Pyramidal structural defects in erbium silicide thin films
  A new pyramidal structural defect, 5 to 8 micron wide, has been discovered in thin films of epitaxial erbium disilicide formed by annealing thin Er films on Si(001) substrates at temperatures of 500 to 800C. Since these defects form even upon annealing in vacuum of TiN-capped films their formation is not due to oxidation. The pyramidal defects are absent when the erbium disilicide forms on amorphous substrates, which suggests that epitaxial strains play an important role in their formation. We propose that these defects form as a result of the separation of the silicide film from the substrate and its buckling in order to relieve the compressive, biaxial epitaxial stresses. Silicon can then diffuse through the silicide or along the interface to fully or partially fill the void between the buckled erbium disilicide film and the substrate. 
Eu Jin Tan, Mathieu Bouville, Dong Zhi Chi, Kin Leong Pey, Pooi See   Lee, David J. Srolovitz, Chih Hang Tung, and Lei Jun Tang