electron microscopes - universitetet i oslo...bseii come from a greater depth from within the...
TRANSCRIPT
![Page 1: Electron microscopes - Universitetet i oslo...BSEII come from a greater depth from within the specimen after undergoing multiple accumulative elastic interactions, ultimately emerging](https://reader034.vdocuments.us/reader034/viewer/2022042102/5e7f003e0f5ff022506e293a/html5/thumbnails/1.jpg)
Electron microscopes
MEF3100 Spring 2007
![Page 2: Electron microscopes - Universitetet i oslo...BSEII come from a greater depth from within the specimen after undergoing multiple accumulative elastic interactions, ultimately emerging](https://reader034.vdocuments.us/reader034/viewer/2022042102/5e7f003e0f5ff022506e293a/html5/thumbnails/2.jpg)
Bombard and analyze
MEF3100 Spring 2007
Sample
Electron gunDetector
![Page 3: Electron microscopes - Universitetet i oslo...BSEII come from a greater depth from within the specimen after undergoing multiple accumulative elastic interactions, ultimately emerging](https://reader034.vdocuments.us/reader034/viewer/2022042102/5e7f003e0f5ff022506e293a/html5/thumbnails/3.jpg)
SEM – Scanning electron microscope
MEF3100 Spring 2007
Quanta 200F from FEIField emissionESEMEDS
![Page 4: Electron microscopes - Universitetet i oslo...BSEII come from a greater depth from within the specimen after undergoing multiple accumulative elastic interactions, ultimately emerging](https://reader034.vdocuments.us/reader034/viewer/2022042102/5e7f003e0f5ff022506e293a/html5/thumbnails/4.jpg)
General outline for next 2 weeks - SEM
MEF3100 Spring 2007
Warming Up:• SEM History• Why use electron microscopes?• Some SEM examples
Beam specimen interaction
Images•Detectors •Contrast - Brightness•Image disturbances and their causes
Introduction:•How does the SEM work?•Resolution•Signal to noise• Wavelength, energy, speed ANALYTICAL SEM/Micro probe:
• Spectroscopy• EDS• WDSInstrument:
• Electron guns• Electron lenses• Probe size versus current
![Page 5: Electron microscopes - Universitetet i oslo...BSEII come from a greater depth from within the specimen after undergoing multiple accumulative elastic interactions, ultimately emerging](https://reader034.vdocuments.us/reader034/viewer/2022042102/5e7f003e0f5ff022506e293a/html5/thumbnails/5.jpg)
History
MEF3100 Spring 2007
1953-McMullan's Ph.D. Thesis 1962 -Cambridge InstrumentsThe first modern scanning electron microscope, constructed by D. McMullan in the Cambridge University Engineering Laboratory in1951.
Source: Electron Optics and Electron Microscopy, P.W. Hawkes.
![Page 6: Electron microscopes - Universitetet i oslo...BSEII come from a greater depth from within the specimen after undergoing multiple accumulative elastic interactions, ultimately emerging](https://reader034.vdocuments.us/reader034/viewer/2022042102/5e7f003e0f5ff022506e293a/html5/thumbnails/6.jpg)
Why use SEM and TEM?
MEF3100 Spring 2007
![Page 7: Electron microscopes - Universitetet i oslo...BSEII come from a greater depth from within the specimen after undergoing multiple accumulative elastic interactions, ultimately emerging](https://reader034.vdocuments.us/reader034/viewer/2022042102/5e7f003e0f5ff022506e293a/html5/thumbnails/7.jpg)
We will concentrate on:
MEF3100 Spring 2007
Secondary electrons =SE= picture, topographyBack scattered electrons =BSE= picture, chemistryCharacteristic X-rays =EDS= chemistry
![Page 8: Electron microscopes - Universitetet i oslo...BSEII come from a greater depth from within the specimen after undergoing multiple accumulative elastic interactions, ultimately emerging](https://reader034.vdocuments.us/reader034/viewer/2022042102/5e7f003e0f5ff022506e293a/html5/thumbnails/8.jpg)
Limits to Resolution
MEF3100 Spring 2007
• Unaided eye ~ 0.1 mm• Light microscope ~ 0.2 µm• Scanning EM ~ 1.0 nm• Transmission EM ~ 0.1 nm
![Page 9: Electron microscopes - Universitetet i oslo...BSEII come from a greater depth from within the specimen after undergoing multiple accumulative elastic interactions, ultimately emerging](https://reader034.vdocuments.us/reader034/viewer/2022042102/5e7f003e0f5ff022506e293a/html5/thumbnails/9.jpg)
Why use SEM?
