electron microscopy for catalyst characterization dr. king lun yeung
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CENG 511 Lecture 3. Electron Microscopy for Catalyst Characterization Dr. King Lun Yeung Department of Chemical Engineering Hong Kong University of Science and Technology. Electron-Specimen Interaction. backscattered e - elemental contrast. e -. e -. secondary e - - PowerPoint PPT PresentationTRANSCRIPT
Electron Microscopy for Catalyst Characterization
Dr. King Lun YeungDepartment of Chemical Engineering
Hong Kong University of Science and Technology
CENG 511 Lecture 3
Electron-Specimen Interaction
e-
e-
e-
backscattered e-
elemental contrast
secondary e-
surface topography
Primary or unscattered e-
projected sample image transmission electron microscopyhttp://www.jeol.com/sem_gde/imgchng.html
http://www.unl.edu/CMRAcfem/http://www.ou.edu/research/electron/www-vl/
http://www.mwrn.com/guide/electron_microscopy/microscope.htm
Specimen Interaction Volume (Vi)
Augersecondary e-
backscattered e-
K X-rayL X-ray
incr
easi
ng d
epth surface information
bulk information
Vi when accelerating Vi when incident angle Vi when atomic number
Electron-Specimen Interaction
Backscattered electrons Topography (A-B)
Composition (A+B)
Electron-Specimen Interaction
Secondary electrons
Electron-Specimen Interaction
Ugly BUGS
Electron-Specimen Interaction
Surface Topography of Catalyst-related Materials
Electron-Specimen Interaction
Primary or unscattered electronsdiamond
gold
TEM
Electron-Specimen Interaction
e-
e-
e-
X-raysbulk elemental composition
Auger electronssurface elemental composition
Cathodaluminescenceband-gap energy, electronic property
http://jan.ucc.nau.edu/~wittke/Microprobe/ProbeNotes.html
Electron-Specimen Interaction
Cathodaluminescence
Electron-Specimen Interaction
Cathodaluminescence
Ion implanted silicon patterns
Electron-Specimen Interaction
X-rays
Sampling volumefor X-ray
X-rays
Si(Li) detector
Electron-Specimen Interaction
Si(Li) Detector
E Ne-
PULSE 1PULSE 2
Electron-Specimen Interaction
Si(Li) Detector Window
Electron-Specimen Interaction
Energy Dispersive X-ray Spectroscopy
Si (bright) Al (bright)
Electron-Specimen Interaction
http://jan.ucc.nau.edu/~wittke/Microprobe/Interact.html#Aug
Auger Electron
WK
WL
WM
WN
WG
K
K
L
Auger e-or
Auger e- Z
Scanning Electron Microscopy
specimen
Electron gun
SEM - Electron Gun
SEM - Electromagnetic Condenser Lenses
SEM - Electromagnetic Condenser Lenses
Figure C-8. The light optics (4) and scanning coils (1) are located inside the minicoil probe-forming lens (2) at the base of the electron column. The pole piece (7) is one solid piece of metal and protects the sample from stray magnetic fields. The x-ray beams (3) are collimated by small apertures (6), and pass through an electron trap (5) that prevents backscattered electrons from entering the x-ray pectrometers.
