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Preparation of cross-section TEM specimen on sapphire substrate
Tian LiInstitute of Physics, Warsaw
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
General procedures
• Cutting wafer and stacking• Slicing and grinding • Mechanical polishing by dimpling • Electronically polishing by ion milling• Post-preparation and prior-measurement
treatment
General procedures
• Cutting wafer and stacking• Slicing and grinding • Mechanical polishing by dimpling • Electronically polishing by ion milling• Post-preparation and prior-measurement
treatment
Cutting two pieces from wafer
[10-10]
(The drawing is not to scale)
Cutting two pieces from wafer
Size:
2.7mm×6mm
Glue two pieces into a stack
Paste
Glue should be:1.Strong enough; 2.Homogeneously spread;3. As thin as possible
General procedures
• Cutting wafer and stacking• Slicing and grinding • Mechanical polishing by dimpling • Electronically polishing by ion milling• Post-preparation and prior-measurement
treatment
Slicing by diamond wire saw
[0001]
Thickness:~500 m
Diamond wire sawDiamond wire saw
Mechanically grinding
Holder of grinding
Mechanically grinding
Mechanically grinding
Thickness:80~100 m
Mechanically grinding
Diamond lapping film
Film Specimen
30 micron > 120 micron
15 micron Remove 20 micron
6 micron 3 minutes
3 micron 3 minutes
General procedures
• Cutting wafer and stacking• Slicing and grinding • Mechanical polishing by dimpling • Electronically polishing by ion milling• Post-preparation and prior-measurement
treatment
Dimpling instrument
Gatan dimple grinder 656
Speed
Force
Dimpling geometry
Glass cylinderGlass cylinder Thinner to 30~35m
DimplingDimpling
Diamond pasteDiamond paste
•Further thin to 20~25m by cotton with 6m diamond pastefor 30 minutes
30~35m
Dimpling
Polishing
• Polishing by cotton with 3m paste for 5 minutes
General procedures
• Cutting wafer and stacking• Slicing and grinding • Mechanical polishing by dimpling • Electronically polishing by ion milling• Post-preparation and prior-measurement
treatment
Ion milling by Gatan Pips
Slot size: 1.0 × 1.5 mm
Material: Molybdenum
Ion milling
Gatan PIPS691
precision ion polishing system
Ion milling by Gatan Pips
Incident angle: 5~8 Gun voltage: 4kV
Gun
Argon plasma
Ion milling by Gatan Pips
Ion milling by Gatan Pips
Incident angle: 5~8 Gun voltage: 4kV
Gun
Argon plasma
200V for 10 minutes
General procedures
• Cutting wafer and stacking• Slicing and grinding • Mechanical polishing by dimpling • Electronically polishing by ion milling• Post-preparation and prior-measurement
treatment
Coating with conductive materials
Evaporation or deposition thin layer of carbon or gold a few nanometers to make specimen electronically conductive.
Si
• 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)
Plasma cleaning and re-etching
TEM/STEM images
HRTEM STEM/HAADF
Thank you very much!