MEF3100 Spring 2007
Optical microscope SEM
![Page 10: Electron microscopes - Universitetet i oslo...BSEII come from a greater depth from within the specimen after undergoing multiple accumulative elastic interactions, ultimately emerging](https://reader034.vdocuments.us/reader034/viewer/2022042102/5e7f003e0f5ff022506e293a/html5/thumbnails/10.jpg)
Example 1
MEF3100 Spring 2007
Secondary electron image of PbZr-oxide
![Page 11: Electron microscopes - Universitetet i oslo...BSEII come from a greater depth from within the specimen after undergoing multiple accumulative elastic interactions, ultimately emerging](https://reader034.vdocuments.us/reader034/viewer/2022042102/5e7f003e0f5ff022506e293a/html5/thumbnails/11.jpg)
Example 2 – BSE – Chemical contrast
MEF3100 Spring 2007
Back scatter image of gold on a polymer
![Page 12: Electron microscopes - Universitetet i oslo...BSEII come from a greater depth from within the specimen after undergoing multiple accumulative elastic interactions, ultimately emerging](https://reader034.vdocuments.us/reader034/viewer/2022042102/5e7f003e0f5ff022506e293a/html5/thumbnails/12.jpg)
Example 3 – EDS – chemistry:
MEF3100 Spring 2007
![Page 13: Electron microscopes - Universitetet i oslo...BSEII come from a greater depth from within the specimen after undergoing multiple accumulative elastic interactions, ultimately emerging](https://reader034.vdocuments.us/reader034/viewer/2022042102/5e7f003e0f5ff022506e293a/html5/thumbnails/13.jpg)
SEM is a strong tool for material characterization
MEF3100 Spring 2007
![Page 14: Electron microscopes - Universitetet i oslo...BSEII come from a greater depth from within the specimen after undergoing multiple accumulative elastic interactions, ultimately emerging](https://reader034.vdocuments.us/reader034/viewer/2022042102/5e7f003e0f5ff022506e293a/html5/thumbnails/14.jpg)
How does the SEM work?
MEF3100 Spring 2007
Probe gun
Secondary electron detector
Raster system
![Page 15: Electron microscopes - Universitetet i oslo...BSEII come from a greater depth from within the specimen after undergoing multiple accumulative elastic interactions, ultimately emerging](https://reader034.vdocuments.us/reader034/viewer/2022042102/5e7f003e0f5ff022506e293a/html5/thumbnails/15.jpg)
SEM cross section
MEF3100 Spring 2007
![Page 16: Electron microscopes - Universitetet i oslo...BSEII come from a greater depth from within the specimen after undergoing multiple accumulative elastic interactions, ultimately emerging](https://reader034.vdocuments.us/reader034/viewer/2022042102/5e7f003e0f5ff022506e293a/html5/thumbnails/16.jpg)
Magnification in SEM:
MEF3100 Spring 2007
![Page 17: Electron microscopes - Universitetet i oslo...BSEII come from a greater depth from within the specimen after undergoing multiple accumulative elastic interactions, ultimately emerging](https://reader034.vdocuments.us/reader034/viewer/2022042102/5e7f003e0f5ff022506e293a/html5/thumbnails/17.jpg)
MEF3100 Spring 2007
Increasing the magnification by reducing the size of the area being scanned
![Page 18: Electron microscopes - Universitetet i oslo...BSEII come from a greater depth from within the specimen after undergoing multiple accumulative elastic interactions, ultimately emerging](https://reader034.vdocuments.us/reader034/viewer/2022042102/5e7f003e0f5ff022506e293a/html5/thumbnails/18.jpg)
Abbe and resolution
MEF3100 Spring 2007
![Page 19: Electron microscopes - Universitetet i oslo...BSEII come from a greater depth from within the specimen after undergoing multiple accumulative elastic interactions, ultimately emerging](https://reader034.vdocuments.us/reader034/viewer/2022042102/5e7f003e0f5ff022506e293a/html5/thumbnails/19.jpg)
