1. Preparation of cross-section TEM specimen on sapphire substrate
Tian Li
Institute of Physics, Warsaw

2. Importance and purpose
No good specimen preparation, no reliable TEM study
A good TEM specimen should :
Have relatively large area of electron transparency thickness (~10 to 100 nm).
Have as less artifact as possible in order to represent the true nature of a material
Be electronically conductive
Be free of oxidation and hydrocarbonate contamination

3. General procedures Cutting wafer and stacking Slicing and grinding
Mechanical polishing by dimpling
Electronically polishing by ion milling
Post-preparation and prior-measurement treatment

4. General procedures Cutting wafer and stacking Slicing and grinding
Mechanical polishing by dimpling
Electronically polishing by ion milling
Post-preparation and prior-measurement treatment

5. Cutting two pieces from wafer
[10-10]
(The drawing is not to scale)

6. Cutting two pieces from wafer
Size:
2.7mm×6mm

7. Glue two pieces into a stack
Paste
Glue should be:
1.Strong enough; 2.Homogeneously spread;3. As thin as possible

8. General procedures Cutting wafer and stacking Slicing and grinding
Mechanical polishing by dimpling
Electronically polishing by ion milling
Post-preparation and prior-measurement treatment

9. Slicing by diamond wire saw
[0001]
Diamond wire saw
Thickness:
~500 mm

10. Mechanically grinding
Holder of grinding

11. Mechanically grinding

12. Mechanically grinding
Thickness:
80~100 mm

13. Mechanically grinding
Film
Specimen
30 micron
> 120 micron
15 micron
Remove 20 micron
6 micron
3 minutes
3 micron
Diamond lapping film

14. General procedures Cutting wafer and stacking Slicing and grinding
Mechanical polishing by dimpling
Electronically polishing by ion milling
Post-preparation and prior-measurement treatment

15. Dimpling instrument
Force
Speed
Gatan dimple grinder 656

16. Dimpling geometry Dimpling Dimpling specimen Thinner to 30~35mm
Diamond paste
Dimpling
Dimpling
specimen
Thinner to 30~35mm
Glass cylinder

17. Polishing Dimpling 30~35mm Further thin to 20~25mm by
cotton with 6mm diamond paste
for 30 minutes
Polishing by cotton with 3mm
paste for 5 minutes

18. General procedures Cutting wafer and stacking Slicing and grinding
Mechanical polishing by dimpling
Electronically polishing by ion milling
Post-preparation and prior-measurement treatment

19. Ion milling by Gatan Pips
691
precision ion polishing system
Ion milling
Slot size: 1.0 × 1.5 mm
Material: Molybdenum

20. Ion milling by Gatan Pips
Gun
Argon plasma
Incident angle: 5~8 
Gun voltage: 4kV

21. Ion milling by Gatan Pips

22. Ion milling by Gatan Pips
Gun
Argon plasma
Incident angle: 5~8 
Gun voltage: 4kV
200V for 10 minutes

23. General procedures Cutting wafer and stacking Slicing and grinding
Mechanical polishing by dimpling
Electronically polishing by ion milling
Post-preparation and prior-measurement treatment

24. Coating with conductive materialsSi
Evaporation or deposition thin layer of carbon or gold a few nanometers to make specimen electronically conductive.

25. Plasma cleaning and re-etching
In principle, the specimen should be kept in a vaccum. The specimen in the air can be contaminated by hydrocarbonates, and/or degraded by oxidation.
Hydrocarbon contamination can be removed by plasma prior to TEM investigation.
Oxidation or other chemical processes have to be removed by re-etching in ion milling machine, usually with lower Gun voltage of Argon plasma. (Gun 300 Volts 10 minutes)

26. TEM/STEM images
HRTEM
STEM/HAADF

27. Thank you very much!