Thin Metal Foils with Coatings - Sample Preparation for SEM

Application Note for Leica EM RES102 - Material Research

October 05, 2016

Thin foils are mostly unstable because of their thickness of a few microns. This makes it difficult to do slope cutting without any protection of the sample.

A common realisation to protect the sample surface is by sticking a cover glass on top of the sample.

Another issue is cutting the foils before ion milling. The sample edge should be flat and sharp without any broken areas. A razor blade is mostly the best solution.
A protected sample can salso be sawed with a wire saw.

Cross sectioning of copper foil with lithium layer

The sample is just 46 µm thick and difficult to handle.

Cross sectioning to obtain information concerning the interface between the copper foil and the Lithium / Carbon layer.

Preparation Conditions
Mechanical pre-preparation
Cut the foil with a razor blade to get the appropriate sample size and a flat sample edge.

Ion Milling

Acceleration voltage:7 kV
Current:2.6 mA
Oscillation angle:±40°
Milling time:3 h

- Cut is very flat and clean
- Grain structure of copper and the Lithium / Carbon layer is clearly visible
- Interface structure is clearly recognizable

Fig.1: Cross section of a Cu foil with Lithium / Carbon layer

Cross sectioning of Sn on Cu

Cu and Sn are very soft. They are very difficult to prepare in a conventional way.

Cross sectioning to obtain information regarding the grain structure of Tin and the interface area.

Preparation Conditions
Mechanical pre-preparation
Cut the foil with a razor blade to achieve the appropriate sample size with a flat milling edge.

Ion milling

Acceleration voltage:6 kV
Gun current:2.6 mA
Milling angle:
Oscillation angle:±35°
Milling time:3.5 h


- The columnar structure of Sn with cracks is visible
- Grain structure and interface structure are clearly visbible
- Voids and Cracks in the interface area
- Grain structure of Cu

Fig.2: Cross section of a Tin layer on a Copper foil (Image: Geoff West, Loughborough University, UK)