Signal to noise
MEF3100 Spring 2007
![Page 20: Electron microscopes - Universitetet i oslo...BSEII come from a greater depth from within the specimen after undergoing multiple accumulative elastic interactions, ultimately emerging](https://reader034.vdocuments.us/reader034/viewer/2022042102/5e7f003e0f5ff022506e293a/html5/thumbnails/20.jpg)
Signal to noise – scan time
MEF3100 Spring 2007
![Page 21: Electron microscopes - Universitetet i oslo...BSEII come from a greater depth from within the specimen after undergoing multiple accumulative elastic interactions, ultimately emerging](https://reader034.vdocuments.us/reader034/viewer/2022042102/5e7f003e0f5ff022506e293a/html5/thumbnails/21.jpg)
Wave length for electrons
MEF3100 Spring 2007
![Page 22: Electron microscopes - Universitetet i oslo...BSEII come from a greater depth from within the specimen after undergoing multiple accumulative elastic interactions, ultimately emerging](https://reader034.vdocuments.us/reader034/viewer/2022042102/5e7f003e0f5ff022506e293a/html5/thumbnails/22.jpg)
Wavelength of e-beam
MEF3100 Spring 2007
ρλ
emh
2= Substituting actual values:Accelerating
Voltage (kV)Nonrelativistic
wavelength (nm)
5 0.01830 0.007
Increasing the accelerating voltage decreases the wavelength of the electrons.
)2(mev ρ
= For 30 kV v~ 0.3 c
![Page 23: Electron microscopes - Universitetet i oslo...BSEII come from a greater depth from within the specimen after undergoing multiple accumulative elastic interactions, ultimately emerging](https://reader034.vdocuments.us/reader034/viewer/2022042102/5e7f003e0f5ff022506e293a/html5/thumbnails/23.jpg)
Instrument
MEF3100 Spring 2007
• Vacuum• Electron gun• Optics • Detectors
• Sample• Operator
![Page 24: Electron microscopes - Universitetet i oslo...BSEII come from a greater depth from within the specimen after undergoing multiple accumulative elastic interactions, ultimately emerging](https://reader034.vdocuments.us/reader034/viewer/2022042102/5e7f003e0f5ff022506e293a/html5/thumbnails/24.jpg)
Elektronkanon og Brightness
MEF3100 Spring 2007
For å kunne detektere maksimum signal velgervi materialer som gir så kraftig elektronstrålesom mulig.
brightness= maksimum signaler avhengig av flere parametere:ie - emisjonsstrømmenDo - elektronstrålens diameter – første cross-overαo - spredningen av elektronene
Vi vil ha høy emisjonsstrøm og liten diameter på kilden.
![Page 25: Electron microscopes - Universitetet i oslo...BSEII come from a greater depth from within the specimen after undergoing multiple accumulative elastic interactions, ultimately emerging](https://reader034.vdocuments.us/reader034/viewer/2022042102/5e7f003e0f5ff022506e293a/html5/thumbnails/25.jpg)
Lens system
MEF3100 Spring 2007
Condensor lens -determines beam current and "possible" spot sizeObjective lens, or final or probe forming lens,
determines the final spot size.Fixed Condensor aperture(s)Selectable final (objective) apertureElectrostatic lens in gun forms the first
crossover.Electromagnetic lens as condensor and
objective.EM are converging lenses –(i.e. parallel electron beam will converge to a
focal point at focal length f).–Diverging beam will be made to converge.
![Page 26: Electron microscopes - Universitetet i oslo...BSEII come from a greater depth from within the specimen after undergoing multiple accumulative elastic interactions, ultimately emerging](https://reader034.vdocuments.us/reader034/viewer/2022042102/5e7f003e0f5ff022506e293a/html5/thumbnails/26.jpg)
Condensor lens – spot size
MEF3100 Spring 2007
What happens if we make C1 weaker?
