.mtm.kuleuven.be/English/Research/Equipment/List#_Sample_preparation
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Sample preparation
• In general: for LOM/SEM/EBSD (room 02.33)
grinding
– Cutting
– Ultrasonic cleaning: remove particles from pores
– Embedding with
• Technovit: cures very fast (15 min)
• Epofix: better infiltrates pores  better for powder
or porous material (1 day curing under vacuum)
• Predopress (pressure/hot mounting): harder resin
 better for harder materials
(also conductive powder available for conductive resin
 no need for coating in case of conductive sample)
polishing
– Grinding/polishing/OPS
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•
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Manual or automatic
Cooling + removing debris: water/ethanol/oil
OPS: soft/ductile materials
Different materials require different grinding + polishing
procedure  best to talk with responsible technician
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Sample preparation
– Especially for evaluation of interfaces or for soft material:
Cross section ion polishing
• Clean surface on large area (~ 1 mm²)
• Disadvantage: more time consuming than mechanical polishing
Au
Ni-P
Cu
CP method
Polishing time: 4 hours
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Mechanical polishing
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Sample preparation
– Etching (for metals)
• In acid, electrolytically
– Coating with C/Au/Pt/Au-Pd/Pt-Pd
• Au-Pd: imaging surface topography/gives higher resolution
• C: Chemical analysis, mapping, EBSD
– Carbon rod: better suited for thin homogeneous layer than carbon wire
• For EDS/WDS: Pay attention to overlap of peaks of coating and sample
– Degassing in vacuum chamber
Coating units at MTM
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Sample preparation
• TEM: more complicated + different methods depending on
material
• Separate TEM sample preparation room at MTM
• Possible at MTM
– Thin film: grinding/polishing/thinning/breakthrough
(electrolytic,ion miller)
– Replica method
– Depositing on support grid
– Ultramicrotome to cut slices
– FIB
– ...
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SEM XL30 FEG/XL40 LAB6
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SEM XL30 FEG
• Equipment details
– 0.2-30 kV
– SE/BSE detector
– EDS (detection from B)
XL30: BSE image
+ EDS analysis
• Most frequent used EM
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–
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User-friendly
Many users
1 day training
Reservation per 2 hour
• 1-3 samples
• Many users  highly occupied (24h/d; 7d/w)
XL40: BSE image
– Alternative is SEM XL40 LaB6:
• similar possibilities (SE/BSE, EDS, ...)
• Particle analysis software
• LaB6 vs. FEG: LaB6 has larger probe diameter and less
brightness, but for many applications it can be sufficient
• Almost not used
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FEG-EPMA
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FEG-EPMA JEOL JXA 8530F
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Main features
• In-Lens Schottky Field Emission Gun (FEG)
– 1 - 30 kV, 50 pA – 500 nA, 40 nm minimum probe size
• Imaging
– Electron detectors: SE + BSE
• 40x to 300,000x magnification
– Cathodeluminescence system
• Monochromatic + panchromatic
• Phase composition
– EDS system: Resolution: 129 eV @ MnKa
– WDS system: 5 full scanner type X-ray spectrometers
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FEG-EPMA: Use
• Typical analysis type
– Composition quantification using standards
• Including minor and light elements
– Mapping elemental distribution
– Better spectral resolution  oxidation
state of elements
• 0.5-1 day/sample
– Possible to let it run overnight by setting
measurement points or mapping area
• 3-day training
– Users are through promotors of the FEGEPMA
– For external and occasional
measurements, technical responsible at
MTM can do the measurement
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TRANSMISSION ELECTRON
MICROSCOPY (TEM)
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TEM CM 200 FEG
• Details
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20-200 kV
Resolution < nm
EDS/EELS
GATAN Tridiem Image Filter
• Few users
• Several day training
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TEM: Use
• Characterization of nanoscale particles with respect to their
shape, size, structure, chemical composition and distribution.
– Imaging
– Diffraction: crystal structure
– Composition analysis
• EDS
• EELS: especially useful for light elements
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FEI NOVA NANOSEM
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FEI Nova Nanosem
• FEI Nova Nanosem
– Imaging (SEM with TLD)
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High resolution
Low keV imaging
‘Pure’ samples (not coated)
Difficult samples
(magnetic, non-conductive)
– Chemical analysis (EDS)
– Phase/ texture analysis (EBSD)
Anodized Ti
EDS+EBSD
• Chrystallographic characterisation
• Integration with EDS  phase analysis
– Plasmacleaner
• Just installed, about to be operational
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WHAT IF YOU WOULD LIKE TO USE ONE
OF THE MICROSCOPES AT MTM?
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Contact details
• For more information:
– Core facility Electron microscopy: Tom Van der Donck
([email protected])
– SEM XL30/XL40: Rudy De Vos ([email protected])
– [email protected]
• If you are advised to have a training, use the training request
form available at https://ppms.info/kuleuven/treq/?pf=2
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