MECHANICAL-PROPERTIES OF COATED COPPER MIRRORS

Copper mirrors are generally used in optical systems for handling CO2 laser beams. The presence of a protective coating on the mirror surface is necessary to increase the lifetime of mirrors working in a hostile environment. The mechanical properties (adhesion, hardness and abrasion) of Y2O3 and a-C:H protective thin films on copper mirrors have been investigated. Y2O3 and a-C:H coatings have been deposited by rf sputtering and dual ion beam sputtering, respectively. The coating adhesion has been measured by the 'scratch test' and the 'topple test', while the hardness has been measured with the knoop microindentation technique. In order to estimate the abrasion resistance of the samples, the 'eraser test' has been performed with a custom-made instrument. © 1990.