SEM - Objective Len
SEM - Electron Probe
SEM - Image Formation-1
SEM - Image Formation-2
Scanning Electron Microscopy
high voltage
low voltage
Effect of accelerating voltage
http://www.jeol.com/sem_gde/imgchng.html
Scanning Electron MicroscopyEffect of accelerating voltage
http://www.jeol.com/sem_gde/imgchng.html
Scanning Electron MicroscopyEffect of beam current and spot size
http://www.jeol.com/sem_gde/imgchng.html
Scanning Electron MicroscopyEffect of accelerating voltage
http://www.jeol.com/sem_gde/imgchng.html
Scanning Electron MicroscopyEffect of accelerating voltage
http://www.jeol.com/sem_gde/imgchng.html
Scanning Electron MicroscopyIncorrect alignment of objective aperture
http://www.jeol.com/sem_gde/imgchng.html
Scanning Electron MicroscopyEffect of specimen tilt
http://www.jeol.com/sem_gde/imgchng.html
Stereo microscopy
Scanning Electron MicroscopyEffect of accelerating voltage
http://www.jeol.com/sem_gde/imgchng.html
(1)
(2)
(3)
Scanning Electron MicroscopyContrast and brightness
http://www.jeol.com/sem_gde/imgchng.html
Scanning Electron MicroscopyAstigmatism
http://www.jeol.com/sem_gde/imgchng.html
Scanning Electron MicroscopySample charging
http://www.jeol.com/sem_gde/imgchng.html
Scanning Electron MicroscopyPreventing charging by thin film coating
http://www.jeol.com/sem_gde/imgchng.html
Scanning Electron MicroscopyElectron beam damages and contamination
http://www.jeol.com/sem_gde/imgchng.html
Carbon contaminant deposited by electron beam
Electron beam damage on afly’s compound eye
Scanning Electron MicroscopySources of image distortions
http://www.jeol.com/sem_gde/imgchng.html
Scanning Electron MicroscopyInfluence of external disturbances
http://www.jeol.com/sem_gde/imgchng.html
Scanning Electron MicroscopyImportance of sample preparation
http://www.jeol.com/sem_gde/imgchng.html
Electron-Specimen Interaction
e-
e-
e-
backscattered e-
elemental contrast
secondary e-
surface topography
Primary or unscattered e-
projected sample image transmission electron microscopyhttp://www.jeol.com/sem_gde/imgchng.html
http://www.unl.edu/CMRAcfem/http://www.ou.edu/research/electron/www-vl/
http://www.mwrn.com/guide/electron_microscopy/microscope.htm
Electron-Specimen Interaction
Principle of E. M. lithography
Polymer resist
Substrate
Electron Beam Lithography
Micropatterning and Microfabrication
PMMA resist
E-beam develop resist selectively etchsubstrate
http://www.cnf.cornell.edu/SPIEBook/spie5.htm#2.5.3.1
Microfabricated Catalysts
deposit alternate layers of catalyst and inert
micropattern and etch
undercut and remove
50 nm nickel, 50 nm SiO2
Supported Catalysts
Metal supported on metal oxide
Coarsening
Microfabricated CatalystsZeolite micropatterned catalysts
Zeolite Grids
(200)/(020) (101)
Zeolite Grids
Electron-Specimen Interaction
Electron beam
Thin sample
Unscatteredelectrons
Different Types of Electron Microscopy
SEM TEM Ultra-TEM
HREM
Transmission Electron Microscopy
Au/SiO2
http://www.mwrn.com/guide.htmhttp://www.hei.org/research/depts/aemi/micro.htm
Electron-Specimen Interaction
Transmission Electron Microscopy
Au
Transmission Electron Microscopy
Primary or unscattered electronsdiamond
gold
TEM
http://em-outreach.sdsc.edu/web-course
Transmission Electron Microscopy
Catalyst particle size distribution
Size (nm)
Transmission Electron Microscopy
Catalyst particle shape and morphology
Particle MorphologySelected zone dark field imaging (SZDF)
(100)
??
Particle MorphologySelected zone dark field imaging (SZDF)
(100)
(100)
(110)
Particle MorphologyWeak beam dark field (WBDF)
(100)
Particle MorphologySZDF and WBDF techniques
Electron-Specimen Interaction
Transmission Electron Microscopy
Distribution of crystallographic planes
Electron-Specimen Interaction
High Resolution Electron Microscopy
http://bnlstb.bio.bnl.gov/biodocs/stem/interactive.htmlx
Bismuth molybdates (Bi2Mo3O12-)
High Resolution Electron Microscopy
Bismuth molybdates (Bi2MoO6-)
High Resolution Electron Microscopy
Platinum on Alumina
hydrogen
Hydrogen sulfide
High Resolution Electron Microscopy
2 x 1 reconstruction of (110) surface of Au particle
High Resolution Electron Microscopy
Rh/SiO2
Reduced Oxidized
High Resolution Electron Microscopy
Rh particles
High Resolution Electron Microscopy
Electron-beam induced reduction of RuCl3 on MgO
High Resolution Electron Microscopy
Hydrogen reduced Rhodium-TiO2
Electron-Specimen Interaction