Preparation of cross-section TEM specimen on sapphire substrate Tian Li Institute 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] Diamond wire saw Thickness: ~500 mm

Mechanically grinding Holder of grinding

Mechanically grinding

Mechanically grinding Thickness: 80~100 mm

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

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 Force Speed Gatan dimple grinder 656

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

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

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 691 precision ion polishing system Ion milling Slot size: 1.0 × 1.5 mm Material: Molybdenum

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

Ion milling by Gatan Pips

Ion milling by Gatan Pips Gun Argon plasma Incident angle: 5~8  Gun voltage: 4kV 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 Si Evaporation or deposition thin layer of carbon or gold a few nanometers to make specimen electronically conductive.

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)

TEM/STEM images HRTEM STEM/HAADF

Thank you very much!