![Page 27: Electron microscopes - Universitetet i oslo...BSEII come from a greater depth from within the specimen after undergoing multiple accumulative elastic interactions, ultimately emerging](https://reader034.vdocuments.us/reader034/viewer/2022042102/5e7f003e0f5ff022506e293a/html5/thumbnails/27.jpg)
Condensor lens – spot size
MEF3100 Spring 2007
What happens if we make C2 stronger?
![Page 28: Electron microscopes - Universitetet i oslo...BSEII come from a greater depth from within the specimen after undergoing multiple accumulative elastic interactions, ultimately emerging](https://reader034.vdocuments.us/reader034/viewer/2022042102/5e7f003e0f5ff022506e293a/html5/thumbnails/28.jpg)
Condenser lens aperture
MEF3100 Spring 2007
Aperturen bestemmer hvor stor andel av strålen som treffer prøven. Den kontrollerer intensiteten. I SEM kontrollerer den også dybde i fokus.
![Page 29: Electron microscopes - Universitetet i oslo...BSEII come from a greater depth from within the specimen after undergoing multiple accumulative elastic interactions, ultimately emerging](https://reader034.vdocuments.us/reader034/viewer/2022042102/5e7f003e0f5ff022506e293a/html5/thumbnails/29.jpg)
Electron optics
MEF3100 Spring 2007
![Page 30: Electron microscopes - Universitetet i oslo...BSEII come from a greater depth from within the specimen after undergoing multiple accumulative elastic interactions, ultimately emerging](https://reader034.vdocuments.us/reader034/viewer/2022042102/5e7f003e0f5ff022506e293a/html5/thumbnails/30.jpg)
Summing up general concepts
MEF3100 Spring 2007
![Page 31: Electron microscopes - Universitetet i oslo...BSEII come from a greater depth from within the specimen after undergoing multiple accumulative elastic interactions, ultimately emerging](https://reader034.vdocuments.us/reader034/viewer/2022042102/5e7f003e0f5ff022506e293a/html5/thumbnails/31.jpg)
Interaction
MEF3100 Spring 2007
![Page 32: Electron microscopes - Universitetet i oslo...BSEII come from a greater depth from within the specimen after undergoing multiple accumulative elastic interactions, ultimately emerging](https://reader034.vdocuments.us/reader034/viewer/2022042102/5e7f003e0f5ff022506e293a/html5/thumbnails/32.jpg)
Sample – beam – Signals
MEF3100 Spring 2007
![Page 33: Electron microscopes - Universitetet i oslo...BSEII come from a greater depth from within the specimen after undergoing multiple accumulative elastic interactions, ultimately emerging](https://reader034.vdocuments.us/reader034/viewer/2022042102/5e7f003e0f5ff022506e293a/html5/thumbnails/33.jpg)
SEM – electron detection – charging
MEF3100 Spring 2007
![Page 34: Electron microscopes - Universitetet i oslo...BSEII come from a greater depth from within the specimen after undergoing multiple accumulative elastic interactions, ultimately emerging](https://reader034.vdocuments.us/reader034/viewer/2022042102/5e7f003e0f5ff022506e293a/html5/thumbnails/34.jpg)
Back scatter I
MEF3100 Spring 2007
![Page 35: Electron microscopes - Universitetet i oslo...BSEII come from a greater depth from within the specimen after undergoing multiple accumulative elastic interactions, ultimately emerging](https://reader034.vdocuments.us/reader034/viewer/2022042102/5e7f003e0f5ff022506e293a/html5/thumbnails/35.jpg)
Back scatter II
MEF3100 Spring 2007
![Page 36: Electron microscopes - Universitetet i oslo...BSEII come from a greater depth from within the specimen after undergoing multiple accumulative elastic interactions, ultimately emerging](https://reader034.vdocuments.us/reader034/viewer/2022042102/5e7f003e0f5ff022506e293a/html5/thumbnails/36.jpg)
Secondary electron
MEF3100 Spring 2007
![Page 37: Electron microscopes - Universitetet i oslo...BSEII come from a greater depth from within the specimen after undergoing multiple accumulative elastic interactions, ultimately emerging](https://reader034.vdocuments.us/reader034/viewer/2022042102/5e7f003e0f5ff022506e293a/html5/thumbnails/37.jpg)
