Improving TEM specimen preparation of oxides with the help of electron backscatter patterns

Abstract text (incl. figure legends and references)

The quality of the Transmission Electron Microscopy (TEM) specimens is crucial for the quality of results obtainable from a TEM investigation. If Focused Ion Beam (FIB) milling is used for the preparation, the major limitations in specimen quality are due to a damage layer on the specimen surface, which is induced by interactions between the ion beam and the surface atoms. The processes leading to damage are well known for metals and semiconductors, yet, limited studies investigated the interaction mechanisms between ion beams and oxides with more complex lattice structures such as perovskites. Therefore, we aim at a better understanding of FIB-induced damage of oxide surfaces with this investigation and want to use this knowledge for minimizing the damage layer in FIB-prepared samples.

Various ion-beam-milling conditions, that are typically applied during a TEM specimen preparation process in FIB, were used on oxide specimens regarding their surface damaging behavior. To investigate the amount of surface damage, two different methods were applied: Firstly, TEM images of the damage layers were taken after FIB milling with different acceleration voltages, beam currents, and ion incident angles. The damage layer thickness was directly measured from these images. Secondly, individual electron backscatter patterns (EBSP) and electron backscatter diffraction (EBSD) maps were recorded before and after FIB milling to study the effects on the quality of EBSPs, since this a very sensitive measure of surface distortions. Furthermore, the indexing success of EBSD maps has been investigated with respect to the different milling parameters.

The presentation will summarize the results and discuss strategies for obtaining high quality TEM specimen with minimal surface damage.