One of the skin layers,
i.e. the skin layer that is coated with AlOx, can be clearly seen in the lower magnification TEM image and reveals a thickness of less than 0.5 μm.
Here, it is also observable that the AlOx layer fractures during TEM sample preparation, caused by the compression of the
microtoming process and the different elastic properties of the BOPP polymer, the embedding medium and the ceramic AlOx layer