SE II
MEF3100 Spring 2007
![Page 38: Electron microscopes - Universitetet i oslo...BSEII come from a greater depth from within the specimen after undergoing multiple accumulative elastic interactions, ultimately emerging](https://reader034.vdocuments.us/reader034/viewer/2022042102/5e7f003e0f5ff022506e293a/html5/thumbnails/38.jpg)
SE III
MEF3100 Spring 2007
![Page 39: Electron microscopes - Universitetet i oslo...BSEII come from a greater depth from within the specimen after undergoing multiple accumulative elastic interactions, ultimately emerging](https://reader034.vdocuments.us/reader034/viewer/2022042102/5e7f003e0f5ff022506e293a/html5/thumbnails/39.jpg)
SE I, II; III og BSE I ,II– influence on resolution
MEF3100 Spring 2007
Excitation of SE and BSE from within a specimen by the primary beam. SE and BSE trajectories are shown.(a) High accelerating voltage applied to the primary beam. BSEI emerge from close proximity to the beam impact area.BSEII come from a greater depth from within the specimen after undergoing multiple accumulative elastic interactions, ultimately emerging spatially disconnected from the point of impact of the beam. (b) Low accelerating voltage appliedto the primary beam. The primary electrons penetrate less into the specimen and therefore the BSEII emerge closer to the beam impact area and are more sensitive to the surface topology than at higher accelerating voltages.
![Page 40: Electron microscopes - Universitetet i oslo...BSEII come from a greater depth from within the specimen after undergoing multiple accumulative elastic interactions, ultimately emerging](https://reader034.vdocuments.us/reader034/viewer/2022042102/5e7f003e0f5ff022506e293a/html5/thumbnails/40.jpg)
Beam scattering – broadening
MEF3100 Spring 2007
![Page 41: Electron microscopes - Universitetet i oslo...BSEII come from a greater depth from within the specimen after undergoing multiple accumulative elastic interactions, ultimately emerging](https://reader034.vdocuments.us/reader034/viewer/2022042102/5e7f003e0f5ff022506e293a/html5/thumbnails/41.jpg)
Detektorer
MEF3100 Spring 2007
![Page 42: Electron microscopes - Universitetet i oslo...BSEII come from a greater depth from within the specimen after undergoing multiple accumulative elastic interactions, ultimately emerging](https://reader034.vdocuments.us/reader034/viewer/2022042102/5e7f003e0f5ff022506e293a/html5/thumbnails/42.jpg)
Everhart-Thornley Detector
MEF3100 Spring 2007
![Page 43: Electron microscopes - Universitetet i oslo...BSEII come from a greater depth from within the specimen after undergoing multiple accumulative elastic interactions, ultimately emerging](https://reader034.vdocuments.us/reader034/viewer/2022042102/5e7f003e0f5ff022506e293a/html5/thumbnails/43.jpg)
Everhart-Thornley Detector
MEF3100 Spring 2007
![Page 44: Electron microscopes - Universitetet i oslo...BSEII come from a greater depth from within the specimen after undergoing multiple accumulative elastic interactions, ultimately emerging](https://reader034.vdocuments.us/reader034/viewer/2022042102/5e7f003e0f5ff022506e293a/html5/thumbnails/44.jpg)
Everhart-Thornley Detector
MEF3100 Spring 2007
![Page 45: Electron microscopes - Universitetet i oslo...BSEII come from a greater depth from within the specimen after undergoing multiple accumulative elastic interactions, ultimately emerging](https://reader034.vdocuments.us/reader034/viewer/2022042102/5e7f003e0f5ff022506e293a/html5/thumbnails/45.jpg)
Back scatter electron detector
MEF3100 Spring 2007
A solid-state (semi-conductor) backscattered electron detector is energized by incident high energy electrons (~90% E0), wherein electron-hole pairs are generated and swept to opposite poles by an applied bias voltage. This charge is collected and input into an amplifier (gain of ~1000). The detector is positioned directly above the specimen, surrounding the opening through the polepiece