Fracture mechanics of delamination defects in multilayer dielectric coatings.
During the fabrication of multilayer-dielectric (MLD) thin-film-coated optics, such as the diffraction gratings used in OMEGA EP's pulse compressors, acid piranha cleaning can lead to the formation of chemically induced delamination defects. We investigate the causes of these defects and describe a mechanism for the deformation and failure of the MLD coating in response to hydrogen peroxide in the cleaning solution. A fracture mechanics model is developed and used to calculate the crack path that maximizes the energy-release rate, which is found to be consistent with the characteristic fracture pattern observed in MLD coating delamination defects.
H P H
HP
Liddell
K
K
Mehrotra
J C
JC
Lambropoulos
S D
SD
Jacobs