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

2. Electron-Specimen Interaction e-e- e-e- e-e- backscattered e - elemental contrast secondary e - surface topography 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. Specimen Interaction Volume (V i ) Auger secondary e- backscattered e- K X-ray L X-ray increasing depth surface information bulk information V i  when accelerating  V i  when incident angle  V i  when atomic number 

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

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 gold TEM

9. Electron-Specimen Interaction e-e- e-e- e-e- X-rays bulk elemental composition Auger electrons surface elemental composition Cathodaluminescence band-gap energy, electronic property 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 Sampling volume for X-ray X-rays Si(Li) detector

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

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

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

16. Electron-Specimen Interaction http://jan.ucc.nau.edu/~wittke/Microprobe/Interact.html#Aug Auger Electron WKWK WLWL WMWM WNWN WGWG KK KK LL Auger e - or Auger e -   Z 

17. Scanning Electron Microscopy specimen Electron gun

18. SEM - Electron Gun

19. SEM - Electromagnetic Condenser Lenses

21. 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

22. SEM - Electron Probe

23. SEM - Image Formation-1

24. SEM - Image Formation-2

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

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

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

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 http://www.jeol.com/sem_gde/imgchng.html Carbon contaminant deposited by electron beam 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. Scanning Electron Microscopy Importance of sample preparation http://www.jeol.com/sem_gde/imgchng.html

41. Electron-Specimen Interaction e-e- e-e- e-e- backscattered e - elemental contrast secondary e - surface topography 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 PMMA resist E-beam develop resist selectively etch substrate http://www.cnf.cornell.edu/SPIEBook/spie5.htm#2.5.3.1

44. Microfabricated Catalysts deposit alternate layers of catalyst and inert micropattern and etch undercut and remove 50 nm nickel, 50 nm SiO 2

45. Supported Catalysts Metal supported on metal oxide Coarsening

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

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

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

49. Transmission Electron Microscopy Au/SiO 2 http://www.mwrn.com/guide.htm http://www.hei.org/research/depts/aemi/micro.htm

50. Electron-Specimen Interaction

51. Transmission Electron Microscopy Au

52. Transmission Electron Microscopy Primary or unscattered electrons diamond gold TEM http://em-outreach.sdsc.edu/web-course

53. Transmission Electron Microscopy Catalyst particle size distribution

54. Transmission Electron Microscopy Catalyst particle shape and morphology

55. Particle Morphology Selected zone dark field imaging (SZDF) ? ?

56. Particle Morphology Selected zone dark field imaging (SZDF)  (100) (110)

57. Particle Morphology Weak beam dark field (WBDF) 

58. Particle Morphology SZDF and WBDF techniques

59. Electron-Specimen Interaction

60. Transmission Electron Microscopy Distribution of crystallographic planes

61. Electron-Specimen Interaction

62. High Resolution Electron Microscopy http://bnlstb.bio.bnl.gov/biodocs/stem/interactive.htmlx Bismuth molybdates (Bi 2 Mo 3 O 12 -  )

63. High Resolution Electron Microscopy Bismuth molybdates (Bi 2 MoO 6 -  )

64. High Resolution Electron Microscopy Platinum on Alumina hydrogen Hydrogen sulfide

65. High Resolution Electron Microscopy 2 x 1 reconstruction of (110) surface of Au particle

66. High Resolution Electron Microscopy Rh/SiO 2 Reduced Oxidized

67. High Resolution Electron Microscopy Rh particles

68. High Resolution Electron Microscopy Electron-beam induced reduction of RuCl 3 on MgO

69. High Resolution Electron Microscopy Hydrogen reduced Rhodium-TiO 2

70. Electron-Specimen Interaction