The so-called nano-etching technique was used to determine the dislocation mechanisms which were associated with the pop-in phenomenon. Successive stages of highly controlled chemomechanical polishing revealed that these dislocations were half-loops lying in classical slip systems. However, they did not extend on the surface in a typical rosette-pattern but remained concentrated around the imprint. A mechanism, which involved dislocation interactions that were enhanced by the fact that the dislocations were suddenly nucleated in a small volume, was proposed in order to explain the observed distribution.

Pop-In Phenomenon in MgO and LiF - Observation of Dislocation Structures. Y.Gaillard, C.Tromas, J.Woirgard: Philosophical Magazine Letters, 2003, 83[9], 553-61