Electron Microscopy for Catalyst Characterization Dr. King Lun Yeung

1. CENG 511 Lecture 3 Electron Microscopy for Catalyst Characterization Dr. King Lun Yeung Department of Chemical Engineering Hong Kong University of Science and Technology

2. Electron-Specimen Interaction backscattered e- elemental contrast e- e- secondary e- surface topography e- Primary or unscattered e- projected sample image transmission electron microscopy http://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

3. Auger secondary e- backscattered e- K X-ray L X-ray surface information increasing depth bulk information Specimen Interaction Volume (Vi) Vi when accelerating  Vi when incident angle  Vi when atomic number 

4. Topography (A-B) Composition (A+B) Electron-Specimen Interaction Backscattered electrons

5. Electron-Specimen Interaction Secondary electrons

6. Electron-Specimen Interaction Ugly BUGS

7. Electron-Specimen Interaction Surface Topography of Catalyst-related Materials

8. Electron-Specimen Interaction Primary or unscattered electrons diamond TEM gold

9. Electron-Specimen Interaction e- Cathodaluminescence band-gap energy, electronic property X-rays bulk elemental composition e- Auger electrons surface elemental composition e- http://jan.ucc.nau.edu/~wittke/Microprobe/ProbeNotes.html

10. Electron-Specimen Interaction Cathodaluminescence

11. Electron-Specimen Interaction Cathodaluminescence Ion implanted silicon patterns

12. Electron-Specimen Interaction X-rays Si(Li) detector X-rays Sampling volume for X-ray

13. Electron-Specimen Interaction Si(Li) Detector l  E   Ne-  PULSE 2 PULSE 1

14. Electron-Specimen Interaction Si(Li) Detector Window

15. Electron-Specimen Interaction Energy Dispersive X-ray Spectroscopy Si (bright) Al (bright)

16. Ka WK Kb La WL or Auger e- WM WN WG Electron-Specimen Interaction Auger Electron Auger e-  Z  http://jan.ucc.nau.edu/~wittke/Microprobe/Interact.html#Aug

17. Electron gun specimen Scanning Electron Microscopy

18. SEM - Electron Gun

19. SEM - Electromagnetic Condenser Lenses

20. SEM - Electromagnetic Condenser Lenses

21. SEM - Objective Len 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.

22. SEM - Electron Probe

23. SEM - Image Formation-1

24. SEM - Image Formation-2

25. high voltage low voltage Scanning Electron Microscopy Effect of accelerating voltage http://www.jeol.com/sem_gde/imgchng.html

26. Scanning Electron Microscopy Effect of accelerating voltage http://www.jeol.com/sem_gde/imgchng.html

27. Scanning Electron Microscopy Effect of beam current and spot size http://www.jeol.com/sem_gde/imgchng.html

28. Scanning Electron Microscopy Effect of accelerating voltage http://www.jeol.com/sem_gde/imgchng.html

29. Scanning Electron Microscopy Effect of accelerating voltage http://www.jeol.com/sem_gde/imgchng.html

30. Scanning Electron Microscopy Incorrect alignment of objective aperture http://www.jeol.com/sem_gde/imgchng.html

31. Scanning Electron Microscopy Effect of specimen tilt http://www.jeol.com/sem_gde/imgchng.html Stereo microscopy

32. Scanning Electron Microscopy (1) Effect of accelerating voltage (2) (3) http://www.jeol.com/sem_gde/imgchng.html

33. Scanning Electron Microscopy Contrast and brightness http://www.jeol.com/sem_gde/imgchng.html

34. http://www.jeol.com/sem_gde/imgchng.html Scanning Electron Microscopy Astigmatism

35. Scanning Electron Microscopy Sample charging http://www.jeol.com/sem_gde/imgchng.html

36. Scanning Electron Microscopy Preventing charging by thin film coating http://www.jeol.com/sem_gde/imgchng.html

37. Scanning Electron Microscopy Electron beam damages and contamination Carbon contaminant deposited by electron beam http://www.jeol.com/sem_gde/imgchng.html Electron beam damage on a fly’s compound eye

38. Scanning Electron Microscopy Sources of image distortions http://www.jeol.com/sem_gde/imgchng.html

39. Scanning Electron Microscopy Influence of external disturbances http://www.jeol.com/sem_gde/imgchng.html

40. http://www.jeol.com/sem_gde/imgchng.html Scanning Electron Microscopy Importance of sample preparation

41. Electron-Specimen Interaction backscattered e- elemental contrast e- e- secondary e- surface topography e- Primary or unscattered e- projected sample image transmission electron microscopy http://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

42. Electron-Specimen Interaction Principle of E. M. lithography Polymer resist Substrate

43. Electron Beam Lithography Micropatterning and Microfabrication E-beam develop resist selectively etch substrate PMMA resist http://www.cnf.cornell.edu/SPIEBook/spie5.htm#2.5.3.1

44. Microfabricated Catalysts 50 nm nickel, 50 nm SiO2 deposit alternate layers of catalyst and inert micropattern and etch undercut and remove

45. Supported Catalysts Metal supported on metal oxide Coarsening

46. Microfabricated Catalysts Zeolite micropatterned catalysts Zeolite Grids Zeolite Grids (200)/(020) (101)

47. Electron beam Thin sample Unscattered electrons Electron-Specimen Interaction

48. Different Types of Electron Microscopy TEM Ultra-TEM SEM HREM

49. Transmission Electron Microscopy Au/SiO2 http://www.mwrn.com/guide.htm http://www.hei.org/research/depts/aemi/micro.htm

50. Electron-Specimen Interaction