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!