(Electron) microscopy at MTM

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Transcript (Electron) microscopy at MTM

(Electron) microscopy at MTM

SIM² workshop HiTemp group – MTM Annelies Malfliet 23 January 2013

Content

• • • • Microscopy at MTM: in general Sample preparation In particular – – – – SEM XL30 FEG/XL40 LAB6 FEG-EPMA JXA-8530F TEM CM 200 FEG FEI Nova NanoSEM Contact details 23/01/2013 2

MICROSCOPY AT MTM

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Overview microscopy

• https://www.mtm.kuleuven.be/English/Research/Equipment/List#_Microscopy 23/01/2013 New µscope FEI Nova NanoSEM 4

Core facility ‘Electron microscopy’

• State-of-the-art Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) 23/01/2013 5

(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 23/01/2013 6

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) 23/01/2013 7

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 23/01/2013 8

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 • • not on SEM, but on Electron Probe Micro Analysis (EPMA) Higher spectral resolution • • Typically quantification with standards More time consuming (5 spectrometers  same time) up to 5 elements measured at the 23/01/2013 9

SEM - TEM

• Difference SEM – TEM – Higher eV with TEM  spatial resolution beam with smaller wavelength  higher – Observe electrons passed through (and interacted with) the sample – Much smaller and especially thinner sample electron source D = 3 mm sample screen 23/01/2013 10

Overview table

Light optical microscopy XL40 SEM LAB6 XL 30 SEM FEG XL30 ESEM FEG XL30 SEM + EBSD FEI Nova Nanosem JXA-8530F FEG-EPMA TEM CM 200 FEG

Imaging Phase composition Crystal structure/texture

EDS WDS EELS x x x x x x x x x x x x x x x x x x 23/01/2013 11

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 • 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 23/01/2013 12

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 23/01/2013 15

Sample preparation

• In general: for LOM/SEM/EBSD (room 02.33) – 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) – Grinding/polishing/OPS • 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 23/01/2013 grinding polishing 16

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 Mechanical polishing 23/01/2013 17

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 23/01/2013 18

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) • • Most frequent used EM – User-friendly – – Many users 1 day training – Reservation per 2 hour • 1-3 samples Many users  – highly occupied (24h/d; 7d/w) Alternative is SEM XL40 LaB 6 : • similar possibilities (SE/BSE, EDS, ...) • Particle analysis software • LaB 6 vs. FEG: LaB 6 has larger probe diameter and less brightness, but for many applications it can be sufficient • Almost not used 23/01/2013 XL30: BSE image + EDS analysis XL40: BSE image 21

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 @ MnK a – WDS system: 5 full scanner type X-ray spectrometers 23/01/2013 24

FEG-EPMA: Use

• • • Typical analysis type – Composition quantification using standards • Including minor and light elements – – Mapping elemental distribution Better spectral resolution  state of elements oxidation 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 FEG EPMA – For external and occasional measurements, technical responsible at MTM can do the measurement 23/01/2013 25

TRANSMISSION ELECTRON MICROSCOPY (TEM)

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TEM CM 200 FEG

• Details – – – 20-200 kV Resolution < nm EDS/EELS – GATAN Tridiem Image Filter • • Few users Several day training 23/01/2013 27

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 23/01/2013 28

FEI NOVA NANOSEM

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FEI Nova Nanosem

• FEI Nova Nanosem – Imaging (SEM with TLD) • High resolution • Low keV imaging • ‘Pure’ samples (not coated) • Difficult samples (magnetic, non-conductive) – – Chemical analysis (EDS) Phase/ texture analysis (EBSD) • • Chrystallographic characterisation Integration with EDS  phase analysis – Plasmacleaner • Just installed, about to be operational 23/01/2013 Anodized Ti EDS+EBSD 30

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 23/01/2013 32